import hashlib
import json
import os
import re
import time
import uuid
from pathlib import Path

from .contracts import StageEvent

OUTPUTS = Path(os.environ.get("STUDIO_OUTPUTS", "outputs")).resolve()


def digest(path: Path) -> str:
    with path.open("rb") as stream:
        return hashlib.file_digest(stream, "sha256").hexdigest()


class Run:
    def __init__(self, request):
        self.path = OUTPUTS / uuid.uuid4().hex
        self.path.mkdir(parents=True)
        self.data = {"id": self.path.name, "request": request.model_dump(mode="json"),
                     "created": time.time(), "status": "running", "events": [],
                     "completed_stages": [], "skipped_stages": [], "next_stage": "reference"}
        # Avoid retaining the upload cache's private path in downloadable metadata.
        self.data["request"]["image"] = "input.png" if request.image else None
        self.save()

    @classmethod
    def load(cls, run_id):
        if not isinstance(run_id, str) or not re.fullmatch(r"[0-9a-f]{32}", run_id):
            raise ValueError("Invalid run ID; expected 32 lowercase hexadecimal characters.")
        path = OUTPUTS / run_id
        if path.is_symlink() or path.resolve().parent != OUTPUTS.resolve():
            raise ValueError("Run path is outside the output directory.")
        manifest = path / "manifest.json"
        if manifest.is_symlink():
            raise ValueError("Run manifest must not be a symlink.")
        data = json.loads(manifest.read_text())
        if not isinstance(data, dict) or data.get("id") != run_id:
            raise ValueError("Run manifest ID does not match its directory.")
        if data.get("request", {}).get("image") not in {None, "input.png"}:
            raise ValueError("Run request contains an invalid input path.")
        run = cls.__new__(cls)
        run.path, run.data = path, data
        return run

    def save(self):
        temporary = self.path / "manifest.tmp"
        temporary.write_text(json.dumps(self.data, indent=2))
        temporary.replace(self.path / "manifest.json")

    def event(self, stage, status, detail):
        self.data["events"].append(StageEvent(stage=stage, status=status, detail=detail).model_dump())
        self.save()

    def finish(self, status):
        self.data["status"] = status
        self.data["elapsed_seconds"] = round(time.time() - self.data["created"], 2)
        self.data["files"] = {str(p.relative_to(self.path)): digest(p)
                              for p in self.path.rglob("*") if p.is_file()
                              and p.name not in {"manifest.json", "asset.zip"}}
        self.save()