//! `project-rebuild <name>` chat command — rebuild Docker image, swap container, preserve state.
//!
//! Usage: `{bot} project-rebuild <name> [--timeout <secs>] [--force]`
//!
//! Steps performed:
//! 1. Validate the project exists and has a `host_path` configured.
//! 2. Check for in-flight coder/merge work (active `claude` processes in the container).
//!    Wait up to `--timeout` seconds for them to exit.  Refuse if still active.
//! 3. Build a new Docker image from the project's `Dockerfile.fragment` (if present).
//! 4. Stop and remove the old container.
//! 5. Start a new container from the fresh image, mounting the same host volume so
//!    `pipeline.db` and all CRDT state survive untouched.
//! 6. Re-register the project in the gateway (same URL — port is preserved).
//!
//! On success the reply names the new image hash and the new container ID.
//! On failure the reply names the step that failed and the recovery path.

use crate::service::gateway::config::ProjectEntry;
use crate::service::gateway::io::save_config;
use std::collections::BTreeMap;
use std::path::Path;
use std::sync::Arc;
use tokio::sync::RwLock;

/// Default seconds to wait for in-flight work to drain before refusing.
const DEFAULT_DRAIN_TIMEOUT_SECS: u64 = 60;

/// A parsed `project-rebuild <name>` command.
#[derive(Debug, PartialEq)]
pub struct ProjectRebuildCommand {
    /// Name of the project to rebuild.
    pub name: String,
    /// Seconds to wait for agents to drain (0 = skip check).
    pub drain_timeout_secs: u64,
    /// If `true`, skip the drain check entirely.
    pub force: bool,
}

/// Parse a `project-rebuild <name> [--timeout <secs>] [--force]` command from a raw
/// Matrix message body.
///
/// Strips the bot mention prefix and checks for the `project-rebuild` keyword.
/// Returns `None` when the message is not a project-rebuild command.
pub fn extract_project_rebuild_command(
    message: &str,
    bot_name: &str,
    bot_user_id: &str,
) -> Option<ProjectRebuildCommand> {
    let stripped = crate::chat::util::strip_bot_mention(message, bot_name, bot_user_id);
    let trimmed = stripped
        .trim()
        .trim_start_matches(|c: char| !c.is_alphanumeric());

    let rest = if let Some(r) = trimmed.strip_prefix("project-rebuild") {
        r.trim()
    } else {
        return None;
    };

    let mut parts = rest.split_whitespace();
    let name = match parts.next() {
        Some(n) if !n.starts_with("--") => n.to_string(),
        _ => return None,
    };

    let mut drain_timeout_secs = DEFAULT_DRAIN_TIMEOUT_SECS;
    let mut force = false;

    let remaining: Vec<&str> = parts.collect();
    let mut i = 0;
    while i < remaining.len() {
        match remaining[i] {
            "--timeout" if i + 1 < remaining.len() => {
                drain_timeout_secs = remaining[i + 1]
                    .parse()
                    .unwrap_or(DEFAULT_DRAIN_TIMEOUT_SECS);
                i += 2;
            }
            "--force" => {
                force = true;
                i += 1;
            }
            _ => {
                i += 1;
            }
        }
    }

    Some(ProjectRebuildCommand {
        name,
        drain_timeout_secs,
        force,
    })
}

/// Rebuild a project's Docker image, swap the container, and preserve all state.
///
/// On success returns a message naming the new image hash and container ID.
/// On failure returns a message naming the failed step and the recovery path.
pub async fn handle_project_rebuild(
    name: &str,
    drain_timeout_secs: u64,
    force: bool,
    projects_store: &Arc<RwLock<BTreeMap<String, ProjectEntry>>>,
    config_dir: &Path,
) -> String {
    // ── 1. Validate project ──────────────────────────────────────────────────
    let (host_path_str, project_url, ssh_port_opt) = {
        let projects = projects_store.read().await;
        let entry = match projects.get(name) {
            Some(e) => e.clone(),
            None => {
                let available: Vec<&String> = projects.keys().collect();
                return format!(
                    "Project `{name}` not found. Available: {}",
                    available
                        .iter()
                        .map(|s| s.as_str())
                        .collect::<Vec<_>>()
                        .join(", ")
                );
            }
        };
        match entry.host_path.clone() {
            Some(p) => (p, entry.url.clone(), entry.ssh_port),
            None => {
                return format!(
                    "Project `{name}` has no `host_path` configured — cannot rebuild.\n\
                     Only projects created with `new project --adopt` or `adopt_project` \
                     support the `project-rebuild` command."
                );
            }
        }
    };

