use std::path::PathBuf;

use disasmer_core::{
    Capability, CommandBackendKind, CommandInvocation, CommandPlan, DebugEpoch, DebugParticipant,
    DebugParticipantKind, DebugRuntimeState, Digest, EnvironmentKind, GuestRuntimeKind, LogBuffer,
    NativeCommandPolicy, NodeId, ProcessId, TaskId, VfsManifest, VfsObject, VfsOverlay, VfsPath,
};
use serde::{Deserialize, Serialize};
use thiserror::Error;
use wasmtime::{
    Caller, Config, DebugEvent, DebugHandler, Engine, Instance, Linker, Module, OptLevel, Store,
    StoreContextMut,
};

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct MaterializedEnvironment {
    pub name: String,
    pub backend: CommandBackendKind,
    pub local_reference: String,
}

#[derive(Clone, Debug, Error, PartialEq, Eq)]
pub enum BackendError {
    #[error("native command denied: {0}")]
    Denied(String),
    #[error("environment is required for this backend")]
    MissingEnvironment,
    #[error("command failed to execute: {0}")]
    Command(String),
    #[error("artifact staging failed: {0}")]
    Artifact(String),
    #[error("unsupported environment kind for backend")]
    UnsupportedEnvironment,
    #[error("node cannot freeze task `{task}` for the current debug epoch")]
    DebugFreezeUnsupported { task: TaskId },
}

pub trait CommandBackend {
    fn kind(&self) -> CommandBackendKind;
    fn plan(&self, invocation: &CommandInvocation) -> Result<CommandPlan, BackendError>;
}

#[derive(Clone, Debug, Default)]
pub struct LinuxRootlessPodmanBackend;

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct PodmanCommand {
    pub program: String,
    pub args: Vec<String>,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct ProcessOutput {
    pub status_code: Option<i32>,
    pub stdout: Vec<u8>,
    pub stderr: Vec<u8>,
}

pub trait ProcessRunner {
    fn run(&mut self, command: &PodmanCommand) -> Result<ProcessOutput, BackendError>;
}

#[derive(Clone, Debug, Default)]
pub struct StdProcessRunner;

impl ProcessRunner for StdProcessRunner {
    fn run(&mut self, command: &PodmanCommand) -> Result<ProcessOutput, BackendError> {
        let output = std::process::Command::new(&command.program)
            .args(&command.args)
            .output()
            .map_err(|err| BackendError::Command(format!("{err:#}")))?;

        Ok(ProcessOutput {
            status_code: output.status.code(),
            stdout: output.stdout,
            stderr: output.stderr,
        })
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct PodmanEnvironmentMaterialization {
    pub environment: String,
    pub image_tag: String,
    pub build: PodmanCommand,
    pub rootless_user_podman: bool,
    pub embeds_full_image_in_bundle: bool,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct LocalSourceCheckout {
    pub host_path: PathBuf,
    pub snapshot: Digest,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub enum SourceAccessMode {
    LocalCheckoutBindMount {
        host_path: PathBuf,
        container_path: String,
        read_only: bool,
        snapshot: Digest,
    },
    NodePreparedSnapshot {
        node_path: PathBuf,
        container_path: String,
        snapshot: Digest,
    },
}

impl SourceAccessMode {
    pub fn uses_full_repo_tarball(&self) -> bool {
        false
    }

    pub fn coordinator_routed_file_reads(&self) -> bool {
        false
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub enum LinuxTaskState {
    Running,
    Frozen,
    Cancelled,
    Completed,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct LinuxTaskLifecycle {
    pub process: ProcessId,
    pub virtual_thread: TaskId,
    pub log_stream: String,
    pub cancellation_token: String,
    pub debug_participant: String,
    pub freeze_supported: bool,
    pub state: LinuxTaskState,
}

impl LinuxTaskLifecycle {
    pub fn new(process: ProcessId, virtual_thread: TaskId) -> Self {
        Self {
            log_stream: format!("process/{process}/task/{virtual_thread}/logs"),
            cancellation_token: format!("cancel:{process}:{virtual_thread}"),
            debug_participant: format!("debug:{process}:{virtual_thread}"),
            process,
            virtual_thread,
            freeze_supported: true,
            state: LinuxTaskState::Running,
        }
    }

    pub fn freeze_for_debug_epoch(&mut self) -> Result<(), BackendError> {
        if !self.freeze_supported {
            return Err(BackendError::DebugFreezeUnsupported {
                task: self.virtual_thread.clone(),
            });
        }
        self.state = LinuxTaskState::Frozen;
        Ok(())
    }

    pub fn resume_after_debug_epoch(&mut self) {
        if self.state == LinuxTaskState::Frozen {
            self.state = LinuxTaskState::Running;
        }
    }

    pub fn cancel(&mut self) {
        self.state = LinuxTaskState::Cancelled;
    }

    pub fn complete(&mut self) {
        self.state = LinuxTaskState::Completed;
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct LinuxCommandRunPlan {
    pub process: ProcessId,
    pub virtual_thread: TaskId,
    pub image_tag: String,
    pub run: PodmanCommand,
    pub source_access: SourceAccessMode,
    pub stage_stdout_as: Option<VfsPath>,
    pub uses_full_repo_tarball: bool,
    pub coordinator_routed_file_reads: bool,
    pub lifecycle: LinuxTaskLifecycle,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct LinuxCommandTaskOutput {
    pub virtual_thread: TaskId,
    pub status_code: Option<i32>,
    pub stdout: String,
    pub stderr: String,
    pub stdout_truncated: bool,
    pub stderr_truncated: bool,
    pub log_backpressured: bool,
    pub staged_artifact: Option<VfsObject>,
    pub lifecycle: LinuxTaskLifecycle,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct CapturedCommandLogs {
    pub stdout: String,
    pub stderr: String,
    pub stdout_truncated: bool,
    pub stderr_truncated: bool,
    pub backpressured: bool,
}

