# app/services/chain.py — chain + node CRUD and branching tree logic
from __future__ import annotations

import sqlite3
import time
import uuid
from typing import Any


# ── Chain CRUD ────────────────────────────────────────────────────────────────

def create_chain(conn: sqlite3.Connection, name: str) -> dict[str, Any]:
    chain_id = str(uuid.uuid4())
    now = time.time()
    conn.execute(
        "INSERT INTO chains (id, name, created_at) VALUES (?, ?, ?)",
        (chain_id, name, now),
    )
    conn.commit()
    return {"id": chain_id, "name": name, "created_at": now, "node_count": 0}


def list_chains(conn: sqlite3.Connection) -> list[dict[str, Any]]:
    rows = conn.execute("""
        SELECT c.id, c.name, c.created_at,
               COUNT(n.id) AS node_count
        FROM chains c
        LEFT JOIN nodes n ON n.chain_id = c.id
        GROUP BY c.id
        ORDER BY c.created_at DESC
    """).fetchall()
    return [dict(r) for r in rows]


def get_chain(conn: sqlite3.Connection, chain_id: str) -> dict[str, Any] | None:
    row = conn.execute(
        "SELECT id, name, created_at FROM chains WHERE id = ?", (chain_id,)
    ).fetchone()
    if row is None:
        return None
    nodes = _get_nodes_for_chain(conn, chain_id)
    return {"id": row["id"], "name": row["name"], "created_at": row["created_at"], "nodes": nodes}


def delete_chain(conn: sqlite3.Connection, chain_id: str) -> bool:
    cur = conn.execute("DELETE FROM chains WHERE id = ?", (chain_id,))
    conn.commit()
    return cur.rowcount > 0


# ── Node CRUD ─────────────────────────────────────────────────────────────────

def create_root_node(
    conn: sqlite3.Connection,
    chain_id: str,
    audio_path: str,
    duration_s: float,
) -> dict[str, Any]:
    """Create the root node (uploaded source audio). Always committed."""
    node_id = str(uuid.uuid4())
    now = time.time()
    conn.execute("""
        INSERT INTO nodes
          (id, chain_id, parent_id, audio_path, duration_s, status,
           is_committed, prompt, cfg_coef, prompt_duration_s, created_at)
        VALUES (?, ?, NULL, ?, ?, 'ready', 1, '', 3.0, 10.0, ?)
    """, (node_id, chain_id, audio_path, duration_s, now))
    conn.commit()
    return get_node(conn, node_id)


def get_node(conn: sqlite3.Connection, node_id: str) -> dict[str, Any] | None:
    row = conn.execute("SELECT * FROM nodes WHERE id = ?", (node_id,)).fetchone()
    return _row_to_dict(row) if row else None


def create_branch_node(
    conn: sqlite3.Connection,
    parent_id: str,
    chain_id: str,
    prompt: str,
    energy: float | None,
    tempo_feel: float | None,
    density: float | None,
    cfg_coef: float,
    prompt_duration_s: float,
) -> dict[str, Any]:
    """Create a new branch node in 'pending' state. Caller updates to 'generating'."""
    node_id = str(uuid.uuid4())
    now = time.time()
    conn.execute("""
        INSERT INTO nodes
          (id, chain_id, parent_id, audio_path, duration_s, status,
           is_committed, prompt, energy, tempo_feel, density,
           cfg_coef, prompt_duration_s, created_at)
        VALUES (?, ?, ?, NULL, NULL, 'pending', 0, ?, ?, ?, ?, ?, ?, ?)
    """, (node_id, chain_id, parent_id, prompt, energy, tempo_feel, density,
          cfg_coef, prompt_duration_s, now))
    conn.commit()
    return get_node(conn, node_id)


def update_node_status(
    conn: sqlite3.Connection,
    node_id: str,
    status: str,
    audio_path: str | None = None,
    duration_s: float | None = None,
    error_msg: str | None = None,
) -> dict[str, Any] | None:
    fields: list[str] = ["status = ?"]
    values: list[Any] = [status]
    if audio_path is not None:
        fields.append("audio_path = ?")
        values.append(audio_path)
    if duration_s is not None:
        fields.append("duration_s = ?")
        values.append(duration_s)
    if error_msg is not None:
        fields.append("error_msg = ?")
        values.append(error_msg)
    values.append(node_id)
    conn.execute(f"UPDATE nodes SET {', '.join(fields)} WHERE id = ?", values)
    conn.commit()
    return get_node(conn, node_id)


def commit_node(conn: sqlite3.Connection, node_id: str) -> dict[str, Any] | None:
    """
    Promote a branch node to the committed spine.

    Discard (delete) all sibling branch nodes (same parent, not committed).
    The committed node and all its ancestors remain. Root is always committed.
    """
    node = get_node(conn, node_id)
    if node is None:
        return None

    parent_id = node.get("parent_id")
    if parent_id:
        # Discard non-committed siblings (same parent)
        conn.execute("""
            DELETE FROM nodes
            WHERE parent_id = ? AND id != ? AND is_committed = 0
        """, (parent_id, node_id))

    conn.execute("UPDATE nodes SET is_committed = 1 WHERE id = ?", (node_id,))
    conn.commit()
    return get_node(conn, node_id)


def delete_node(conn: sqlite3.Connection, node_id: str) -> bool:
    """Delete a branch node. Root nodes (parent_id IS NULL) cannot be deleted."""
    row = conn.execute(
        "SELECT parent_id FROM nodes WHERE id = ?", (node_id,)
    ).fetchone()
    if row is None or row["parent_id"] is None:
        return False  # root node; refuse
    cur = conn.execute(
        "DELETE FROM nodes WHERE id = ? AND is_committed = 0", (node_id,)
    )
    conn.commit()
    return cur.rowcount > 0


def get_committed_spine(conn: sqlite3.Connection, chain_id: str) -> list[dict[str, Any]]:
    """
    Return committed nodes ordered root → leaf along the committed spine.

    Uses a recursive CTE to walk the tree from the root through committed nodes.
    """
    rows = conn.execute("""
        WITH RECURSIVE spine(id, parent_id, depth) AS (
            SELECT id, parent_id, 0
            FROM nodes
            WHERE chain_id = ? AND parent_id IS NULL AND is_committed = 1
            UNION ALL
            SELECT n.id, n.parent_id, spine.depth + 1
            FROM nodes n
            JOIN spine ON n.parent_id = spine.id
            WHERE n.is_committed = 1 AND n.chain_id = ?
        )
        SELECT n.* FROM nodes n
        JOIN spine ON spine.id = n.id
        ORDER BY spine.depth
    """, (chain_id, chain_id)).fetchall()
    return [_row_to_dict(r) for r in rows]


# ── Helpers ───────────────────────────────────────────────────────────────────

def _row_to_dict(row: sqlite3.Row) -> dict[str, Any]:
    d = dict(row)
    d["is_committed"] = bool(d.get("is_committed", 0))
    d["children"] = []
    return d


def _get_nodes_for_chain(conn: sqlite3.Connection, chain_id: str) -> list[dict[str, Any]]:
    rows = conn.execute(
        "SELECT * FROM nodes WHERE chain_id = ? ORDER BY created_at", (chain_id,)
    ).fetchall()
    return [_row_to_dict(r) for r in rows]