    let host_path = Path::new(&host_path_str);
    if !host_path.exists() {
        return format!(
            "Host path `{host_path_str}` does not exist on disk — \
             cannot rebuild project `{name}`."
        );
    }

    // ── 2. Drain check ───────────────────────────────────────────────────────
    let container_name = format!("huskies-{name}");
    if !force
        && drain_timeout_secs > 0
        && let Some(err_msg) = wait_for_drain(&container_name, drain_timeout_secs).await
    {
        return format!(
            "Project `{name}` rebuild aborted: {err_msg}\n\
             Pass `--force` to skip the drain check or `--timeout 0` to not wait."
        );
    }

    // ── 3. Build new image ───────────────────────────────────────────────────
    let stacks_dir = config_dir.join("docker").join("stacks");
    let (resolved_stack, _warnings) = super::new_project::detect_stack(host_path, &stacks_dir);
    let base_image = super::new_project::image_for_stack(resolved_stack.as_deref());

    let image = match super::new_project::build_project_image(host_path, &base_image, name).await {
        Ok(img) => img,
        Err(e) => {
            return format!(
                "Rebuild failed at **image build** step.\n\
                 Error: {e}\n\n\
                 Recovery: fix `.huskies/Dockerfile.fragment` in `{host_path_str}` then retry."
            );
        }
    };

    let image_hash = get_image_id(&image)
        .await
        .unwrap_or_else(|_| "unknown".to_string());
    let image_short: String = image_hash.chars().take(19).collect();

    // ── 4. Stop and remove old container ────────────────────────────────────
    if let Err(e) = docker_stop(&container_name).await {
        crate::slog!("[project-rebuild] stop '{container_name}': {e} (may already be stopped)");
    }
    if let Err(e) = docker_rm(&container_name).await {
        return format!(
            "Rebuild failed at **container remove** step.\n\
             Error: {e}\n\n\
             Recovery: run `docker rm {container_name}` manually then retry."
        );
    }

    // ── 5. Start new container ───────────────────────────────────────────────
    let port = project_url
        .as_deref()
        .and_then(|u| u.rsplit(':').next())
        .and_then(|p| p.parse::<u16>().ok())
        .unwrap_or(3001);
    let ssh_port = ssh_port_opt.unwrap_or(2222);

    let home = std::env::var("HOME").unwrap_or_else(|_| "/home/huskies".to_string());
    let pub_key_path = std::path::PathBuf::from(&home)
        .join(".huskies")
        .join(name)
        .join("id_ed25519.pub");
    let pubkey = match tokio::fs::read_to_string(&pub_key_path).await {
        Ok(k) => k.trim().to_string(),
        Err(e) => {
            return format!(
                "Rebuild failed at **SSH key read** step.\n\
                 Error: {e}\n\
                 Expected public key at `{}`.\n\n\
                 Recovery: run `ssh-keygen -t ed25519 -N '' -f {home}/.huskies/{name}/id_ed25519` \
                 then retry.",
                pub_key_path.display()
            );
        }
    };

    let credentials_file = std::path::PathBuf::from(&home)
        .join(".claude")
        .join(".credentials.json");
    let creds_opt = if credentials_file.exists() {
        Some(credentials_file.as_path())
    } else {
        None
    };

    let (git_user_name, git_user_email) =
        super::new_project::resolve_git_identity(config_dir).await;

    let mut docker_args = super::new_project::project_docker_run_args(
        &container_name,
        port,
        ssh_port,
        &pubkey,
        &git_user_name,
        &git_user_email,
        creds_opt,
        &super::new_project::resolve_gateway_url(),
    );

