"""Sessions API — state retrieval, orchestrator iterate stream, world_builder/editor streams, retry/rollback."""

from __future__ import annotations

import json
import urllib.parse
import uuid
from datetime import datetime, timezone

from fastapi import APIRouter, Depends, HTTPException, Query, Response, status
from fastapi.responses import StreamingResponse
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.api.deps import get_current_user, get_settings_dict
from app.core.llm import LlmClient, MockLlmClient
from app.core.logging import get_logger
from app.db import get_db
from app.engine.game_master import run_iteration
from app.engine.sse import SseEmitter
from app.engine.world_builder import run_world_builder
from app.engine.world_editor import run_world_editor
from app.models import Entity, Step, World, WorldPreset
from app.schemas import AnswerRequest, IterateRequest

_logger = get_logger(__name__)

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


def _llm_factory(settings: dict) -> LlmClient | MockLlmClient:
    api_url = settings.get("llm.api_url", "")
    if not api_url:
        return MockLlmClient()
    return LlmClient.from_settings(settings)


async def _load_world(db: AsyncSession, world_id: uuid.UUID, user) -> World:
    world = (
        await db.execute(select(World).where(World.id == world_id))
    ).scalar_one_or_none()
    if world is None:
        raise HTTPException(404, "not_found")
    if world.owner_id != user.id and not user.is_admin:
        raise HTTPException(403, "not_owner")
    return world


# --------------------------------------------------------------------------- #
# State retrieval
# --------------------------------------------------------------------------- #
@router.get("/worlds/{world_id}/state")
async def get_state(
    world_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
) -> dict:
    """Return current session state for the play page."""
    world = await _load_world(db, world_id, user)
    recent = (
        await db.execute(
            select(Step)
            .where(Step.world_id == world.id, Step.deleted_at.is_(None))
            .order_by(Step.sequence_number.desc())
            .limit(10)
        )
    ).scalars().all()
    recent_steps = [
        {
            "id": str(s.id), "sequence_number": s.sequence_number,
            "player_action": s.player_action, "scene_text": s.scene_text,
            "suggested_actions": s.suggested_actions, "created_at": s.created_at.isoformat(),
        }
        for s in reversed(recent)
    ]
    next_actions = recent_steps[-1]["suggested_actions"] if recent_steps else []
    if world.intro_scene and not recent_steps:
        next_actions = []
    from app.core.time_utils import format_time_human
    return {
        "world": {
            "id": str(world.id), "name": world.name,
            "current_time": world.current_time,
            "current_time_human": format_time_human(world.current_time, world.language),
            "language": world.language, "intro_scene": world.intro_scene,
            "status": world.status,
        },
        "environment": world.environment,
        "recent_steps": recent_steps,
        "next_actions": next_actions,
    }


# --------------------------------------------------------------------------- #
# World builder stream (SSE)
# --------------------------------------------------------------------------- #
@router.get("/worlds/{world_id}/builder/stream")
async def builder_stream(
    world_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
    settings: dict = Depends(get_settings_dict),
) -> StreamingResponse:
    world = await _load_world(db, world_id, user)
    preset: WorldPreset | None = None
    if world.preset_id:
        preset = (
            await db.execute(select(WorldPreset).where(WorldPreset.id == world.preset_id))
        ).scalar_one_or_none()
    emitter = SseEmitter()
    player_name = (world.environment or {}).get("player", {}).get("name", "Hero")
    notes = world.description
    llm = _llm_factory(settings)

    async def run_bg():
        async with _session_scope() as bg_db:
            # Reload world in this session
            bg_world = (
                await bg_db.execute(select(World).where(World.id == world.id))
            ).scalar_one()
            await run_world_builder(
                db=bg_db, world=bg_world, player_name=player_name, notes=notes,
                llm=llm, sse=emitter, preset=preset,
            )

    import asyncio

    task = asyncio.create_task(run_bg())

    async def gen():
        try:
            async for evt in emitter.stream():
                yield _format_sse(evt)
        finally:
            await task

    return StreamingResponse(
        gen(), media_type="text/event-stream",
        headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"},
    )


