"""Persistent per-URL state: makes runs resumable and failures trackable.

state.json lives in the run's OUT_DIR and maps every URL seen to a record:

    {
      "status": "ok" | "failed" | "error",
      "attempts": <int>,
      "error": "<last error message>",
      "files": [{"path": ..., "size": ...}, ...],
      "updated": "<iso timestamp>"
    }

Re-running skips URLs whose status is "ok"; failed URLs are retried and also
written to failed_urls.txt for easy manual retry lists.
"""

from __future__ import annotations

import json
import logging
import time
from pathlib import Path

log = logging.getLogger(__name__)


class State:
    """JSON-backed state store for one run directory."""

    def __init__(self, path: Path):
        self.path = path
        self.records: dict[str, dict] = {}
        if path.exists():
            try:
                self.records = json.loads(path.read_text(encoding="utf-8"))
                if not isinstance(self.records, dict):
                    raise ValueError("state root must be an object")
            except (ValueError, OSError) as exc:
                backup = path.with_suffix(".json.bak")
                log.warning("Corrupt state file %s (%s); moving to %s and starting fresh",
                            path, exc, backup)
                path.replace(backup)
                self.records = {}

    def is_done(self, url: str) -> bool:
        rec = self.records.get(url)
        return bool(rec) and rec.get("status") == "ok"

    def pending(self, urls: list[str]) -> list[str]:
        return [u for u in urls if not self.is_done(u)]

    def mark(self, url: str, **fields) -> dict:
        rec = self.records.setdefault(url, {"status": "pending", "attempts": 0, "files": []})
        for key, value in fields.items():
            if value is not None:
                rec[key] = value
        rec["attempts"] = rec.get("attempts", 0) + 1
        rec["updated"] = time.strftime("%Y-%m-%dT%H:%M:%S")
        self.save()
        return rec

    def failures(self) -> list[str]:
        return [u for u, r in self.records.items() if r.get("status") != "ok"]

    def save(self) -> None:
        self.path.parent.mkdir(parents=True, exist_ok=True)
        tmp = self.path.with_suffix(".json.tmp")
        tmp.write_text(
            json.dumps(self.records, indent=2, sort_keys=True), encoding="utf-8"
        )
        tmp.replace(self.path)


def append_manifest(manifest_path: Path, row: dict) -> None:
    """Append one JSON line to manifest.jsonl (per downloaded file)."""
    manifest_path.parent.mkdir(parents=True, exist_ok=True)
    with manifest_path.open("a", encoding="utf-8") as fh:
        fh.write(json.dumps(row, ensure_ascii=False) + "\n")