import sqlite3
import os
import threading

FORUM_DB = "forum.db"


class ForumDB:
    def __init__(self, data_dir):
        self.path = os.path.join(data_dir, FORUM_DB)
        self._pool = []
        self._pool_lock = threading.Lock()
        self._POOL_SIZE = 8
        self.init_db()

    def init_db(self):
        os.makedirs(os.path.dirname(self.path), exist_ok=True)
        db = sqlite3.connect(self.path)
        db.execute(
            "CREATE TABLE IF NOT EXISTS threads ("
            "  id TEXT PRIMARY KEY,"
            "  title TEXT NOT NULL,"
            "  url TEXT DEFAULT '',"
            "  body TEXT DEFAULT '',"
            "  tags TEXT DEFAULT '',"
            "  author_instance TEXT NOT NULL,"
            "  author_name TEXT DEFAULT '',"
            "  created_at TEXT NOT NULL,"
            "  updated_at TEXT NOT NULL,"
            "  score INTEGER DEFAULT 0"
            ")"
        )
        db.execute(
            "CREATE TABLE IF NOT EXISTS posts ("
            "  id TEXT PRIMARY KEY,"
            "  thread_id TEXT NOT NULL,"
            "  parent_id TEXT DEFAULT '',"
            "  body TEXT NOT NULL,"
            "  author_instance TEXT NOT NULL,"
            "  author_name TEXT DEFAULT '',"
            "  created_at TEXT NOT NULL,"
            "  FOREIGN KEY (thread_id) REFERENCES threads(id)"
            ")"
        )
        db.execute(
            "CREATE TABLE IF NOT EXISTS upvotes ("
            "  thread_id TEXT NOT NULL,"
            "  instance_hash TEXT NOT NULL,"
            "  PRIMARY KEY (thread_id, instance_hash)"
            ")"
        )
        db.execute(
            "CREATE TABLE IF NOT EXISTS synced_instances ("
            "  instance_hash TEXT PRIMARY KEY,"
            "  name TEXT DEFAULT '',"
            "  last_sync TEXT DEFAULT ''"
            ")"
        )
        db.execute(
            "CREATE TABLE IF NOT EXISTS settings ("
            "  key TEXT PRIMARY KEY,"
            "  value TEXT"
            ")"
        )
        db.execute("CREATE INDEX IF NOT EXISTS idx_posts_thread ON posts(thread_id)")
        db.execute("CREATE INDEX IF NOT EXISTS idx_posts_created ON posts(created_at)")
        db.execute("CREATE INDEX IF NOT EXISTS idx_threads_updated ON threads(updated_at)")
        db.execute("CREATE INDEX IF NOT EXISTS idx_threads_created ON threads(created_at)")
        db.commit()
        db.close()

    def get_db(self):
        with self._pool_lock:
            if self._pool:
                db = self._pool.pop()
                try:
                    db.execute("SELECT 1")
                    return db
                except Exception:
                    pass
        db = sqlite3.connect(self.path, timeout=10)
        db.execute("PRAGMA journal_mode=WAL")
        db.row_factory = sqlite3.Row
        return db

    def return_db(self, db):
        try:
            db.rollback()
        except Exception:
            try:
                db.close()
            except Exception:
                pass
            return
        with self._pool_lock:
            if len(self._pool) < self._POOL_SIZE:
                self._pool.append(db)
            else:
                db.close()

    def get_setting(self, key, default=""):
        db = self.get_db()
        try:
            row = db.execute("SELECT value FROM settings WHERE key = ?", (key,)).fetchone()
            return row["value"] if row else default
        finally:
            self.return_db(db)

    def set_setting(self, key, value):
        db = self.get_db()
        try:
            db.execute(
                "INSERT INTO settings (key, value) VALUES (?, ?) "
                "ON CONFLICT(key) DO UPDATE SET value=excluded.value",
                (key, value),
            )
            db.commit()
        finally:
            self.return_db(db)

    def get_thread(self, thread_id):
        db = self.get_db()
        try:
            return db.execute(
                "SELECT * FROM threads WHERE id = ?", (thread_id,)
            ).fetchone()
        finally:
            self.return_db(db)

    def get_posts(self, thread_id):
        db = self.get_db()
        try:
            return db.execute(
                "SELECT * FROM posts WHERE thread_id = ? ORDER BY created_at ASC",
                (thread_id,),
            ).fetchall()
        finally:
            self.return_db(db)

    def get_threads(self, page=1, per_page=20, tag="", search=""):
        db = self.get_db()
        try:
            offset = (page - 1) * per_page
            params = []
            where = []
            if tag:
                where.append("t.tags LIKE ?")
                params.append(f"%{tag}%")
            if search:
                where.append("(t.title LIKE ? OR t.body LIKE ?)")
                params.extend([f"%{search}%", f"%{search}%"])
            where_clause = (" WHERE " + " AND ".join(where)) if where else ""
            total = db.execute(
                f"SELECT count(*) FROM threads t{where_clause}", params
            ).fetchone()[0]
            rows = db.execute(
                f"SELECT t.*, (SELECT count(*) FROM posts p WHERE p.thread_id = t.id) AS reply_count "
                f"FROM threads t{where_clause} ORDER BY t.updated_at DESC LIMIT ? OFFSET ?",
                params + [per_page, offset],
            ).fetchall()
            return rows, total
        finally:
            self.return_db(db)