# --------------------------------------------------------------------------- #
# World editor stream (SSE)
# --------------------------------------------------------------------------- #
@router.get("/worlds/{world_id}/editor/stream")
async def editor_stream(
    world_id: uuid.UUID,
    instruction: str = Query(...),
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
    settings: dict = Depends(get_settings_dict),
) -> StreamingResponse:
    world = await _load_world(db, world_id, user)
    emitter = SseEmitter()
    llm = _llm_factory(settings)

    async def run_bg():
        async with _session_scope() as bg_db:
            bg_world = (
                await bg_db.execute(select(World).where(World.id == world.id))
            ).scalar_one()
            await run_world_editor(
                db=bg_db, world=bg_world, instruction=instruction, llm=llm, sse=emitter,
            )

    import asyncio

    task = asyncio.create_task(run_bg())

    async def gen():
        try:
            async for evt in emitter.stream():
                yield _format_sse(evt)
        finally:
            await task

    return StreamingResponse(
        gen(), media_type="text/event-stream",
        headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"},
    )


# --------------------------------------------------------------------------- #
# Orchestrator iterate
# --------------------------------------------------------------------------- #
@router.post("/worlds/{world_id}/iterate", response_model=dict, status_code=status.HTTP_202_ACCEPTED)
async def iterate(
    world_id: uuid.UUID,
    body: IterateRequest,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
    settings: dict = Depends(get_settings_dict),
) -> dict:
    world = await _load_world(db, world_id, user)
    if world.status != "ready":
        raise HTTPException(422, "world_not_ready")
    # Compute next sequence number
    last_seq = (
        await db.execute(
            select(Step.sequence_number)
            .where(Step.world_id == world.id, Step.deleted_at.is_(None))
            .order_by(Step.sequence_number.desc())
            .limit(1)
        )
    ).scalar_one_or_none()
    next_seq = (last_seq or 0) + 1
    step = Step(
        world_id=world.id,
        sequence_number=next_seq,
        player_action=body.action,
        status="pending",
    )
    db.add(step)
    await db.commit()
    await db.refresh(step)
    return {
        "stream_url": f"/api/sessions/worlds/{world.id}/iterate/stream?step_id={step.id}",
        "step_id": str(step.id),
    }


@router.get("/worlds/{world_id}/iterate/stream")
async def iterate_stream(
    world_id: uuid.UUID,
    step_id: uuid.UUID = Query(...),
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
    settings: dict = Depends(get_settings_dict),
) -> StreamingResponse:
    world = await _load_world(db, world_id, user)
    step = (
        await db.execute(select(Step).where(Step.id == step_id, Step.world_id == world.id))
    ).scalar_one_or_none()
    if step is None:
        raise HTTPException(404, "step not found")
    emitter = SseEmitter()
    llm = _llm_factory(settings)

    async def run_bg():
        async with _session_scope() as bg_db:
            bg_world = (
                await bg_db.execute(select(World).where(World.id == world.id))
            ).scalar_one()
            bg_step = (
                await bg_db.execute(select(Step).where(Step.id == step.id))
            ).scalar_one()
            await run_iteration(db=bg_db, world=bg_world, step=bg_step, llm=llm, sse=emitter)

    import asyncio

    task = asyncio.create_task(run_bg())

    async def gen():
        try:
            async for evt in emitter.stream():
                yield _format_sse(evt)
        finally:
            await task

    return StreamingResponse(
        gen(), media_type="text/event-stream",
        headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"},
    )


# --------------------------------------------------------------------------- #
# World editor: accept/reject proposed changes, answer clarifications
# --------------------------------------------------------------------------- #
@router.post("/worlds/{world_id}/apply")
async def apply_proposed_changes(
    world_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
) -> dict:
    """Accept proposed changes from the world_editor stream."""
    from app.engine.world_editor import submit_propose_changes_answer

    world = await _load_world(db, world_id, user)
    ok = submit_propose_changes_answer(world.id, True)
    if not ok:
        raise HTTPException(409, "no_pending_changes")
    return {"ok": True}


@router.post("/worlds/{world_id}/discard")
async def discard_proposed_changes(
    world_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
) -> dict:
    """Reject proposed changes from the world_editor stream."""
    from app.engine.world_editor import submit_propose_changes_answer

    world = await _load_world(db, world_id, user)
    ok = submit_propose_changes_answer(world.id, False)
    if not ok:
        raise HTTPException(409, "no_pending_changes")
    return {"ok": True}


