import asyncio
import time
from pathlib import Path

from app.db import SessionLocal
from app.models import JobRun
from app.settings import settings

# Single global lock replacing /var/lock/sldl-pipeline.lock + flock -n. One
# process (this one) now owns every pipeline invocation, so one asyncio.Lock
# is enough -- deliberately not per-resource, matching the original flock's
# all-jobs-share-one-lock behavior exactly rather than over-engineering it.
_lock = asyncio.Lock()

_ENV_PASSTHROUGH_KEYS = ("PATH", "HOME", "LANG", "LC_ALL", "TZ")


async def _try_acquire_nowait() -> bool:
    """asyncio.Lock has no acquire_nowait(). asyncio.wait_for(lock.acquire(),
    timeout=0) looks like the obvious idiom but is broken in practice: it
    wraps acquire() in a Task, and the Task's first iteration and the
    timeout-0 callback are both scheduled via the event loop with no
    guaranteed ordering, so it times out almost every time even when the
    lock is completely uncontended (confirmed empirically -- the very first,
    uncontended call failed every time). The correct pattern relies on
    Lock.acquire()'s fast path never suspending when the lock is free: the
    .locked() check and the subsequent acquire() happen with no `await`
    point in between, so nothing else can interleave in this single-
    threaded event loop."""
    if _lock.locked():
        return False
    await _lock.acquire()
    return True


def _subprocess_env() -> dict:
    import os

    env = {k: v for k, v in os.environ.items() if k in _ENV_PASSTHROUGH_KEYS}
    env.setdefault("PATH", "/opt/venv/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin")
    env["ALEMBIC_CONFIG_DIR"] = str(settings.alembic_config_dir)
    env["MUSIC_DATA_DIR"] = str(settings.music_data_dir)
    env["PIPELINE_DIR"] = str(settings.pipeline_dir)
    env["BEETSDIR"] = str(settings.beets_dir)
    return env


def _summarize_log(log_path: Path, max_len: int = 200) -> str:
    """Best-effort one-liner for the jobs list: the log's last non-empty
    line. Scripts here already end their own runs with a human-readable
    '=== ... done ===' / summary line (see pipeline-status.sh's convention),
    so this is usually meaningful without any per-script special-casing."""
    try:
        lines = [line for line in log_path.read_text(errors="replace").splitlines() if line.strip()]
        return lines[-1][:max_len] if lines else ""
    except OSError:
        return ""


async def run_job(
    job_key: str,
    argv: list[str],
    triggered_by: str = "schedule",
    timeout: float | None = None,
) -> JobRun:
    """Run a pipeline command under the shared mutual-exclusion lock,
    recording one job_runs row start-to-finish. If the lock is already
    held, records status='skipped_lock' immediately and returns without
    running anything -- the old flock -n behavior, now visible in the UI
    instead of silently skipping."""
    started_at = time.time()

    if not await _try_acquire_nowait():
        db = SessionLocal()
        run = JobRun(
            job_key=job_key,
            started_at=started_at,
            finished_at=started_at,
            status="skipped_lock",
            triggered_by=triggered_by,
        )
        db.add(run)
        db.commit()
        db.refresh(run)
        db.close()
        return run

    try:
        log_dir = settings.logs_dir / job_key.replace(":", "_")
        log_dir.mkdir(parents=True, exist_ok=True)
        log_path = log_dir / f"{time.strftime('%Y%m%d-%H%M%S')}.log"

        db = SessionLocal()
        run = JobRun(
            job_key=job_key,
            started_at=started_at,
            status="running",
            triggered_by=triggered_by,
            log_path=str(log_path),
        )
        db.add(run)
        db.commit()
        db.refresh(run)
        run_id = run.id
        db.close()

        exit_code: int | None
        try:
            with open(log_path, "wb") as log_file:
                proc = await asyncio.create_subprocess_exec(
                    *argv,
                    stdout=log_file,
                    stderr=asyncio.subprocess.STDOUT,
                    env=_subprocess_env(),
                )
                try:
                    exit_code = await asyncio.wait_for(proc.wait(), timeout=timeout)
                except asyncio.TimeoutError:
                    proc.kill()
                    await proc.wait()
                    exit_code = -1
                    with open(log_path, "a") as f:
                        f.write(f"\n[pipeline_runner] TIMEOUT after {timeout}s -- process killed\n")
            status = "success" if exit_code == 0 else "failed"
        except Exception as exc:
            exit_code = None
            status = "failed"
            with open(log_path, "a") as f:
                f.write(f"\n[pipeline_runner] exception before/while running: {exc!r}\n")

        finished_at = time.time()
        db = SessionLocal()
        run = db.get(JobRun, run_id)
        run.finished_at = finished_at
        run.status = status
        run.exit_code = exit_code
        run.summary = _summarize_log(log_path)
        db.commit()
        db.refresh(run)
        db.close()
        return run
    finally:
        _lock.release()


async def run_playlist(playlist_name: str, no_m3u: bool = False, triggered_by: str = "schedule") -> JobRun:
    script = settings.pipeline_dir / "bin" / "run-playlist.sh"
    argv = [str(script)]
    if no_m3u:
        argv.append("--no-m3u")
    argv.append(playlist_name)
    # 45 min SLDL_TIMEOUT (run-playlist.sh) + generous slack for the
    # tagging/beets-import/M3U steps that follow it in the same script.
    return await run_job(f"playlist:{playlist_name}", argv, triggered_by=triggered_by, timeout=3300)


async def run_import_track(args: list[str], triggered_by: str = "manual") -> JobRun:
    script = settings.pipeline_dir / "bin" / "import-track.sh"
    return await run_job("manual:import", [str(script)] + args, triggered_by=triggered_by)


async def run_lib_script(job_key: str, script_name: str, args: list[str] | None = None, triggered_by: str = "schedule") -> JobRun:
    script = settings.pipeline_dir / "lib" / script_name
    return await run_job(job_key, [str(script)] + (args or []), triggered_by=triggered_by)


async def run_beet(job_key: str, args: list[str], triggered_by: str = "schedule") -> JobRun:
    return await run_job(job_key, ["beet"] + args, triggered_by=triggered_by)