pub const DEFAULT_COMMAND_LOG_LIMIT_BYTES: usize = 256 * 1024;

impl LinuxRootlessPodmanBackend {
    pub fn materialize_environment(
        &self,
        env: &disasmer_core::EnvironmentResource,
    ) -> Result<PodmanEnvironmentMaterialization, BackendError> {
        match env.kind {
            EnvironmentKind::Containerfile | EnvironmentKind::Dockerfile => {}
            EnvironmentKind::NixFlake => return Err(BackendError::UnsupportedEnvironment),
        }

        let image_tag = self.image_tag(env);
        Ok(PodmanEnvironmentMaterialization {
            environment: env.name.clone(),
            image_tag: image_tag.clone(),
            build: PodmanCommand {
                program: "podman".to_owned(),
                args: vec![
                    "build".to_owned(),
                    "--pull=never".to_owned(),
                    "--tag".to_owned(),
                    image_tag,
                    "--file".to_owned(),
                    env.recipe_path.to_string_lossy().into_owned(),
                    env.context_path.to_string_lossy().into_owned(),
                ],
            },
            rootless_user_podman: true,
            embeds_full_image_in_bundle: false,
        })
    }

    pub fn plan_local_checkout_run(
        &self,
        process: ProcessId,
        virtual_thread: TaskId,
        invocation: &CommandInvocation,
        checkout: LocalSourceCheckout,
        stage_stdout_as: Option<VfsPath>,
    ) -> Result<LinuxCommandRunPlan, BackendError> {
        let env = invocation
            .env
            .as_ref()
            .ok_or(BackendError::MissingEnvironment)?;
        let materialization = self.materialize_environment(env)?;
        let source_access = SourceAccessMode::LocalCheckoutBindMount {
            host_path: checkout.host_path.clone(),
            container_path: "/workspace".to_owned(),
            read_only: false,
            snapshot: checkout.snapshot,
        };
        let lifecycle = LinuxTaskLifecycle::new(process.clone(), virtual_thread.clone());
        let mut args = vec![
            "run".to_owned(),
            "--rm".to_owned(),
            "--network".to_owned(),
            "none".to_owned(),
            "--volume".to_owned(),
            format!("{}:/workspace:Z", checkout.host_path.to_string_lossy()),
            "--workdir".to_owned(),
            "/workspace".to_owned(),
            materialization.image_tag.clone(),
            invocation.program.clone(),
        ];
        args.extend(invocation.args.iter().cloned());

        Ok(LinuxCommandRunPlan {
            process,
            virtual_thread,
            image_tag: materialization.image_tag,
            run: PodmanCommand {
                program: "podman".to_owned(),
                args,
            },
            source_access,
            stage_stdout_as,
            uses_full_repo_tarball: false,
            coordinator_routed_file_reads: false,
            lifecycle,
        })
    }

    pub fn execute_environment_materialization(
        &self,
        env: &disasmer_core::EnvironmentResource,
        runner: &mut impl ProcessRunner,
    ) -> Result<MaterializedEnvironment, BackendError> {
        let materialization = self.materialize_environment(env)?;
        let output = runner.run(&materialization.build)?;
        if output.status_code != Some(0) {
            return Err(BackendError::Command(format!(
                "podman build for environment `{}` failed with status {:?}: {}",
                materialization.environment,
                output.status_code,
                String::from_utf8_lossy(&output.stderr)
            )));
        }

        Ok(MaterializedEnvironment {
            name: materialization.environment,
            backend: CommandBackendKind::LinuxRootlessPodman,
            local_reference: materialization.image_tag,
        })
    }

    pub fn execute_run_plan(
        &self,
        plan: LinuxCommandRunPlan,
        runner: &mut impl ProcessRunner,
        overlay: &mut VfsOverlay,
    ) -> Result<LinuxCommandTaskOutput, BackendError> {
        self.execute_run_plan_with_log_limit(plan, runner, overlay, DEFAULT_COMMAND_LOG_LIMIT_BYTES)
    }

    pub fn execute_run_plan_with_log_limit(
        &self,
        mut plan: LinuxCommandRunPlan,
        runner: &mut impl ProcessRunner,
        overlay: &mut VfsOverlay,
        max_log_bytes: usize,
    ) -> Result<LinuxCommandTaskOutput, BackendError> {
        let output = runner.run(&plan.run)?;
        let logs = capture_command_logs(
            &plan.virtual_thread,
            &output.stdout,
            &output.stderr,
            max_log_bytes,
        );
        let staged_artifact = if output.status_code == Some(0) {
            if let Some(path) = plan.stage_stdout_as.take() {
                Some(overlay.write(
                    path,
                    Digest::sha256(&output.stdout),
                    output.stdout.len() as u64,
                ))
            } else {
                None
            }
        } else {
            None
        };

        if output.status_code == Some(0) {
            plan.lifecycle.complete();
        }

        Ok(LinuxCommandTaskOutput {
            virtual_thread: plan.virtual_thread,
            status_code: output.status_code,
            stdout: logs.stdout,
            stderr: logs.stderr,
            stdout_truncated: logs.stdout_truncated,
            stderr_truncated: logs.stderr_truncated,
            log_backpressured: logs.backpressured,
            staged_artifact,
            lifecycle: plan.lifecycle,
        })
    }

    pub fn execute_local_checkout_task(
        &self,
        process: ProcessId,
        virtual_thread: TaskId,
        invocation: &CommandInvocation,
        checkout: LocalSourceCheckout,
        stage_stdout_as: Option<VfsPath>,
        runner: &mut impl ProcessRunner,
        overlay: &mut VfsOverlay,
    ) -> Result<LinuxCommandTaskOutput, BackendError> {
        let env = invocation
            .env
            .as_ref()
            .ok_or(BackendError::MissingEnvironment)?;
        self.execute_environment_materialization(env, runner)?;
        let plan = self.plan_local_checkout_run(
            process,
            virtual_thread,
            invocation,
            checkout,
            stage_stdout_as,
        )?;
        self.execute_run_plan(plan, runner, overlay)
    }

