"""Replay API router -- conversation listing and step-by-step replay."""

from __future__ import annotations

import re
from typing import TYPE_CHECKING, Annotated, Any

from fastapi import APIRouter, HTTPException, Query, Request

_THREAD_ID_PATTERN = re.compile(r"^[a-zA-Z0-9\-_]{1,128}$")

if TYPE_CHECKING:
    from psycopg_pool import AsyncConnectionPool

router = APIRouter(prefix="/api", tags=["replay"])

_LIST_CONVERSATIONS_SQL = """
SELECT thread_id, created_at, last_activity, status, total_tokens, total_cost_usd
FROM conversations
ORDER BY last_activity DESC
LIMIT %(limit)s OFFSET %(offset)s
"""

_GET_CHECKPOINTS_SQL = """
SELECT thread_id, checkpoint_id, checkpoint, metadata
FROM checkpoints
WHERE thread_id = %(thread_id)s
ORDER BY checkpoint_id ASC
"""


async def get_pool(request: Request) -> AsyncConnectionPool:
    """Dependency: extract the shared pool from app state."""
    return request.app.state.pool


def _envelope(data: Any, *, success: bool = True, error: str | None = None) -> dict:
    return {"success": success, "data": data, "error": error}


@router.get("/conversations")
async def list_conversations(
    request: Request,
    page: Annotated[int, Query(ge=1)] = 1,
    per_page: Annotated[int, Query(ge=1, le=100)] = 20,
) -> dict:
    """List conversations with pagination."""
    pool = await get_pool(request)
    offset = (page - 1) * per_page
    async with pool.connection() as conn:
        cursor = await conn.execute(
            _LIST_CONVERSATIONS_SQL,
            {"limit": per_page, "offset": offset},
        )
        rows = await cursor.fetchall()

    return _envelope([dict(row) for row in rows])


@router.get("/replay/{thread_id}")
async def get_replay(
    thread_id: str,
    request: Request,
    page: Annotated[int, Query(ge=1)] = 1,
    per_page: Annotated[int, Query(ge=1, le=100)] = 20,
) -> dict:
    """Return paginated replay steps for a conversation thread."""
    from app.replay.transformer import transform_checkpoints

    if not _THREAD_ID_PATTERN.match(thread_id):
        raise HTTPException(status_code=400, detail="Invalid thread_id format")

    pool = await get_pool(request)
    async with pool.connection() as conn:
        cursor = await conn.execute(_GET_CHECKPOINTS_SQL, {"thread_id": thread_id})
        rows = await cursor.fetchall()

    if not rows:
        raise HTTPException(status_code=404, detail="Thread not found")

    all_steps = transform_checkpoints([dict(row) for row in rows])
    total_steps = len(all_steps)
    start = (page - 1) * per_page
    end = start + per_page
    page_steps = all_steps[start:end]

    data = {
        "thread_id": thread_id,
        "total_steps": total_steps,
        "page": page,
        "per_page": per_page,
        "steps": [
            {
                "step": s.step,
                "type": s.type.value,
                "timestamp": s.timestamp,
                "content": s.content,
                "agent": s.agent,
                "tool": s.tool,
                "params": s.params,
                "result": s.result,
                "reasoning": s.reasoning,
                "tokens": s.tokens,
                "duration_ms": s.duration_ms,
            }
            for s in page_steps
        ],
    }
    return _envelope(data)