from __future__ import annotations
import asyncio
import uuid
from dataclasses import dataclass, field
from datetime import datetime, timezone
from typing import Optional

from .config import Settings
from .models import Catalog, build_launch_command
from .ssh import ssh_run, ssh_stream, StreamHandle


READY_MARKER = "Application startup complete."
MAX_LINES = 500


@dataclass
class SwapJob:
    id: str
    model_key: str
    started_at: str
    state: str = "starting"   # starting|stopping|launching|tailing|ready|failed
    lines: list[str] = field(default_factory=list)
    returncode: Optional[int] = None
    finished_at: Optional[str] = None
    dry_run: bool = False

    def append(self, line: str) -> None:
        self.lines.append(line)
        if len(self.lines) > MAX_LINES:
            del self.lines[: len(self.lines) - MAX_LINES]


class SwapManager:
    def __init__(self, settings: Settings, catalog: Catalog) -> None:
        self.settings = settings
        self.catalog = catalog
        self.lock = asyncio.Lock()
        self.jobs: dict[str, SwapJob] = {}
        self.current_job_id: Optional[str] = None

    def get(self, job_id: str) -> SwapJob | None:
        return self.jobs.get(job_id)

    def reload_catalog(self, catalog: Catalog) -> None:
        self.catalog = catalog

    async def trigger(self, model_key: str, *, dry_run: bool = False) -> SwapJob:
        if model_key not in self.catalog.models:
            raise KeyError(model_key)
        if self.lock.locked():
            raise RuntimeError("A swap is already in progress")
        job = SwapJob(
            id=uuid.uuid4().hex[:8],
            model_key=model_key,
            started_at=datetime.now(timezone.utc).isoformat(),
            dry_run=dry_run,
        )
        self.jobs[job.id] = job
        self.current_job_id = job.id
        asyncio.create_task(self._run(job))
        return job

    async def _run(self, job: SwapJob) -> None:
        async with self.lock:
            try:
                await self._do(job)
                if job.state != "failed":
                    job.state = "ready"
                    job.returncode = 0
            except Exception as e:
                job.append(f"[error] {type(e).__name__}: {e}")
                job.state = "failed"
                if job.returncode is None:
                    job.returncode = 1
            finally:
                job.finished_at = datetime.now(timezone.utc).isoformat()
                if self.current_job_id == job.id:
                    self.current_job_id = None

    async def _do(self, job: SwapJob) -> None:
        model = self.catalog.models[job.model_key]
        s = self.settings

        # Step 1: stop
        job.state = "stopping"
        stop_cmd = "cd ~/spark-vllm-docker && ./launch-cluster.sh stop"
        job.append(f"$ {stop_cmd}")
        if not job.dry_run:
            rc, out, err = await ssh_run(s.spark1_host, s.spark1_user, stop_cmd, s, timeout=180)
            for line in (out + err).splitlines():
                job.append(line)
            if rc != 0:
                job.returncode = rc
                job.state = "failed"
                return

        # Step 2: launch
        job.state = "launching"
        launch = build_launch_command(job.model_key, model, self.catalog.defaults)
        launch_cmd = f"cd ~/spark-vllm-docker && {launch}"
        job.append(f"$ {launch_cmd}")
        if job.dry_run:
            return
        rc, out, err = await ssh_run(s.spark1_host, s.spark1_user, launch_cmd, s, timeout=60)
        for line in (out + err).splitlines():
            job.append(line)
        if rc != 0:
            job.returncode = rc
            job.state = "failed"
            return

        # Step 3: tail logs until the ready marker (or timeout)
        job.state = "tailing"
        tail_cmd = "docker logs -f --tail 50 vllm_node"
        job.append(f"$ {tail_cmd}")
        timeout = max(model.expected_ready_seconds * 2, 600)
        handle = StreamHandle()
        loop = asyncio.get_event_loop()
        deadline = loop.time() + timeout
        ready = False

        async def _tail() -> bool:
            async for line in ssh_stream(s.spark1_host, s.spark1_user, tail_cmd, s, handle=handle):
                job.append(line)
                if READY_MARKER in line:
                    return True
                if loop.time() > deadline:
                    return False
            return False

        try:
            ready = await asyncio.wait_for(_tail(), timeout=timeout + 30)
        except asyncio.TimeoutError:
            ready = False

        if not ready:
            job.append(f"[error] did not see '{READY_MARKER}' within {timeout}s")
            job.state = "failed"
            job.returncode = 124