    fn image_tag(&self, env: &disasmer_core::EnvironmentResource) -> String {
        let name = env
            .name
            .chars()
            .map(|ch| {
                if ch.is_ascii_alphanumeric() || ch == '-' || ch == '_' {
                    ch
                } else {
                    '-'
                }
            })
            .collect::<String>();
        let digest = env
            .digest
            .as_str()
            .chars()
            .map(|ch| {
                if ch.is_ascii_alphanumeric() || ch == '-' || ch == '_' || ch == '.' {
                    ch
                } else {
                    '-'
                }
            })
            .take(24)
            .collect::<String>();
        format!("disasmer-env/{name}:{digest}")
    }
}

impl CommandBackend for LinuxRootlessPodmanBackend {
    fn kind(&self) -> CommandBackendKind {
        CommandBackendKind::LinuxRootlessPodman
    }

    fn plan(&self, invocation: &CommandInvocation) -> Result<CommandPlan, BackendError> {
        let env = invocation
            .env
            .as_ref()
            .ok_or(BackendError::MissingEnvironment)?;
        match env.kind {
            EnvironmentKind::Containerfile | EnvironmentKind::Dockerfile => Ok(CommandPlan {
                guest_runtime: GuestRuntimeKind::Wasmtime,
                backend: CommandBackendKind::LinuxRootlessPodman,
                required_capability: Capability::RootlessPodman,
                user_attached_development_execution: false,
            }),
            EnvironmentKind::NixFlake => Err(BackendError::UnsupportedEnvironment),
        }
    }
}

#[derive(Clone, Debug, Default)]
pub struct WindowsCommandDevBackend;

impl CommandBackend for WindowsCommandDevBackend {
    fn kind(&self) -> CommandBackendKind {
        CommandBackendKind::WindowsCommandDev
    }

    fn plan(&self, _invocation: &CommandInvocation) -> Result<CommandPlan, BackendError> {
        Ok(CommandPlan {
            guest_runtime: GuestRuntimeKind::Wasmtime,
            backend: CommandBackendKind::WindowsCommandDev,
            required_capability: Capability::WindowsCommandDev,
            user_attached_development_execution: true,
        })
    }
}

#[derive(Clone, Debug, Default)]
pub struct WindowsSandboxStubBackend;

impl CommandBackend for WindowsSandboxStubBackend {
    fn kind(&self) -> CommandBackendKind {
        CommandBackendKind::StubbedWindowsSandbox
    }

    fn plan(&self, _invocation: &CommandInvocation) -> Result<CommandPlan, BackendError> {
        Err(BackendError::Denied(
            "Windows sandbox backend is an explicit stub for MVP; use windows-command-dev only for user-attached development execution"
                .to_owned(),
        ))
    }
}

pub fn authorize_node_command(
    hosted_control_plane: bool,
    node_has_command_capability: bool,
) -> Result<(), BackendError> {
    NativeCommandPolicy {
        hosted_control_plane,
        node_has_command_capability,
    }
    .authorize()
    .map_err(BackendError::Denied)
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct VirtualThreadCommand {
    pub virtual_thread: TaskId,
    pub invocation: CommandInvocation,
    pub stage_stdout_as: Option<VfsPath>,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct CommandOutput {
    pub virtual_thread: TaskId,
    pub status_code: Option<i32>,
    pub stdout: String,
    pub stderr: String,
    pub stdout_truncated: bool,
    pub stderr_truncated: bool,
    pub log_backpressured: bool,
    pub staged_artifact: Option<VfsObject>,
}

#[derive(Clone, Debug)]
pub struct LocalCommandExecutor {
    pub node: NodeId,
    pub hosted_control_plane: bool,
    pub has_command_capability: bool,
}

impl LocalCommandExecutor {
    pub fn run(
        &self,
        command: VirtualThreadCommand,
        overlay: &mut VfsOverlay,
    ) -> Result<CommandOutput, BackendError> {
        self.run_with_log_limit(command, overlay, DEFAULT_COMMAND_LOG_LIMIT_BYTES)
    }

    pub fn run_with_log_limit(
        &self,
        command: VirtualThreadCommand,
        overlay: &mut VfsOverlay,
        max_log_bytes: usize,
    ) -> Result<CommandOutput, BackendError> {
        authorize_node_command(self.hosted_control_plane, self.has_command_capability)?;

        let output = std::process::Command::new(&command.invocation.program)
            .args(&command.invocation.args)
            .output()
            .map_err(|err| BackendError::Command(format!("{err:#}")))?;

        let logs = capture_command_logs(
            &command.virtual_thread,
            &output.stdout,
            &output.stderr,
            max_log_bytes,
        );
        let staged_artifact = if let Some(path) = command.stage_stdout_as {
            Some(overlay.write(
                path,
                Digest::sha256(&output.stdout),
                output.stdout.len() as u64,
            ))
        } else {
            None
        };

        Ok(CommandOutput {
            virtual_thread: command.virtual_thread,
            status_code: output.status.code(),
            stdout: logs.stdout,
            stderr: logs.stderr,
            stdout_truncated: logs.stdout_truncated,
            stderr_truncated: logs.stderr_truncated,
            log_backpressured: logs.backpressured,
            staged_artifact,
        })
    }
}

fn capture_command_logs(
    task: &TaskId,
    stdout: &[u8],
    stderr: &[u8],
    max_log_bytes: usize,
) -> CapturedCommandLogs {
    let mut logs = LogBuffer::new(max_log_bytes);
    logs.push(task.clone(), stdout);
    logs.push(task.clone(), stderr);
    let records = logs.records();
    let stdout_record = &records[0];
    let stderr_record = &records[1];
    debug_assert_eq!(&stdout_record.task, task);
    debug_assert_eq!(&stderr_record.task, task);
    CapturedCommandLogs {
        stdout: String::from_utf8_lossy(&stdout_record.bytes).into_owned(),
        stderr: String::from_utf8_lossy(&stderr_record.bytes).into_owned(),
        stdout_truncated: stdout_record.truncated,
        stderr_truncated: stderr_record.truncated,
        backpressured: logs.backpressured(),
    }
}

