mxsh 0.1.0

use std::collections::{HashMap, VecDeque};
use std::io;
use std::path::{Path, PathBuf};
use std::sync::Arc;
use std::thread::JoinHandle;

use super::*;

/// Type alias for in-memory command implementations.
pub type InMemoryCommand =
    Arc<dyn Fn(&[String], &[(String, String)], &Path, SpawnStdio) -> i32 + Send + Sync>;

/// In-memory implementation of the runtime trait for testing.
///
/// External commands are dispatched to registered closures.
pub struct InMemoryRuntime {
    commands: HashMap<String, InMemoryCommand>,
    next_job_id: u32,
    pending: HashMap<u32, JoinHandle<i32>>,
}

impl Clone for InMemoryRuntime {
    fn clone(&self) -> Self {
        Self {
            commands: self.commands.clone(),
            next_job_id: self.next_job_id,
            pending: HashMap::new(),
        }
    }
}

impl std::fmt::Debug for InMemoryRuntime {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("InMemoryRuntime")
            .field("commands_len", &self.commands.len())
            .finish()
    }
}

impl InMemoryRuntime {
    /// Create a new InMemoryRuntime with no registered commands.
    pub fn new() -> Self {
        Self {
            commands: HashMap::new(),
            next_job_id: 1,
            pending: HashMap::new(),
        }
    }

    /// Register an in-memory command implementation.
    pub fn register_command<F>(&mut self, name: &str, command: F)
    where
        F: Fn(&[String], &[(String, String)], &Path, SpawnStdio) -> i32 + Send + Sync + 'static,
    {
        self.commands.insert(name.to_string(), Arc::new(command));
    }
}

impl Default for InMemoryRuntime {
    fn default() -> Self {
        Self::new()
    }
}

impl Runtime for InMemoryRuntime {
    type ForegroundGuard = ();

    fn fork(&self) -> Result<Self, io::Error> {
        Ok(Self {
            commands: self.commands.clone(),
            next_job_id: self.next_job_id,
            pending: HashMap::new(),
        })
    }

    fn spawn_external_command(
        &mut self,
        command: &ExternalCommand,
        stdio: SpawnStdio,
        _close_fds: &[FileDescriptor],
        _mode: SpawnMode,
    ) -> Result<SpawnedProcess, io::Error> {
        fn dup_stage_fd(fd: FileDescriptor) -> (FileDescriptor, bool) {
            if !fd.is_valid() {
                return (fd, false);
            }
            match fd.dup() {
                Ok(dup) => (dup, true),
                Err(_) => (fd, false),
            }
        }

        let argv = command.argv.clone();
        let env = command.env.clone();
        let cwd = command.cwd.clone();
        let (stdin_fd, close_stdin) = dup_stage_fd(stdio.stdin_fd);
        let (stdout_fd, close_stdout) = dup_stage_fd(stdio.stdout_fd);
        let (stderr_fd, close_stderr) = dup_stage_fd(stdio.stderr_fd);
        let stage_stdio = SpawnStdio {
            stdin_fd,
            stdout_fd,
            stderr_fd,
        };
        let maybe_cmd = argv
            .first()
            .and_then(|program| self.commands.get(program))
            .cloned();
        let handle = std::thread::spawn(move || {
            let status = match maybe_cmd {
                Some(cmd) => cmd(&argv, &env, &cwd, stage_stdio),
                None => 127,
            };
            if close_stdin {
                stdin_fd.close();
            }
            if close_stdout {
                stdout_fd.close();
            }
            if close_stderr {
                stderr_fd.close();
            }
            status
        });
        let child = self.next_job_id;
        self.next_job_id += 1;
        self.pending.insert(child, handle);
        Ok(SpawnedProcess {
            handle: ProcessHandle::new(child as u64),
            display_pid: Some(child),
        })
    }

    fn wait_process(
        &mut self,
        process: ProcessHandle,
        mode: WaitMode,
    ) -> Result<ProcessEvent, io::Error> {
        let child = process.as_u64() as u32;
        match mode {
            WaitMode::Poll => {
                let Some(handle) = self.pending.get(&child) else {
                    return Ok(ProcessEvent::Exited(0));
                };
                if !handle.is_finished() {
                    return Ok(ProcessEvent::Running);
                }
                let handle = self
                    .pending
                    .remove(&child)
                    .expect("pending handle should exist");
                Ok(ProcessEvent::Exited(handle.join().unwrap_or(128)))
            }
            WaitMode::Block => {
                let Some(handle) = self.pending.remove(&child) else {
                    return Ok(ProcessEvent::Exited(0));
                };
                Ok(ProcessEvent::Exited(handle.join().unwrap_or(128)))
            }
        }
    }

