"""Database operations for the AI Research Oracle.

Handles connections, schema initialization, and common queries.
"""
import os
import sqlite3
from typing import Optional

from oracle.config import DB_PATH, SCHEMA_PATH, SOURCE_TIERS


def get_connection(db_path: Optional[str] = None) -> sqlite3.Connection:
    """Open a database connection."""
    path = db_path or str(DB_PATH)
    conn = sqlite3.connect(path)
    conn.row_factory = sqlite3.Row
    return conn


def get_ro_connection(db_path: Optional[str] = None) -> sqlite3.Connection:
    """Open a read-only database connection."""
    path = db_path or str(DB_PATH)
    return sqlite3.connect(f"file:{path}?mode=ro", uri=True)


def init_db(db_path: Optional[str] = None, schema_path: Optional[str] = None) -> sqlite3.Connection:
    """Initialize or open the database, applying schema if it exists.

    Schema uses CREATE IF NOT EXISTS so repeated calls are idempotent.
    Also runs World Monitor migration columns (content_hash, verdict, freshness).
    """
    conn = sqlite3.connect(db_path or str(DB_PATH))
    sp = schema_path or str(SCHEMA_PATH)
    if os.path.exists(sp):
        with open(sp) as f:
            conn.executescript(f.read())
        conn.commit()
    # World Monitor migration columns (idempotent)
    for col in [
        "content_hash TEXT DEFAULT ''",
        "verdict TEXT DEFAULT ''",
        "source_tier INTEGER DEFAULT 2",
    ]:
        try:
            conn.execute(f"ALTER TABLE entries ADD COLUMN {col}")
        except sqlite3.OperationalError:
            pass  # already exists
    conn.commit()
    return conn


def migrate_world_monitor(conn: Optional[sqlite3.Connection] = None) -> dict:
    """Apply World Monitor schema migrations + backfill.

    Returns: {columns_added: int, hashes_backfilled: int, verdicts_set: int}
    """
    from oracle.dedup import backfill_hashes, apply_verdicts, get_source_tier

    c = conn or get_connection()
    cur = c.cursor()

    # Check which columns already exist
    cur.execute("PRAGMA table_info(entries)")
    existing = {row[1] for row in cur.fetchall()}

    columns_to_add = []
    if "content_hash" not in existing:
        columns_to_add.append("content_hash TEXT DEFAULT ''")
    if "verdict" not in existing:
        columns_to_add.append("verdict TEXT DEFAULT ''")
    if "source_tier" not in existing:
        columns_to_add.append("source_tier INTEGER DEFAULT 2")

    added = 0
    for col_def in columns_to_add:
        try:
            cur.execute(f"ALTER TABLE entries ADD COLUMN {col_def}")
            added += 1
        except sqlite3.OperationalError:
            pass  # race condition or already exists

    c.commit()

    # Backfill content hashes
    hashes = backfill_hashes(c)

    # Backfill source tiers — reset first so the WHERE clause catches everything
    cur.execute("UPDATE entries SET source_tier = 0")
    c.commit()
    for source_name, tier_info in SOURCE_TIERS.items():
        cur.execute(
            "UPDATE entries SET source_tier = ? WHERE source = ?",
            (tier_info["tier"], source_name),
        )
    c.commit()

    # Set verdicts
    verdicts = apply_verdicts(c)

    return {"columns_added": added, "hashes_backfilled": hashes, "verdicts_set": verdicts}


def get_stats(conn: sqlite3.Connection) -> dict:
    """Return database statistics."""
    cur = conn.cursor()

    cur.execute("SELECT COUNT(*) FROM entries")
    total = cur.fetchone()[0]

    cur.execute("""
        SELECT source, COUNT(*) as cnt, ROUND(AVG(signal_score), 2) as avg_score,
               MIN(signal_score) as min_score, MAX(signal_score) as max_score
        FROM entries GROUP BY source
    """)
    sources = {r["source"]: dict(r) for r in cur.fetchall()}

    cur.execute("SELECT COUNT(*) FROM entries WHERE summary IS NOT NULL")
    summarized = cur.fetchone()[0]

    cur.execute("SELECT COUNT(*) FROM entries WHERE summary IS NULL")
    pending = cur.fetchone()[0]

    # Bucket distribution
    try:
        cur.execute("""
            SELECT bucket, COUNT(*) as cnt
            FROM entries WHERE bucket IS NOT NULL
            GROUP BY bucket ORDER BY cnt DESC
        """)
        buckets = {r["bucket"]: r["cnt"] for r in cur.fetchall()}
    except Exception:
        buckets = {}

    return {
        "total_entries": total,
        "sources": sources,
        "summarized": summarized,
        "pending_summary": pending,
        "buckets": buckets,
    }


def query_top(conn: sqlite3.Connection, n: int = 10,
              source: Optional[str] = None,
              min_score: float = 0) -> list[dict]:
    """Get top N entries by signal score."""
    cur = conn.cursor()
    where_parts = []
    params = []

    if min_score > 0:
        where_parts.append("signal_score >= ?")
        params.append(min_score)
    if source:
        where_parts.append("source = ?")
        params.append(source)

    where = (" AND " + " AND ".join(where_parts)) if where_parts else ""
    cur.execute(
        f"SELECT * FROM entries {where} ORDER BY signal_score DESC LIMIT ?",
        params + [n],
    )
    return [dict(r) for r in cur.fetchall()]


def query_recent(conn: sqlite3.Connection, hours: int = 24) -> list[dict]:
    """Get entries from the last N hours."""
    from datetime import datetime, timezone, timedelta

    cutoff = (datetime.now(timezone.utc) - timedelta(hours=hours)).strftime(
        "%Y-%m-%dT%H:%M:%SZ"
    )
    cur = conn.cursor()
    cur.execute(
        "SELECT * FROM entries WHERE first_seen >= ? ORDER BY first_seen DESC",
        (cutoff,),
    )
    return [dict(r) for r in cur.fetchall()]


def query_search(conn: sqlite3.Connection, q: str, limit: int = 20) -> list[dict]:
    """Search entries by title, summary, and key technical point."""
    cur = conn.cursor()
    pattern = f"%{q}%"
    cur.execute("""
        SELECT * FROM entries
        WHERE title LIKE ?
           OR json_extract(summary,'$.one_liner') LIKE ?
           OR json_extract(summary,'$.key_technical_point') LIKE ?
        ORDER BY signal_score DESC LIMIT ?
    """, (pattern, pattern, pattern, limit))
    return [dict(r) for r in cur.fetchall()]


def query_by_tag(conn: sqlite3.Connection, tag: str, limit: int = 20) -> list[dict]:
    """Get entries matching a category tag."""
    cur = conn.cursor()
    cur.execute("""
        SELECT * FROM entries
        WHERE json_extract(category_tags,'$') LIKE ?
        ORDER BY signal_score DESC LIMIT ?
    """, (f'%"{tag}"%', limit))
    return [dict(r) for r in cur.fetchall()]