"""SQLite database schema and connection management."""

import sqlite3
from contextlib import contextmanager
from pathlib import Path
from typing import Generator

import atocore.config as _config
from atocore.observability.logger import get_logger

log = get_logger("database")

SCHEMA_SQL = """
CREATE TABLE IF NOT EXISTS source_documents (
    id TEXT PRIMARY KEY,
    file_path TEXT UNIQUE NOT NULL,
    file_hash TEXT NOT NULL,
    title TEXT,
    doc_type TEXT DEFAULT 'markdown',
    tags TEXT DEFAULT '[]',
    ingested_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS source_chunks (
    id TEXT PRIMARY KEY,
    document_id TEXT NOT NULL REFERENCES source_documents(id) ON DELETE CASCADE,
    chunk_index INTEGER NOT NULL,
    content TEXT NOT NULL,
    heading_path TEXT DEFAULT '',
    char_count INTEGER NOT NULL,
    metadata TEXT DEFAULT '{}',
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS memories (
    id TEXT PRIMARY KEY,
    memory_type TEXT NOT NULL,
    content TEXT NOT NULL,
    project TEXT DEFAULT '',
    source_chunk_id TEXT REFERENCES source_chunks(id),
    confidence REAL DEFAULT 1.0,
    status TEXT DEFAULT 'active',
    last_referenced_at DATETIME,
    reference_count INTEGER DEFAULT 0,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS projects (
    id TEXT PRIMARY KEY,
    name TEXT UNIQUE NOT NULL,
    description TEXT DEFAULT '',
    status TEXT DEFAULT 'active',
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS interactions (
    id TEXT PRIMARY KEY,
    prompt TEXT NOT NULL,
    context_pack TEXT DEFAULT '{}',
    response_summary TEXT DEFAULT '',
    response TEXT DEFAULT '',
    memories_used TEXT DEFAULT '[]',
    chunks_used TEXT DEFAULT '[]',
    client TEXT DEFAULT '',
    session_id TEXT DEFAULT '',
    project TEXT DEFAULT '',
    project_id TEXT REFERENCES projects(id),
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

-- Indexes that reference columns guaranteed to exist since the first
-- release ship here. Indexes that reference columns added by later
-- migrations (memories.project, interactions.project,
-- interactions.session_id) are created inside _apply_migrations AFTER
-- the corresponding ALTER TABLE, NOT here. Creating them here would
-- fail on upgrade from a pre-migration schema because CREATE TABLE
-- IF NOT EXISTS is a no-op on an existing table, so the new columns
-- wouldn't be added before the CREATE INDEX runs.
CREATE INDEX IF NOT EXISTS idx_chunks_document ON source_chunks(document_id);
CREATE INDEX IF NOT EXISTS idx_memories_type ON memories(memory_type);
CREATE INDEX IF NOT EXISTS idx_memories_status ON memories(status);
CREATE INDEX IF NOT EXISTS idx_interactions_project ON interactions(project_id);
"""


def _ensure_data_dir() -> None:
    _config.ensure_runtime_dirs()


def init_db() -> None:
    """Initialize the database with schema."""
    _ensure_data_dir()
    with get_connection() as conn:
        conn.executescript(SCHEMA_SQL)
        _apply_migrations(conn)
    log.info("database_initialized", path=str(_config.settings.db_path))


def _apply_migrations(conn: sqlite3.Connection) -> None:
    """Apply lightweight schema migrations for existing local databases."""
    if not _column_exists(conn, "memories", "project"):
        conn.execute("ALTER TABLE memories ADD COLUMN project TEXT DEFAULT ''")
    conn.execute("CREATE INDEX IF NOT EXISTS idx_memories_project ON memories(project)")

    # Phase 9 Commit B: reinforcement columns.
    # last_referenced_at records when a memory was most recently referenced
    # in a captured interaction; reference_count is a monotonically
    # increasing counter bumped on every reference. Together they let
    # Reflection (Commit C) and decay (deferred) reason about which
    # memories are actually being used versus which have gone cold.
    if not _column_exists(conn, "memories", "last_referenced_at"):
        conn.execute("ALTER TABLE memories ADD COLUMN last_referenced_at DATETIME")
    if not _column_exists(conn, "memories", "reference_count"):
        conn.execute("ALTER TABLE memories ADD COLUMN reference_count INTEGER DEFAULT 0")
    conn.execute(
        "CREATE INDEX IF NOT EXISTS idx_memories_last_referenced ON memories(last_referenced_at)"
    )

    # Phase 9 Commit A: capture loop columns on the interactions table.
    # The original schema only carried prompt + project_id + a context_pack
    # JSON blob. To make interactions a real audit trail of what AtoCore fed
    # the LLM and what came back, we record the full response, the chunk
    # and memory ids that were actually used, plus client + session metadata.
    if not _column_exists(conn, "interactions", "response"):
        conn.execute("ALTER TABLE interactions ADD COLUMN response TEXT DEFAULT ''")
    if not _column_exists(conn, "interactions", "memories_used"):
        conn.execute("ALTER TABLE interactions ADD COLUMN memories_used TEXT DEFAULT '[]'")
    if not _column_exists(conn, "interactions", "chunks_used"):
        conn.execute("ALTER TABLE interactions ADD COLUMN chunks_used TEXT DEFAULT '[]'")
    if not _column_exists(conn, "interactions", "client"):
        conn.execute("ALTER TABLE interactions ADD COLUMN client TEXT DEFAULT ''")
    if not _column_exists(conn, "interactions", "session_id"):
        conn.execute("ALTER TABLE interactions ADD COLUMN session_id TEXT DEFAULT ''")
    if not _column_exists(conn, "interactions", "project"):
        conn.execute("ALTER TABLE interactions ADD COLUMN project TEXT DEFAULT ''")
    conn.execute(
        "CREATE INDEX IF NOT EXISTS idx_interactions_session ON interactions(session_id)"
    )
    conn.execute(
        "CREATE INDEX IF NOT EXISTS idx_interactions_project_name ON interactions(project)"
    )
    conn.execute(
        "CREATE INDEX IF NOT EXISTS idx_interactions_created_at ON interactions(created_at)"
    )


def _column_exists(conn: sqlite3.Connection, table: str, column: str) -> bool:
    rows = conn.execute(f"PRAGMA table_info({table})").fetchall()
    return any(row["name"] == column for row in rows)


@contextmanager
def get_connection() -> Generator[sqlite3.Connection, None, None]:
    """Get a database connection with row factory."""
    _ensure_data_dir()
    conn = sqlite3.connect(
        str(_config.settings.db_path),
        timeout=_config.settings.db_busy_timeout_ms / 1000,
    )
    conn.row_factory = sqlite3.Row
    conn.execute("PRAGMA foreign_keys = ON")
    conn.execute(f"PRAGMA busy_timeout = {_config.settings.db_busy_timeout_ms}")
    conn.execute("PRAGMA journal_mode = WAL")
    conn.execute("PRAGMA synchronous = NORMAL")
    try:
        yield conn
        conn.commit()
    except Exception:
        conn.rollback()
        raise
    finally:
        conn.close()