"""FastAPI backend for the local PR review dashboard.

Endpoints:
  GET  /                      -> serves the dashboard
  GET  /api/config            -> org/filter/model info for the UI
  GET  /api/prs               -> live list of PRs matching the filter
  GET  /api/reviews           -> cached, pre-computed reviews + per-PR status
  POST /api/refresh           -> ask the background worker to poll now (202)
  POST /api/review            -> run a Fireworks review for one PR on demand
  POST /api/revise            -> re-run review with the user's revision notes
  POST /api/post              -> submit the review to GitHub (side-effectful)

A background worker (app/worker.py) pre-reviews non-draft PRs into a SQLite cache
(app/store.py) so reviews are ready when opened. Nothing is ever posted
automatically. Single-user local tool.
"""

from __future__ import annotations

import hashlib
import json
from contextlib import asynccontextmanager
from pathlib import Path
from typing import Any

from fastapi import FastAPI, HTTPException
from fastapi.responses import FileResponse, JSONResponse
from fastapi.staticfiles import StaticFiles
from pydantic import BaseModel

from .config import get_config
from .github_client import GitHubClient, GitHubError
from .handbook import HandbookProvider
from .reviewer import Reviewer
from .store import ReviewStore
from .worker import Worker

cfg = get_config()

STATIC_DIR = Path(__file__).parent.parent / "static"

# lazy singletons so a missing token doesn't crash import
_gh: GitHubClient | None = None
_reviewer: Reviewer | None = None
_store: ReviewStore | None = None
_worker: Worker | None = None
_handbook: HandbookProvider | None = None


def gh() -> GitHubClient:
    global _gh
    if _gh is None:
        _gh = GitHubClient(cfg)
    return _gh


def reviewer() -> Reviewer:
    global _reviewer
    if _reviewer is None:
        _reviewer = Reviewer(cfg)
    return _reviewer


def store() -> ReviewStore | None:
    return _store


def worker() -> Worker | None:
    return _worker


def handbook() -> HandbookProvider | None:
    return _handbook


@asynccontextmanager
async def lifespan(app: FastAPI):
    # Initialize the singletons eagerly, before the worker thread starts, so the
    # worker and request handlers never race to lazily create them. The handbook
    # provider is built first, then the reviewer receives its digest callback
    # (set once at construction; no mutable setter, no circular reference).
    global _reviewer, _store, _worker, _handbook
    gh()
    _handbook = HandbookProvider(cfg)
    _reviewer = Reviewer(cfg, guidance_provider=_handbook.current_digest)
    _store = ReviewStore(cfg.CACHE_DB)
    _worker = Worker(cfg, _gh, _reviewer, _store, handbook=_handbook)
    _worker.start()
    try:
        yield
    finally:
        if _worker is not None:
            _worker.stop()


app = FastAPI(title="PR Review Dashboard", lifespan=lifespan)
app.mount("/static", StaticFiles(directory=STATIC_DIR), name="static")


@app.get("/")
def index() -> FileResponse:
    return FileResponse(STATIC_DIR / "index.html")


@app.get("/api/config")
def api_config() -> dict[str, Any]:
    return {
        "org": cfg.GITHUB_ORG,
        "filter": cfg.PR_SEARCH_FILTER,
        "model": cfg.FIREWORKS_MODEL,
        "mention_authors": cfg.MENTION_AUTHORS,
    }


@app.get("/api/handbook")
def api_handbook() -> dict[str, Any]:
    h = handbook()
    if h is None:
        return {
            "enabled": False,
            "head_sha": None,
            "distilled_at": None,
            "digest_chars": 0,
        }
    return h.status()


@app.get("/api/prs")
def api_prs() -> dict[str, Any]:
    try:
        prs = gh().search_prs()
        return {"prs": prs, "me": gh().whoami()}
    except GitHubError as e:
        raise HTTPException(400, str(e))


def _serialize_review(row: dict[str, Any]) -> dict[str, Any]:
    review = None
    if row.get("review_json"):
        try:
            review = json.loads(row["review_json"])
        except (json.JSONDecodeError, TypeError):
            review = None
    return {
        "owner": row["owner"],
        "repo": row["repo"],
        "number": row["number"],
        "title": row.get("pr_title"),
        "author": row.get("pr_author"),
        "url": row.get("pr_url"),
        "status": row["status"],
        "updated_at": row.get("pr_updated_at"),
        "created_at": row.get("pr_created_at"),
        "node_id": row.get("pr_node_id"),
        "cached_at": row.get("cached_at"),
        "attempts": row.get("attempts", 0),
        "error": row.get("error"),
        "review": review,
    }