    fn wait_display_pid(&mut self, display_pid: u32) -> Result<Option<i32>, io::Error> {
        if !self.pending.contains_key(&display_pid) {
            return Err(io::Error::new(
                io::ErrorKind::NotFound,
                "unknown in-memory display pid",
            ));
        }
        Ok(Some(
            self.wait_child(ProcessHandle::new(display_pid as u64)),
        ))
    }

    fn signal_process_group(
        &mut self,
        _process: ProcessHandle,
        _signal: RuntimeSignal,
    ) -> Result<(), io::Error> {
        Ok(())
    }

    fn claim_foreground(
        &mut self,
        _process: ProcessHandle,
        _tty: FileDescriptor,
    ) -> Result<Self::ForegroundGuard, io::Error> {
        Ok(())
    }

    fn release_foreground(&mut self, _guard: Self::ForegroundGuard) -> Result<(), io::Error> {
        Ok(())
    }

    fn has_command(&self, program: &str) -> bool {
        self.commands.contains_key(program)
    }

    fn resolve_command_path(&self, program: &str, path_var: &str) -> Result<PathBuf, io::Error> {
        if self.commands.contains_key(program) {
            return Ok(PathBuf::from(program));
        }
        super::resolve_command_path(program, path_var)
    }

    fn exec_replace(
        &self,
        _program: &str,
        _argv: &[String],
        _env: &[(String, String)],
        _cwd: &Path,
    ) -> Result<(), io::Error> {
        Err(io::Error::new(
            io::ErrorKind::Unsupported,
            "exec is unavailable in the in-memory runtime",
        ))
    }
}

#[derive(Clone, Debug)]
enum DeterministicSpawn {
    Spawn(DeterministicProcess),
    Fail {
        kind: io::ErrorKind,
        message: String,
    },
}

#[derive(Clone, Debug)]
struct DeterministicProcess {
    handle: ProcessHandle,
    display_pid: Option<u32>,
    poll_events: VecDeque<ProcessEvent>,
    block_events: VecDeque<ProcessEvent>,
    last_event: ProcessEvent,
}

impl DeterministicProcess {
    fn next_event(&mut self, mode: WaitMode) -> ProcessEvent {
        let next = match mode {
            WaitMode::Poll => self.poll_events.pop_front(),
            WaitMode::Block => self.block_events.pop_front(),
        };
        if let Some(event) = next {
            self.last_event = event;
            event
        } else {
            self.last_event
        }
    }

    fn is_terminal(&self) -> bool {
        matches!(
            self.last_event,
            ProcessEvent::Exited(_) | ProcessEvent::Signaled(_)
        )
    }
}

/// Deterministic runtime for testing job lifecycle and job-control behavior.
#[derive(Clone, Debug, Default)]
pub struct DeterministicRuntime {
    next_handle: u64,
    queued_spawns: VecDeque<DeterministicSpawn>,
    processes: HashMap<ProcessHandle, DeterministicProcess>,
    display_to_handle: HashMap<u32, ProcessHandle>,
    recorded_signals: Vec<(ProcessHandle, RuntimeSignal)>,
    foreground_claims: Vec<(ProcessHandle, FileDescriptor)>,
    foreground_releases: usize,
}

impl DeterministicRuntime {
    /// Create an empty deterministic runtime.
    pub fn new() -> Self {
        Self {
            next_handle: 1,
            queued_spawns: VecDeque::new(),
            processes: HashMap::new(),
            display_to_handle: HashMap::new(),
            recorded_signals: Vec::new(),
            foreground_claims: Vec::new(),
            foreground_releases: 0,
        }
    }

    /// Queue one successful spawn with the provided wait events.
    pub fn push_spawn(
        &mut self,
        display_pid: Option<u32>,
        poll_events: impl IntoIterator<Item = ProcessEvent>,
        block_events: impl IntoIterator<Item = ProcessEvent>,
    ) -> ProcessHandle {
        let handle = ProcessHandle::new(self.next_handle);
        self.next_handle += 1;
        let process = DeterministicProcess {
            handle,
            display_pid,
            poll_events: poll_events.into_iter().collect(),
            block_events: block_events.into_iter().collect(),
            last_event: ProcessEvent::Running,
        };
        self.queued_spawns
            .push_back(DeterministicSpawn::Spawn(process));
        handle
    }