#[derive(Clone)]
pub struct WasmtimeTaskRuntime {
    engine: Engine,
}

#[derive(Clone, Debug, Error, PartialEq, Eq)]
pub enum WasmTaskError {
    #[error("wasmtime task failed: {0}")]
    Runtime(String),
    #[error("wasmtime host command failed: {0}")]
    HostCommand(String),
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct WasmtimeDebugProbe {
    pub task: TaskId,
    pub frozen_state: DebugRuntimeState,
    pub resumed_state: DebugRuntimeState,
    pub result: i32,
    pub stack_frames: Vec<String>,
    pub local_values: Vec<(String, String)>,
    pub wasm_function: Option<String>,
    pub wasm_pc: Option<u32>,
}

#[derive(Clone, Debug, Default, PartialEq, Eq)]
struct WasmtimeFrameSnapshot {
    stack_frames: Vec<String>,
    local_values: Vec<(String, String)>,
    wasm_function: Option<String>,
    wasm_pc: Option<u32>,
}

#[derive(Clone, Debug, Default)]
struct WasmtimeDebugState {
    snapshot: Option<WasmtimeFrameSnapshot>,
}

#[derive(Clone, Debug)]
struct WasmtimeLocalSnapshotHandler {
    export: String,
}

impl DebugHandler for WasmtimeLocalSnapshotHandler {
    type Data = WasmtimeDebugState;

    async fn handle(&self, mut store: StoreContextMut<'_, Self::Data>, event: DebugEvent<'_>) {
        if !matches!(event, DebugEvent::Breakpoint) || store.data().snapshot.is_some() {
            return;
        }

        let mut snapshot = WasmtimeFrameSnapshot {
            stack_frames: vec![format!("{}::wasm_export", self.export)],
            ..WasmtimeFrameSnapshot::default()
        };
        for frame in store.debug_exit_frames().collect::<Vec<_>>() {
            if let Ok(Some((function, pc))) = frame.wasm_function_index_and_pc(&mut store) {
                snapshot.wasm_function = Some(format!("{function:?}"));
                snapshot.wasm_pc = Some(pc);
            }

            if let Ok(count) = frame.num_locals(&mut store) {
                for index in 0..count.min(16) {
                    let value = match frame.local(&mut store, index) {
                        Ok(value) => format!("{value:?}"),
                        Err(err) => format!("<error: {err:#}>"),
                    };
                    snapshot
                        .local_values
                        .push((format!("wasm_local_{index}"), value));
                }
            }
            break;
        }

        if let Some(function) = &snapshot.wasm_function {
            snapshot.stack_frames = vec![format!("{} / {function}", self.export)];
        }
        store.data_mut().snapshot = Some(snapshot);
        if let Some(mut edit) = store.edit_breakpoints() {
            let _ = edit.single_step(false);
        }
    }
}

impl WasmtimeTaskRuntime {
    pub fn new() -> Result<Self, WasmTaskError> {
        let mut config = Config::new();
        config.wasm_backtrace_details(wasmtime::WasmBacktraceDetails::Enable);
        let engine = Engine::new(&config).map_err(wasmtime_error)?;
        Ok(Self { engine })
    }

    fn debug_engine() -> Result<Engine, WasmTaskError> {
        let mut config = Config::new();
        config.debug_info(true);
        config.guest_debug(true);
        config.generate_address_map(true);
        config.cranelift_opt_level(OptLevel::None);
        Engine::new(&config).map_err(wasmtime_error)
    }

    pub fn run_i32_export(
        &self,
        wasm_or_wat: impl AsRef<[u8]>,
        export: &str,
        arg: i32,
    ) -> Result<i32, WasmTaskError> {
        let module = Module::new(&self.engine, wasm_or_wat.as_ref()).map_err(wasmtime_error)?;
        let mut store = Store::new(&self.engine, ());
        let instance = Instance::new(&mut store, &module, &[]).map_err(wasmtime_error)?;
        let func = instance
            .get_typed_func::<i32, i32>(&mut store, export)
            .map_err(wasmtime_error)?;
        func.call(&mut store, arg).map_err(wasmtime_error)
    }

    pub fn freeze_resume_i32_export_probe(
        &self,
        wasm_or_wat: impl AsRef<[u8]>,
        export: &str,
        arg: i32,
    ) -> Result<WasmtimeDebugProbe, WasmTaskError> {
        let task = TaskId::from(export);
        let snapshot = Self::debug_i32_export_snapshot(wasm_or_wat.as_ref(), export, arg)?;
        let mut epoch = DebugEpoch::pause(
            ProcessId::from("wasmtime-debug-probe"),
            1,
            vec![DebugParticipant {
                task: task.clone(),
                name: export.to_owned(),
                kind: DebugParticipantKind::WasmTask,
                can_freeze: true,
                state: DebugRuntimeState::Running,
                stack_frames: snapshot.stack_frames.clone(),
                local_values: snapshot.local_values.clone(),
                task_args: vec![("arg".to_owned(), arg.to_string())],
                handles: Vec::new(),
                command_status: None,
                recent_output: Vec::new(),
            }],
        )
        .map_err(|err| WasmTaskError::Runtime(err.to_string()))?;
        let frozen_state = epoch
            .participant_state(&task)
            .cloned()
            .ok_or_else(|| WasmTaskError::Runtime("Wasm debug participant missing".to_owned()))?;
        let inspection = epoch
            .inspection(&task)
            .map_err(|err| WasmTaskError::Runtime(err.to_string()))?;
        epoch.continue_all();
        let resumed_state = epoch
            .participant_state(&task)
            .cloned()
            .ok_or_else(|| WasmTaskError::Runtime("Wasm debug participant missing".to_owned()))?;
        let result = self.run_i32_export(wasm_or_wat, export, arg)?;

