"""JSON state store under state/: one file for all projects, an exclusive tick lock, heartbeat and log.

state/agentd-state.json:
  {"projects": {PROJECT: {"issues": {issue_uuid: rec}}}, "paused_groups": {group: {...}}}
rec: seq, runs, thread_id, thread_on [terminal, executor], thread_rounds, tags [...], last_message,
     seen_comments [...], last_comment_at, retries, retry {at, reason}, rebuild, inflight {...}"""
import contextlib
import fcntl
import json
import os
import time
from pathlib import Path


class Busy(Exception):
    pass


class Store:
    def __init__(self, state_dir, echo=True):
        self.dir = Path(state_dir)
        self.echo = echo
        self.path = self.dir / "agentd-state.json"

    def load(self):
        if self.path.exists():
            data = json.loads(self.path.read_text(encoding="utf-8"))
        else:
            data = {}
        data.setdefault("projects", {})
        data.setdefault("paused_groups", {})
        return data

    def _atomic_write(self, path, obj):
        """Write temp + fsync + rename, so a reader (or a crash) never sees half a file."""
        self.dir.mkdir(parents=True, exist_ok=True)
        tmp = path.with_suffix(".tmp")
        with open(tmp, "w", encoding="utf-8") as fh:
            fh.write(json.dumps(obj, ensure_ascii=False, indent=1))
            fh.flush()
            os.fsync(fh.fileno())
        os.replace(tmp, path)

    def save(self, data):
        self._atomic_write(self.path, data)

    @contextlib.contextmanager
    def lock(self):
        self.dir.mkdir(parents=True, exist_ok=True)
        with open(self.dir / "agentd.lock", "w") as fh:
            try:
                fcntl.flock(fh, fcntl.LOCK_EX | fcntl.LOCK_NB)
            except BlockingIOError:
                raise Busy("another tick holds %s" % (self.dir / "agentd.lock")) from None
            yield

    def heartbeat(self, info):
        info = dict(info, ts=time.time(), at=time.strftime("%Y-%m-%dT%H:%M:%S"))
        self._atomic_write(self.dir / "heartbeat.json", info)

    def log(self, msg):
        self.dir.mkdir(parents=True, exist_ok=True)
        line = time.strftime("%Y-%m-%dT%H:%M:%S") + " " + msg
        if self.echo:
            print(line, flush=True)
        with open(self.dir / "agentd.log", "a", encoding="utf-8") as fh:
            fh.write(line + "\n")