@app.get("/api/reviews")
def api_reviews() -> dict[str, Any]:
    s = store()
    if s is None:
        raise HTTPException(503, "Review worker is not running yet.")
    rows = s.list()
    return {
        "reviews": [_serialize_review(r) for r in rows],
        "poll_interval": cfg.POLL_INTERVAL,
    }


@app.post("/api/refresh")
def api_refresh() -> JSONResponse:
    w = worker()
    if w is None:
        raise HTTPException(503, "Review worker is not running yet.")
    w.trigger()  # non-blocking: the worker thread runs the cycle
    return JSONResponse(status_code=202, content={"ok": True, "scheduled": True})


class ReviewReq(BaseModel):
    owner: str
    repo: str
    number: int
    title: str = ""
    author: str = ""
    body: str = ""


def _cache_write_through(req: ReviewReq, diff: str, result: dict[str, Any]) -> None:
    """Best-effort: store an on-demand review in the cache so the dashboard and
    the worker share one source of truth. Never fails the request."""
    if _store is None:
        return
    try:
        _store.upsert(
            req.owner,
            req.repo,
            req.number,
            status="ready",
            diff_hash=hashlib.sha256(diff.encode("utf-8", "ignore")).hexdigest(),
            review_json=json.dumps(result),
            error=None,
            attempts=0,
            pr_title=req.title,
            pr_author=req.author,
        )
    except Exception:  # noqa: BLE001 - caching is best-effort
        pass


@app.post("/api/review")
def api_review(req: ReviewReq) -> dict[str, Any]:
    try:
        diff = gh().pr_diff(req.owner, req.repo, req.number)
        pr = req.model_dump()
        result = reviewer().review(pr, diff)
        _cache_write_through(req, diff, result)
        return {"review": result}
    except GitHubError as e:
        raise HTTPException(400, str(e))
    except Exception as e:  # surface Fireworks/parse errors to the UI
        raise HTTPException(500, f"Review failed: {e}")


class ReviseReq(ReviewReq):
    notes: str  # the user's requested changes to the review


@app.post("/api/revise")
def api_revise(req: ReviseReq) -> dict[str, Any]:
    try:
        diff = gh().pr_diff(req.owner, req.repo, req.number)
        pr = req.model_dump()
        # Fold the user's revision notes into the diff context as a trusted
        # reviewer instruction (distinct from the untrusted diff).
        annotated = (
            f"{diff}\n\n--- REVIEWER REVISION NOTES (trusted, from the human "
            f"reviewer, not from the PR) ---\n{req.notes}"
        )
        result = reviewer().review(pr, annotated)
        return {"review": result}
    except GitHubError as e:
        raise HTTPException(400, str(e))
    except Exception as e:  # surface Fireworks/parse errors to the UI
        raise HTTPException(500, f"Revision failed: {e}")


class PostReq(BaseModel):
    owner: str
    repo: str
    number: int
    body: str
    event: str  # COMMENT | APPROVE | REQUEST_CHANGES


@app.post("/api/post")
def api_post(req: PostReq) -> dict[str, Any]:
    try:
        res = gh().submit_review(req.owner, req.repo, req.number, req.body, req.event)
        return {"ok": True, "html_url": res.get("html_url", "")}
    except GitHubError as e:
        raise HTTPException(400, str(e))


class AutomergeReq(BaseModel):
    owner: str
    repo: str
    number: int
    node_id: str
    method: str = "SQUASH"  # SQUASH | MERGE | REBASE


@app.post("/api/automerge")
def api_automerge(req: AutomergeReq) -> dict[str, Any]:
    try:
        res = gh().enable_automerge(req.node_id, req.method)
        return {"ok": True, "result": res}
    except GitHubError as e:
        raise HTTPException(400, str(e))


def main() -> None:
    import uvicorn

    uvicorn.run(app, host=cfg.HOST, port=cfg.PORT)


if __name__ == "__main__":
    main()