        Ok(WasmtimeDebugProbe {
            task,
            frozen_state,
            resumed_state,
            result,
            stack_frames: inspection.stack_frames,
            local_values: inspection.local_values,
            wasm_function: snapshot.wasm_function,
            wasm_pc: snapshot.wasm_pc,
        })
    }

    fn debug_i32_export_snapshot(
        wasm_or_wat: &[u8],
        export: &str,
        arg: i32,
    ) -> Result<WasmtimeFrameSnapshot, WasmTaskError> {
        let engine = Self::debug_engine()?;
        let module = Module::new(&engine, wasm_or_wat).map_err(wasmtime_error)?;
        let runtime = tokio::runtime::Builder::new_current_thread()
            .enable_all()
            .build()
            .map_err(|err| WasmTaskError::Runtime(format!("create debug runtime: {err:#}")))?;
        let state = runtime.block_on(async {
            let mut store = Store::new(&engine, WasmtimeDebugState::default());
            store.set_debug_handler(WasmtimeLocalSnapshotHandler {
                export: export.to_owned(),
            });
            let instance = Instance::new_async(&mut store, &module, &[])
                .await
                .map_err(wasmtime_error)?;
            if let Some(mut edit) = store.edit_breakpoints() {
                edit.single_step(true).map_err(wasmtime_error)?;
            }
            let func = instance
                .get_typed_func::<i32, i32>(&mut store, export)
                .map_err(wasmtime_error)?;
            let _ = func
                .call_async(&mut store, arg)
                .await
                .map_err(wasmtime_error)?;
            Ok::<_, WasmTaskError>(store.into_data())
        })?;

        state.snapshot.ok_or_else(|| {
            WasmTaskError::Runtime(
                "Wasmtime guest debug did not produce a frame-local snapshot".to_owned(),
            )
        })
    }

    pub fn run_i32_export_with_command_import(
        &self,
        wasm_or_wat: impl AsRef<[u8]>,
        export: &str,
        executor: LocalCommandExecutor,
        command: VirtualThreadCommand,
    ) -> Result<WasmtimeHostCommandResult, WasmTaskError> {
        let module = Module::new(&self.engine, wasm_or_wat.as_ref()).map_err(wasmtime_error)?;
        let mut linker = Linker::new(&self.engine);
        linker
            .func_wrap(
                "disasmer",
                "cmd_run",
                |mut caller: Caller<'_, WasmtimeHostCommandState>| -> i32 {
                    let state = caller.data_mut();
                    match state
                        .executor
                        .run(state.command.clone(), &mut state.overlay)
                    {
                        Ok(output) => {
                            let status_code = output.status_code.unwrap_or(-1);
                            state.output = Some(output);
                            status_code
                        }
                        Err(err) => {
                            state.host_error = Some(err.to_string());
                            -1
                        }
                    }
                },
            )
            .map_err(wasmtime_error)?;
        let task = command.virtual_thread.clone();
        let node = executor.node.clone();
        let state = WasmtimeHostCommandState {
            executor,
            overlay: VfsOverlay::new(task, node),
            command,
            output: None,
            host_error: None,
        };
        let mut store = Store::new(&self.engine, state);
        let instance = linker
            .instantiate(&mut store, &module)
            .map_err(wasmtime_error)?;
        let func = instance
            .get_typed_func::<(), i32>(&mut store, export)
            .map_err(wasmtime_error)?;
        let export_result = func.call(&mut store, ()).map_err(wasmtime_error)?;
        let mut state = store.into_data();
        if let Some(error) = state.host_error.take() {
            return Err(WasmTaskError::HostCommand(error));
        }
        let output = state.output.take().ok_or_else(|| {
            WasmTaskError::HostCommand(
                "wasm task completed without invoking disasmer.cmd_run".to_owned(),
            )
        })?;
        let manifest = state.overlay.flush();
        Ok(WasmtimeHostCommandResult {
            export_result,
            command_output: output,
            manifest,
        })
    }
}

fn wasmtime_error(err: wasmtime::Error) -> WasmTaskError {
    WasmTaskError::Runtime(format!("{err:?}"))
}

#[derive(Clone, Debug)]
struct WasmtimeHostCommandState {
    executor: LocalCommandExecutor,
    overlay: VfsOverlay,
    command: VirtualThreadCommand,
    output: Option<CommandOutput>,
    host_error: Option<String>,
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct WasmtimeHostCommandResult {
    pub export_result: i32,
    pub command_output: CommandOutput,
    pub manifest: VfsManifest,
}

#[cfg(test)]
mod tests {
    use std::collections::VecDeque;
    use std::path::PathBuf;

    use disasmer_core::{
        Digest, EnvironmentRequirements, EnvironmentResource, ProjectId, TenantId,
    };

    use super::*;

    #[derive(Default)]
    struct RecordingRunner {
        commands: Vec<PodmanCommand>,
        outputs: VecDeque<ProcessOutput>,
    }

    impl RecordingRunner {
        fn with_outputs(outputs: impl IntoIterator<Item = ProcessOutput>) -> Self {
            Self {
                commands: Vec::new(),
                outputs: outputs.into_iter().collect(),
            }
        }
    }

    impl ProcessRunner for RecordingRunner {
        fn run(&mut self, command: &PodmanCommand) -> Result<ProcessOutput, BackendError> {
            self.commands.push(command.clone());
            self.outputs.pop_front().ok_or_else(|| {
                BackendError::Command("recording runner has no output queued".to_owned())
            })
        }
    }

    fn success_output(stdout: impl Into<Vec<u8>>) -> ProcessOutput {
        ProcessOutput {
            status_code: Some(0),
            stdout: stdout.into(),
            stderr: Vec::new(),
        }
    }

    fn container_env() -> EnvironmentResource {
        EnvironmentResource {
            name: "linux".to_owned(),
            kind: EnvironmentKind::Containerfile,
            recipe_path: PathBuf::from("envs/linux/Containerfile"),
            context_path: PathBuf::from("envs/linux"),
            digest: Digest::sha256("recipe"),
            requirements: EnvironmentRequirements::linux_container(),
        }
    }