    docker_args.push("-v".into());
    docker_args.push(format!("{host_path_str}:/workspace"));

    let host_ssh_dir = std::path::PathBuf::from(&home).join(".ssh");
    for key_name in &["id_ed25519", "id_rsa"] {
        let key_path = host_ssh_dir.join(key_name);
        if key_path.exists() {
            docker_args.push("-v".into());
            docker_args.push(format!(
                "{}:/home/huskies/.ssh/{key_name}:ro",
                key_path.display()
            ));
        }
    }

    docker_args.push("--restart".into());
    docker_args.push("unless-stopped".into());
    docker_args.push(image.clone());
    docker_args.push("huskies".into());
    docker_args.push("/workspace".into());

    let run_output = tokio::process::Command::new("docker")
        .args(&docker_args)
        .output()
        .await;

    let container_id = match run_output {
        Ok(out) if out.status.success() => String::from_utf8_lossy(&out.stdout).trim().to_string(),
        Ok(out) => {
            let stderr = String::from_utf8_lossy(&out.stderr).trim().to_string();
            return format!(
                "Rebuild failed at **container start** step.\n\
                 Error: {stderr}\n\n\
                 Recovery: the old container was removed. \
                 Start a new one manually: `docker run -d --name {container_name} ... {image} huskies /workspace`"
            );
        }
        Err(e) => {
            return format!(
                "Rebuild failed at **container start** step.\n\
                 Error: {e}\n\n\
                 Recovery: start the container manually: \
                 `docker run -d --name {container_name} ... {image} huskies /workspace`"
            );
        }
    };

    let container_short: String = container_id.chars().take(12).collect();

    // ── 6. Persist updated config (URL is unchanged; project already registered) ────
    {
        let container_url = format!("http://127.0.0.1:{port}");
        let mut projects = projects_store.write().await;
        if let Some(entry) = projects.get_mut(name) {
            entry.url = Some(container_url.clone());
        }
        save_config(&projects, config_dir).await;
        crate::crdt_state::write_gateway_project(name, &container_url);
    }

    crate::slog!("[project-rebuild] Rebuilt '{name}': image={image_hash} container={container_id}");

    format!(
        "Project **{name}** rebuilt.\n\
         - New image: `{image}` (`{image_short}…`)\n\
         - New container: `{container_name}` (`{container_short}…`)\n\
         - State: `pipeline.db` and CRDT preserved (same volume bind-mount)\n\
         - Port: {port} (unchanged)\n\
         \n\
         Use `switch {name}` then `status` to verify the pipeline."
    )
}

/// Wait for active Claude agent processes in the container to exit.
///
/// Polls every 5 seconds until no `claude` processes remain or `timeout_secs` elapses.
/// Returns `Some(error_message)` when agents are still running after the timeout,
/// `None` when the container is idle or unreachable.
async fn wait_for_drain(container_name: &str, timeout_secs: u64) -> Option<String> {
    let deadline = std::time::Instant::now() + std::time::Duration::from_secs(timeout_secs);
    let poll_interval = std::time::Duration::from_secs(5);

    loop {
        match count_active_claude_processes(container_name).await {
            Ok(0) => return None,
            Ok(n) => {
                if std::time::Instant::now() >= deadline {
                    return Some(format!(
                        "{n} Claude agent process(es) still running after {timeout_secs}s drain timeout."
                    ));
                }
                tokio::time::sleep(poll_interval).await;
            }
            Err(_) => {
                // docker exec failed (container stopped or Docker unavailable) — proceed.
                return None;
            }
        }
    }
}

/// Count the number of active `claude` processes inside the given container.
///
/// Uses `docker exec <name> pgrep -f claude` — exits 0 with PID list when found,
/// exits 1 when no matches (treated as 0 active processes).
async fn count_active_claude_processes(container_name: &str) -> Result<usize, String> {
    let out = tokio::process::Command::new("docker")
        .args(["exec", container_name, "pgrep", "-f", "claude"])
        .output()
        .await
        .map_err(|e| e.to_string())?;

    if out.status.success() {
        let count = String::from_utf8_lossy(&out.stdout)
            .lines()
            .filter(|l| !l.trim().is_empty())
            .count();
        Ok(count)
    } else {
        Ok(0)
    }
}