    def create_thread(self, thread_id, title, url, body, tags, author_instance, author_name, now):
        db = self.get_db()
        try:
            db.execute(
                "INSERT INTO threads (id, title, url, body, tags, author_instance, author_name, created_at, updated_at) "
                "VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)",
                (thread_id, title, url, body, tags, author_instance, author_name, now, now),
            )
            db.commit()
        finally:
            self.return_db(db)

    def create_post(self, post_id, thread_id, parent_id, body, author_instance, author_name, now):
        db = self.get_db()
        try:
            db.execute(
                "INSERT INTO posts (id, thread_id, parent_id, body, author_instance, author_name, created_at) "
                "VALUES (?, ?, ?, ?, ?, ?, ?)",
                (post_id, thread_id, parent_id, body, author_instance, author_name, now),
            )
            db.execute("UPDATE threads SET updated_at = ? WHERE id = ?", (now, thread_id))
            db.commit()
        finally:
            self.return_db(db)

    def toggle_upvote(self, thread_id, instance_hash):
        db = self.get_db()
        try:
            row = db.execute(
                "SELECT 1 FROM upvotes WHERE thread_id = ? AND instance_hash = ?",
                (thread_id, instance_hash),
            ).fetchone()
            if row:
                db.execute(
                    "DELETE FROM upvotes WHERE thread_id = ? AND instance_hash = ?",
                    (thread_id, instance_hash),
                )
                db.execute("UPDATE threads SET score = score - 1 WHERE id = ?", (thread_id,))
                delta = -1
            else:
                db.execute(
                    "INSERT INTO upvotes (thread_id, instance_hash) VALUES (?, ?)",
                    (thread_id, instance_hash),
                )
                db.execute("UPDATE threads SET score = score + 1 WHERE id = ?", (thread_id,))
                delta = 1
            db.commit()
            return delta
        finally:
            self.return_db(db)

    def get_synced_instances(self):
        db = self.get_db()
        try:
            return db.execute("SELECT * FROM synced_instances").fetchall()
        finally:
            self.return_db(db)

    def upsert_synced_instance(self, instance_hash, name=""):
        db = self.get_db()
        try:
            db.execute(
                "INSERT INTO synced_instances (instance_hash, name) VALUES (?, ?) "
                "ON CONFLICT(instance_hash) DO UPDATE SET name=excluded.name",
                (instance_hash, name),
            )
            db.commit()
        finally:
            self.return_db(db)

    def remove_synced_instance(self, instance_hash):
        db = self.get_db()
        try:
            db.execute("DELETE FROM synced_instances WHERE instance_hash = ?", (instance_hash,))
            db.commit()
        finally:
            self.return_db(db)

    def update_last_sync(self, instance_hash, now):
        db = self.get_db()
        try:
            db.execute(
                "UPDATE synced_instances SET last_sync = ? WHERE instance_hash = ?",
                (now, instance_hash),
            )
            db.commit()
        finally:
            self.return_db(db)

    def set_last_sync(self, instance_hash, timestamp):
        self.update_last_sync(instance_hash, timestamp)

    def get_new_content(self, since):
        db = self.get_db()
        try:
            threads = db.execute(
                "SELECT * FROM threads WHERE updated_at > ? ORDER BY updated_at ASC",
                (since,),
            ).fetchall()
            posts = db.execute(
                "SELECT * FROM posts WHERE created_at > ? ORDER BY created_at ASC",
                (since,),
            ).fetchall()
            upvote_threads = db.execute(
                "SELECT thread_id FROM upvotes u "
                "WHERE NOT EXISTS (SELECT 1 FROM threads t WHERE t.id = u.thread_id AND t.updated_at > ?)",
                (since,),
            ).fetchall()
            return threads, posts, [r["thread_id"] for r in upvote_threads]
        finally:
            self.return_db(db)

    def merge_thread(self, thread):
        db = self.get_db()
        try:
            existing = db.execute("SELECT updated_at FROM threads WHERE id = ?", (thread["id"],)).fetchone()
            if existing and existing["updated_at"] >= thread["updated_at"]:
                return
            db.execute(
                "INSERT INTO threads (id, title, url, body, tags, author_instance, author_name, created_at, updated_at, score) "
                "VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?) "
                "ON CONFLICT(id) DO UPDATE SET "
                "title=excluded.title, url=excluded.url, body=excluded.body, "
                "tags=excluded.tags, updated_at=excluded.updated_at",
                (thread["id"], thread["title"], thread["url"], thread["body"],
                 thread["tags"], thread["author_instance"], thread["author_name"],
                 thread["created_at"], thread["updated_at"], thread["score"]),
            )
            db.commit()
        finally:
            self.return_db(db)

    def merge_post(self, post):
        db = self.get_db()
        try:
            db.execute(
                "INSERT OR IGNORE INTO posts (id, thread_id, parent_id, body, author_instance, author_name, created_at) "
                "VALUES (?, ?, ?, ?, ?, ?, ?)",
                (post["id"], post["thread_id"], post["parent_id"], post["body"],
                 post["author_instance"], post["author_name"], post["created_at"]),
            )
            db.commit()
        finally:
            self.return_db(db)

    def merge_upvote(self, thread_id, instance_hash):
        db = self.get_db()
        try:
            db.execute(
                "INSERT OR IGNORE INTO upvotes (thread_id, instance_hash) VALUES (?, ?)",
                (thread_id, instance_hash),
            )
            if db.total_changes:
                db.execute("UPDATE threads SET score = score + 1 WHERE id = ?", (thread_id,))
            db.commit()
        finally:
            self.return_db(db)