    #[test]
    fn linux_backend_plans_rootless_podman_under_wasmtime_virtual_task() {
        let invocation = CommandInvocation {
            program: "cargo".to_owned(),
            args: vec!["build".to_owned()],
            env: Some(container_env()),
        };
        let plan = LinuxRootlessPodmanBackend.plan(&invocation).unwrap();

        assert_eq!(plan.guest_runtime, GuestRuntimeKind::Wasmtime);
        assert_eq!(plan.backend, CommandBackendKind::LinuxRootlessPodman);
        assert_eq!(plan.required_capability, Capability::RootlessPodman);
    }

    #[test]
    fn linux_backend_materializes_containerfile_with_rootless_podman_without_vendored_image() {
        let env = container_env();
        let materialization = LinuxRootlessPodmanBackend
            .materialize_environment(&env)
            .unwrap();

        assert_eq!(materialization.environment, "linux");
        assert!(materialization.image_tag.starts_with("disasmer-env/linux:"));
        assert_eq!(materialization.image_tag.matches(':').count(), 1);
        assert_eq!(materialization.build.program, "podman");
        assert!(materialization.rootless_user_podman);
        assert!(!materialization.embeds_full_image_in_bundle);
        assert!(materialization.build.args.contains(&"build".to_owned()));
        assert!(materialization
            .build
            .args
            .contains(&"--pull=never".to_owned()));
        assert!(materialization
            .build
            .args
            .contains(&"envs/linux/Containerfile".to_owned()));
        assert!(materialization
            .build
            .args
            .contains(&"envs/linux".to_owned()));
    }

    #[test]
    fn linux_run_plan_keeps_local_checkout_local_and_avoids_coordinator_file_reads() {
        let invocation = CommandInvocation {
            program: "cargo".to_owned(),
            args: vec!["build".to_owned(), "--release".to_owned()],
            env: Some(container_env()),
        };
        let plan = LinuxRootlessPodmanBackend
            .plan_local_checkout_run(
                ProcessId::from("vp"),
                TaskId::from("compile-linux"),
                &invocation,
                LocalSourceCheckout {
                    host_path: PathBuf::from("/work/example"),
                    snapshot: Digest::sha256("checkout"),
                },
                Some(VfsPath::new("/vfs/artifacts/app").unwrap()),
            )
            .unwrap();

        assert_eq!(plan.run.program, "podman");
        assert!(plan.run.args.contains(&"run".to_owned()));
        assert!(plan.run.args.contains(&"--network".to_owned()));
        assert!(plan.run.args.contains(&"none".to_owned()));
        assert!(plan
            .run
            .args
            .contains(&"/work/example:/workspace:Z".to_owned()));
        assert!(plan.run.args.contains(&"cargo".to_owned()));
        assert!(plan.run.args.contains(&"--release".to_owned()));
        assert!(!plan.uses_full_repo_tarball);
        assert!(!plan.coordinator_routed_file_reads);
        assert!(!plan.source_access.uses_full_repo_tarball());
        assert!(!plan.source_access.coordinator_routed_file_reads());
        assert_eq!(
            plan.stage_stdout_as,
            Some(VfsPath::new("/vfs/artifacts/app").unwrap())
        );
        assert_eq!(plan.lifecycle.process, ProcessId::from("vp"));
        assert_eq!(plan.lifecycle.virtual_thread, TaskId::from("compile-linux"));
        assert_eq!(plan.lifecycle.state, LinuxTaskState::Running);

        match &plan.source_access {
            SourceAccessMode::LocalCheckoutBindMount {
                host_path,
                container_path,
                read_only,
                ..
            } => {
                assert_eq!(host_path, &PathBuf::from("/work/example"));
                assert_eq!(container_path, "/workspace");
                assert!(!read_only);
            }
            SourceAccessMode::NodePreparedSnapshot { .. } => {
                panic!("local Linux build should use the node-local checkout")
            }
        }
    }

    #[test]
    fn linux_backend_executes_podman_build_then_run_and_stages_artifact() {
        let invocation = CommandInvocation {
            program: "cargo".to_owned(),
            args: vec!["build".to_owned()],
            env: Some(container_env()),
        };
        let mut runner =
            RecordingRunner::with_outputs([success_output([]), success_output(b"artifact-bytes")]);
        let mut overlay = VfsOverlay::new(TaskId::from("compile-linux"), NodeId::from("node"));

        let output = LinuxRootlessPodmanBackend
            .execute_local_checkout_task(
                ProcessId::from("vp"),
                TaskId::from("compile-linux"),
                &invocation,
                LocalSourceCheckout {
                    host_path: PathBuf::from("/work/demo"),
                    snapshot: Digest::sha256("checkout"),
                },
                Some(VfsPath::new("/vfs/artifacts/app.tar.zst").unwrap()),
                &mut runner,
                &mut overlay,
            )
            .unwrap();
        let manifest = overlay.flush();

        assert_eq!(runner.commands.len(), 2);
        assert_eq!(runner.commands[0].program, "podman");
        assert!(runner.commands[0].args.contains(&"build".to_owned()));
        assert_eq!(runner.commands[1].program, "podman");
        assert!(runner.commands[1].args.contains(&"run".to_owned()));
        assert!(runner.commands[1]
            .args
            .contains(&"/work/demo:/workspace:Z".to_owned()));
        assert_eq!(output.status_code, Some(0));
        assert_eq!(output.stdout, "artifact-bytes");
        assert_eq!(output.lifecycle.state, LinuxTaskState::Completed);
        assert!(output.staged_artifact.is_some());
        assert!(manifest
            .objects
            .contains_key(&VfsPath::new("/vfs/artifacts/app.tar.zst").unwrap()));
        assert!(!manifest.large_bytes_uploaded);
    }