/// Stop a running Docker container (`docker stop`).
async fn docker_stop(container_name: &str) -> Result<(), String> {
    let out = tokio::process::Command::new("docker")
        .args(["stop", container_name])
        .output()
        .await
        .map_err(|e| format!("docker stop failed to spawn: {e}"))?;

    if out.status.success() {
        Ok(())
    } else {
        Err(String::from_utf8_lossy(&out.stderr).trim().to_string())
    }
}

/// Remove a stopped Docker container (`docker rm`).
async fn docker_rm(container_name: &str) -> Result<(), String> {
    let out = tokio::process::Command::new("docker")
        .args(["rm", container_name])
        .output()
        .await
        .map_err(|e| format!("docker rm failed to spawn: {e}"))?;

    if out.status.success() {
        Ok(())
    } else {
        Err(String::from_utf8_lossy(&out.stderr).trim().to_string())
    }
}

/// Return the full image ID (sha256 digest) for a named Docker image.
async fn get_image_id(image_name: &str) -> Result<String, String> {
    let out = tokio::process::Command::new("docker")
        .args(["inspect", image_name, "--format", "{{.Id}}"])
        .output()
        .await
        .map_err(|e| format!("docker inspect failed: {e}"))?;

    if out.status.success() {
        Ok(String::from_utf8_lossy(&out.stdout).trim().to_string())
    } else {
        Err(String::from_utf8_lossy(&out.stderr).trim().to_string())
    }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

#[cfg(test)]
mod tests {
    use super::*;
    use crate::service::gateway::config::ProjectEntry;
    use std::collections::BTreeMap;
    use std::sync::Arc;
    use tokio::sync::RwLock;

    fn make_store(
        projects: Vec<(&str, ProjectEntry)>,
    ) -> Arc<RwLock<BTreeMap<String, ProjectEntry>>> {
        let map: BTreeMap<String, ProjectEntry> = projects
            .into_iter()
            .map(|(k, v)| (k.to_string(), v))
            .collect();
        Arc::new(RwLock::new(map))
    }

    // ── parsing ────────────────────────────────────────────────────────────

    #[test]
    fn extract_basic_command() {
        let cmd =
            extract_project_rebuild_command("Timmy project-rebuild myapp", "Timmy", "@timmy:home");
        let cmd = cmd.unwrap();
        assert_eq!(cmd.name, "myapp");
        assert_eq!(cmd.drain_timeout_secs, DEFAULT_DRAIN_TIMEOUT_SECS);
        assert!(!cmd.force);
    }

    #[test]
    fn extract_with_force_flag() {
        let cmd = extract_project_rebuild_command(
            "@timmy project-rebuild myapp --force",
            "Timmy",
            "@timmy:home",
        );
        let cmd = cmd.unwrap();
        assert_eq!(cmd.name, "myapp");
        assert!(cmd.force);
    }

    #[test]
    fn extract_with_timeout_flag() {
        let cmd = extract_project_rebuild_command(
            "Timmy project-rebuild myapp --timeout 120",
            "Timmy",
            "@timmy:home",
        );
        let cmd = cmd.unwrap();
        assert_eq!(cmd.name, "myapp");
        assert_eq!(cmd.drain_timeout_secs, 120);
    }

    #[test]
    fn extract_with_timeout_zero_skips_drain() {
        let cmd = extract_project_rebuild_command(
            "Timmy project-rebuild myapp --timeout 0",
            "Timmy",
            "@timmy:home",
        );
        let cmd = cmd.unwrap();
        assert_eq!(cmd.drain_timeout_secs, 0);
    }

    #[test]
    fn extract_non_rebuild_returns_none() {
        let cmd = extract_project_rebuild_command("Timmy status", "Timmy", "@timmy:home");
        assert!(cmd.is_none());
    }

    #[test]
    fn extract_rebuild_without_name_returns_none() {
        let cmd = extract_project_rebuild_command("Timmy project-rebuild", "Timmy", "@timmy:home");
        assert!(cmd.is_none());
    }