    /// Queue one failed spawn.
    pub fn push_spawn_error(&mut self, kind: io::ErrorKind, message: impl Into<String>) {
        self.queued_spawns.push_back(DeterministicSpawn::Fail {
            kind,
            message: message.into(),
        });
    }

    /// Return the semantic signals recorded so far.
    pub fn recorded_signals(&self) -> &[(ProcessHandle, RuntimeSignal)] {
        &self.recorded_signals
    }

    /// Return the foreground claims recorded so far.
    pub fn foreground_claims(&self) -> &[(ProcessHandle, FileDescriptor)] {
        &self.foreground_claims
    }

    /// Return the number of foreground releases performed so far.
    pub fn foreground_releases(&self) -> usize {
        self.foreground_releases
    }
}

impl Runtime for DeterministicRuntime {
    type ForegroundGuard = (ProcessHandle, FileDescriptor);

    fn fork(&self) -> Result<Self, io::Error> {
        Ok(Self {
            next_handle: self.next_handle,
            queued_spawns: VecDeque::new(),
            processes: HashMap::new(),
            display_to_handle: HashMap::new(),
            recorded_signals: Vec::new(),
            foreground_claims: Vec::new(),
            foreground_releases: 0,
        })
    }

    fn spawn_external_command(
        &mut self,
        _command: &ExternalCommand,
        _stdio: SpawnStdio,
        _close_fds: &[FileDescriptor],
        _mode: SpawnMode,
    ) -> Result<SpawnedProcess, io::Error> {
        match self.queued_spawns.pop_front() {
            Some(DeterministicSpawn::Spawn(process)) => {
                let display_pid = process.display_pid;
                let handle = process.handle;
                if let Some(display_pid) = display_pid {
                    self.display_to_handle.insert(display_pid, handle);
                }
                self.processes.insert(handle, process);
                Ok(SpawnedProcess {
                    handle,
                    display_pid,
                })
            }
            Some(DeterministicSpawn::Fail { kind, message }) => Err(io::Error::new(kind, message)),
            None => Err(io::Error::new(
                io::ErrorKind::NotFound,
                "no queued deterministic spawn",
            )),
        }
    }

    fn wait_process(
        &mut self,
        process: ProcessHandle,
        mode: WaitMode,
    ) -> Result<ProcessEvent, io::Error> {
        let Some(proc_state) = self.processes.get_mut(&process) else {
            return Err(io::Error::new(
                io::ErrorKind::NotFound,
                "unknown deterministic process handle",
            ));
        };
        let event = proc_state.next_event(mode);
        let finished = proc_state.is_terminal();
        let finished_display_pid = proc_state.display_pid;
        if finished {
            if let Some(display_pid) = finished_display_pid {
                self.display_to_handle.remove(&display_pid);
            }
            self.processes.remove(&process);
        }
        Ok(event)
    }

    fn wait_display_pid(&mut self, display_pid: u32) -> Result<Option<i32>, io::Error> {
        let handle = *self.display_to_handle.get(&display_pid).ok_or_else(|| {
            io::Error::new(io::ErrorKind::NotFound, "unknown deterministic display pid")
        })?;
        Ok(Some(self.wait_child(handle)))
    }

    fn signal_process_group(
        &mut self,
        process: ProcessHandle,
        signal: RuntimeSignal,
    ) -> Result<(), io::Error> {
        self.recorded_signals.push((process, signal));
        Ok(())
    }

    fn claim_foreground(
        &mut self,
        process: ProcessHandle,
        tty: FileDescriptor,
    ) -> Result<Self::ForegroundGuard, io::Error> {
        self.foreground_claims.push((process, tty));
        Ok((process, tty))
    }

    fn release_foreground(&mut self, _guard: Self::ForegroundGuard) -> Result<(), io::Error> {
        self.foreground_releases += 1;
        Ok(())
    }

    fn resolve_command_path(&self, program: &str, _path_var: &str) -> Result<PathBuf, io::Error> {
        Ok(PathBuf::from(program))
    }

    fn exec_replace(
        &self,
        _program: &str,
        _argv: &[String],
        _env: &[(String, String)],
        _cwd: &Path,
    ) -> Result<(), io::Error> {
        Err(io::Error::new(
            io::ErrorKind::Unsupported,
            "exec is unavailable in the deterministic runtime",
        ))
    }
}