    #[test]
    fn linux_backend_caps_logs_without_truncating_staged_artifact_bytes() {
        let invocation = CommandInvocation {
            program: "cargo".to_owned(),
            args: vec!["build".to_owned()],
            env: Some(container_env()),
        };
        let mut runner =
            RecordingRunner::with_outputs([success_output(b"abcdef"), success_output(b"unused")]);
        let mut overlay = VfsOverlay::new(TaskId::from("compile-linux"), NodeId::from("node"));
        let plan = LinuxRootlessPodmanBackend
            .plan_local_checkout_run(
                ProcessId::from("vp"),
                TaskId::from("compile-linux"),
                &invocation,
                LocalSourceCheckout {
                    host_path: PathBuf::from("/work/demo"),
                    snapshot: Digest::sha256("checkout"),
                },
                Some(VfsPath::new("/vfs/artifacts/app.txt").unwrap()),
            )
            .unwrap();

        let output = LinuxRootlessPodmanBackend
            .execute_run_plan_with_log_limit(plan, &mut runner, &mut overlay, 4)
            .unwrap();

        assert_eq!(output.virtual_thread, TaskId::from("compile-linux"));
        assert_eq!(output.stdout, "abcd");
        assert!(output.stdout_truncated);
        assert!(output.log_backpressured);
        assert_eq!(output.staged_artifact.as_ref().unwrap().size, 6);
    }

    #[test]
    fn failed_podman_materialization_returns_clear_error_before_command_run() {
        let invocation = CommandInvocation {
            program: "cargo".to_owned(),
            args: vec!["build".to_owned()],
            env: Some(container_env()),
        };
        let mut runner = RecordingRunner::with_outputs([ProcessOutput {
            status_code: Some(125),
            stdout: Vec::new(),
            stderr: b"image build failed".to_vec(),
        }]);
        let mut overlay = VfsOverlay::new(TaskId::from("compile-linux"), NodeId::from("node"));

        let error = LinuxRootlessPodmanBackend
            .execute_local_checkout_task(
                ProcessId::from("vp"),
                TaskId::from("compile-linux"),
                &invocation,
                LocalSourceCheckout {
                    host_path: PathBuf::from("/work/demo"),
                    snapshot: Digest::sha256("checkout"),
                },
                Some(VfsPath::new("/vfs/artifacts/app.tar.zst").unwrap()),
                &mut runner,
                &mut overlay,
            )
            .unwrap_err();

        assert!(error.to_string().contains("podman build"));
        assert!(error.to_string().contains("image build failed"));
        assert_eq!(runner.commands.len(), 1);
    }

    #[test]
    fn linux_task_lifecycle_supports_cancel_and_all_stop_freeze_resume() {
        let mut lifecycle =
            LinuxTaskLifecycle::new(ProcessId::from("vp"), TaskId::from("compile-linux"));

        lifecycle.freeze_for_debug_epoch().unwrap();
        assert_eq!(lifecycle.state, LinuxTaskState::Frozen);

        lifecycle.resume_after_debug_epoch();
        assert_eq!(lifecycle.state, LinuxTaskState::Running);

        lifecycle.cancel();
        assert_eq!(lifecycle.state, LinuxTaskState::Cancelled);

        let mut unsupported =
            LinuxTaskLifecycle::new(ProcessId::from("vp"), TaskId::from("native-command"));
        unsupported.freeze_supported = false;
        let error = unsupported.freeze_for_debug_epoch().unwrap_err();
        assert!(matches!(error, BackendError::DebugFreezeUnsupported { .. }));
    }

    #[test]
    fn windows_backend_is_labeled_user_attached_dev_execution() {
        let invocation = CommandInvocation {
            program: "cmd".to_owned(),
            args: vec!["/C".to_owned(), "build.bat".to_owned()],
            env: None,
        };
        let plan = WindowsCommandDevBackend.plan(&invocation).unwrap();

        assert!(plan.user_attached_development_execution);
        assert_eq!(plan.required_capability, Capability::WindowsCommandDev);
    }

    #[test]
    fn hosted_control_plane_native_command_is_denied() {
        let error = authorize_node_command(true, true).unwrap_err();

        assert!(matches!(error, BackendError::Denied(_)));
    }

    #[test]
    fn native_command_is_denied_without_command_capability() {
        let error = authorize_node_command(false, false).unwrap_err();

        assert!(matches!(error, BackendError::Denied(_)));
        assert!(error
            .to_string()
            .contains("lacks native command capability"));
    }

    #[test]
    fn wasmtime_runtime_runs_named_task_export() {
        let runtime = WasmtimeTaskRuntime::new().unwrap();
        let result = runtime
            .run_i32_export(
                r#"
                (module
                  (func (export "task_add_one") (param i32) (result i32)
                    local.get 0
                    i32.const 1
                    i32.add))
                "#,
                "task_add_one",
                41,
            )
            .unwrap();

        assert_eq!(result, 42);
    }

    #[test]
    fn wasmtime_runtime_freezes_and_resumes_wasm_debug_participant() {
        let runtime = WasmtimeTaskRuntime::new().unwrap();
        let probe = runtime
            .freeze_resume_i32_export_probe(
                r#"
                (module
                  (func (export "task_add_one") (param i32) (result i32)
                    local.get 0
                    i32.const 1
                    i32.add))
                "#,
                "task_add_one",
                41,
            )
            .unwrap();

        assert_eq!(probe.task, TaskId::from("task_add_one"));
        assert_eq!(probe.frozen_state, DebugRuntimeState::Frozen);
        assert_eq!(probe.resumed_state, DebugRuntimeState::Running);
        assert_eq!(probe.result, 42);
        assert!(probe
            .stack_frames
            .iter()
            .any(|frame| frame.contains("task_add_one")));
        assert!(probe
            .local_values
            .iter()
            .any(|(name, value)| { name == "wasm_local_0" && value.contains("41") }));
        assert!(probe.wasm_pc.is_some());
    }