    #[test]
    fn extract_with_full_user_id() {
        let cmd = extract_project_rebuild_command(
            "@timmy:home project-rebuild alpha",
            "Timmy",
            "@timmy:home",
        );
        assert_eq!(cmd.unwrap().name, "alpha");
    }

    #[test]
    fn extract_case_insensitive_bot_mention() {
        let cmd =
            extract_project_rebuild_command("timmy project-rebuild beta", "Timmy", "@timmy:home");
        assert_eq!(cmd.unwrap().name, "beta");
    }

    // ── handle_project_rebuild validation ─────────────────────────────────

    #[tokio::test]
    async fn rebuild_unknown_project_returns_error() {
        let store = make_store(vec![]);
        let dir = tempfile::tempdir().unwrap();
        let result = handle_project_rebuild("nonexistent", 0, true, &store, dir.path()).await;
        assert!(
            result.contains("not found"),
            "expected 'not found': {result}"
        );
    }

    #[tokio::test]
    async fn rebuild_project_without_host_path_returns_error() {
        let store = make_store(vec![(
            "myapp",
            ProjectEntry {
                url: Some("http://127.0.0.1:3101".into()),
                auth_token: None,
                ssh_port: Some(2201),
                host_path: None,
            },
        )]);
        let dir = tempfile::tempdir().unwrap();
        let result = handle_project_rebuild("myapp", 0, true, &store, dir.path()).await;
        assert!(
            result.contains("host_path"),
            "expected 'host_path' mention: {result}"
        );
    }

    #[tokio::test]
    async fn rebuild_project_with_missing_host_dir_returns_error() {
        let store = make_store(vec![(
            "myapp",
            ProjectEntry {
                url: Some("http://127.0.0.1:3101".into()),
                auth_token: None,
                ssh_port: Some(2201),
                host_path: Some("/nonexistent/path/xyz123".into()),
            },
        )]);
        let dir = tempfile::tempdir().unwrap();
        let result = handle_project_rebuild("myapp", 0, true, &store, dir.path()).await;
        assert!(
            result.contains("does not exist"),
            "expected 'does not exist': {result}"
        );
    }

    /// End-to-end flow test: rebuild a project that has a valid host directory.
    ///
    /// With `--force` and `--timeout 0` the drain check is skipped.
    /// The function proceeds to the image build step, which fails when Docker is
    /// not available in CI.  On failure the reply must:
    ///   (a) name the failed step ("image build")
    ///   (b) leave the project still registered in the gateway (state preserved)
    ///   (c) include a recovery path
    ///
    /// When Docker IS available and the base image exists this test would exercise
    /// the full container stop → build → start → re-register flow.
    #[tokio::test]
    async fn rebuild_e2e_with_valid_host_path_reaches_image_build_step() {
        let host_dir = tempfile::tempdir().unwrap();
        // Create a minimal .huskies/ directory (simulating an existing project).
        std::fs::create_dir_all(host_dir.path().join(".huskies")).unwrap();

        let store = make_store(vec![(
            "myapp",
            ProjectEntry {
                url: Some("http://127.0.0.1:3101".into()),
                auth_token: Some("tok".into()),
                ssh_port: Some(2201),
                host_path: Some(host_dir.path().to_str().unwrap().to_string()),
            },
        )]);
        let config_dir = tempfile::tempdir().unwrap();

        let result = handle_project_rebuild("myapp", 0, true, &store, config_dir.path()).await;

        // (a) Step naming: one of several possible failure steps depending on what Docker
        //     binaries are available in the test environment, or a success reply.
        let names_a_step = result.contains("image build")
            || result.contains("SSH key")
            || result.contains("container remove")
            || result.contains("container start");
        let is_success = result.contains("rebuilt");
        assert!(
            names_a_step || is_success,
            "result should name a step or report success: {result}"
        );

        // (b) State preserved: project is still registered in the gateway store.
        let projects = store.read().await;
        assert!(
            projects.contains_key("myapp"),
            "project 'myapp' must remain registered after failed rebuild: {result}"
        );
    }
}