    #[cfg(unix)]
    #[test]
    fn wasmtime_task_invokes_native_command_through_node_host_import() {
        let runtime = WasmtimeTaskRuntime::new().unwrap();
        let executor = LocalCommandExecutor {
            node: NodeId::from("node"),
            hosted_control_plane: false,
            has_command_capability: true,
        };
        let result = runtime
            .run_i32_export_with_command_import(
                r#"
                (module
                  (import "disasmer" "cmd_run" (func $cmd_run (result i32)))
                  (func (export "task_calls_command") (result i32)
                    call $cmd_run))
                "#,
                "task_calls_command",
                executor,
                VirtualThreadCommand {
                    virtual_thread: TaskId::from("compile-linux"),
                    invocation: CommandInvocation {
                        program: "sh".to_owned(),
                        args: vec!["-c".to_owned(), "printf wasmtime-host-command".to_owned()],
                        env: None,
                    },
                    stage_stdout_as: Some(
                        VfsPath::new("/vfs/artifacts/wasmtime-host-command.txt").unwrap(),
                    ),
                },
            )
            .unwrap();

        assert_eq!(result.export_result, 0);
        assert_eq!(
            result.command_output.virtual_thread,
            TaskId::from("compile-linux")
        );
        assert_eq!(result.command_output.stdout, "wasmtime-host-command");
        assert_eq!(
            result.command_output.staged_artifact.as_ref().unwrap().path,
            VfsPath::new("/vfs/artifacts/wasmtime-host-command.txt").unwrap()
        );
        assert!(!result.manifest.large_bytes_uploaded);
        assert!(result
            .manifest
            .objects
            .contains_key(&VfsPath::new("/vfs/artifacts/wasmtime-host-command.txt").unwrap()));
    }

    #[cfg(unix)]
    #[test]
    fn wasmtime_host_command_import_respects_node_command_capability() {
        let runtime = WasmtimeTaskRuntime::new().unwrap();
        let executor = LocalCommandExecutor {
            node: NodeId::from("node"),
            hosted_control_plane: false,
            has_command_capability: false,
        };
        let error = runtime
            .run_i32_export_with_command_import(
                r#"
                (module
                  (import "disasmer" "cmd_run" (func $cmd_run (result i32)))
                  (func (export "task_calls_command") (result i32)
                    call $cmd_run))
                "#,
                "task_calls_command",
                executor,
                VirtualThreadCommand {
                    virtual_thread: TaskId::from("compile-linux"),
                    invocation: CommandInvocation {
                        program: "sh".to_owned(),
                        args: vec!["-c".to_owned(), "printf denied".to_owned()],
                        env: None,
                    },
                    stage_stdout_as: None,
                },
            )
            .unwrap_err();

        assert!(error
            .to_string()
            .contains("lacks native command capability"));
    }

    #[cfg(unix)]
    #[test]
    fn native_command_output_is_associated_with_virtual_thread_and_staged_to_vfs() {
        let executor = LocalCommandExecutor {
            node: disasmer_core::NodeId::from("node"),
            hosted_control_plane: false,
            has_command_capability: true,
        };
        let mut overlay = VfsOverlay::new(TaskId::from("compile-linux"), NodeId::from("node"));
        let output = executor
            .run(
                VirtualThreadCommand {
                    virtual_thread: TaskId::from("compile-linux"),
                    invocation: CommandInvocation {
                        program: "sh".to_owned(),
                        args: vec![
                            "-c".to_owned(),
                            "printf artifact; printf log >&2".to_owned(),
                        ],
                        env: None,
                    },
                    stage_stdout_as: Some(VfsPath::new("/vfs/artifacts/app.txt").unwrap()),
                },
                &mut overlay,
            )
            .unwrap();
        let manifest = overlay.flush();

        assert_eq!(output.virtual_thread, TaskId::from("compile-linux"));
        assert_eq!(output.stdout, "artifact");
        assert_eq!(output.stderr, "log");
        assert!(output.staged_artifact.is_some());
        assert!(!manifest.large_bytes_uploaded);
        assert!(manifest
            .objects
            .contains_key(&VfsPath::new("/vfs/artifacts/app.txt").unwrap()));
    }

    #[cfg(unix)]
    #[test]
    fn local_command_executor_caps_logs_and_reports_backpressure_by_virtual_thread() {
        let executor = LocalCommandExecutor {
            node: disasmer_core::NodeId::from("node"),
            hosted_control_plane: false,
            has_command_capability: true,
        };
        let mut overlay = VfsOverlay::new(TaskId::from("compile-linux"), NodeId::from("node"));
        let output = executor
            .run_with_log_limit(
                VirtualThreadCommand {
                    virtual_thread: TaskId::from("compile-linux"),
                    invocation: CommandInvocation {
                        program: "sh".to_owned(),
                        args: vec!["-c".to_owned(), "printf abcdef; printf err >&2".to_owned()],
                        env: None,
                    },
                    stage_stdout_as: None,
                },
                &mut overlay,
                4,
            )
            .unwrap();

        assert_eq!(output.virtual_thread, TaskId::from("compile-linux"));
        assert_eq!(output.stdout, "abcd");
        assert_eq!(output.stderr, "");
        assert!(output.stdout_truncated);
        assert!(output.stderr_truncated);
        assert!(output.log_backpressured);
    }

    #[test]
    fn public_node_crate_does_not_require_hosted_private_types() {
        let _tenant = TenantId::from("tenant");
        let _project = ProjectId::from("project");
        let _backend = LinuxRootlessPodmanBackend;
    }
}