@router.post("/worlds/{world_id}/answer")
async def answer_clarification(
    world_id: uuid.UUID,
    body: AnswerRequest,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
) -> dict:
    """Answer an ask_user clarification from the world_editor stream."""
    from app.engine.world_editor import submit_clarification_answer

    world = await _load_world(db, world_id, user)
    ok = submit_clarification_answer(world.id, body.text)
    if not ok:
        raise HTTPException(409, "no_pending_clarification")
    return {"ok": True}


# --------------------------------------------------------------------------- #
# Generate / re-generate intro scene (for worlds stuck in draft)
# --------------------------------------------------------------------------- #
@router.post("/worlds/{world_id}/generate-intro", response_model=dict, status_code=status.HTTP_202_ACCEPTED)
async def generate_intro(
    world_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
    settings: dict = Depends(get_settings_dict),
) -> dict:
    """Re-generate the intro scene for a draft world.

    This runs the intro_scene stage of the world_builder flow without
    regenerating schemas/entities. Useful when the world was created from
    a preset (which provides schemas + entities) but the intro scene
    generation failed.
    """
    world = await _load_world(db, world_id, user)
    if world.status == "archived":
        raise HTTPException(422, "world_archived")
    return {
        "stream_url": f"/api/sessions/worlds/{world.id}/intro/stream",
    }


@router.get("/worlds/{world_id}/intro/stream")
async def intro_stream(
    world_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
    settings: dict = Depends(get_settings_dict),
) -> StreamingResponse:
    world = await _load_world(db, world_id, user)
    emitter = SseEmitter()
    llm = _llm_factory(settings)

    async def run_bg():
        async with _session_scope() as bg_db:
            from sqlalchemy import select as sa_select

            from app.engine.world_builder import _run_tool_loop, _strip_code_fence
            from app.engine.tools.base import ToolContext, get_registry
            from app.models import Entity
            from app.prompts.registry import get_prompt
            from app.core.time_utils import advance_time, summarize_schemas
            import json as _json

            bg_world = (
                await bg_db.execute(sa_select(World).where(World.id == world.id))
            ).scalar_one()
            try:
                await emitter.emit("step", {"step": "generating_intro", "message": "Generating intro scene..."})
                entities = (
                    await bg_db.execute(
                        sa_select(Entity).where(
                            Entity.world_id == bg_world.id, Entity.deleted_at.is_(None)
                        )
                    )
                ).scalars().all()
                entities_summary = "\n".join(
                    f"- {e.entity_type}: {e.name}" for e in entities[:20]
                ) or "(no entities)"
                intro_prompt = get_prompt("intro_scene", "en").format(
                    world_name=bg_world.name,
                    world_description=bg_world.description or "",
                    language=bg_world.language,
                    current_time=bg_world.current_time,
                    environment_json=_json.dumps(bg_world.environment or {}, ensure_ascii=False, indent=2),
                    plot_rails_json=_json.dumps(bg_world.plot_rails or {}, ensure_ascii=False, indent=2),
                    entities_summary=entities_summary,
                )
                scene_result = await _run_tool_loop(
                    db=bg_db, world=bg_world, llm=llm, sse=emitter,
                    stage="intro_scene",
                    system_prompt=intro_prompt,
                    terminal_tool="submit_step",
                    max_substeps=3,
                    settings={},
                )
                scene_text = ""
                delta_time = "hours_1"
                if scene_result and scene_result.get("ok"):
                    scene_text = scene_result.get("data", {}).get("scene_text", "")
                    delta_time = scene_result.get("data", {}).get("delta_time", "hours_1")
                bg_world.intro_scene = scene_text
                bg_world.current_time = advance_time(bg_world.current_time, delta_time, bg_world.time_schema)
                bg_world.status = "ready"
                await bg_db.commit()
                await emitter.emit("intro_scene_complete", {
                    "text": scene_text, "delta_time": delta_time,
                    "current_time": bg_world.current_time,
                })
                await emitter.done({"world_id": str(bg_world.id), "status": "ready"})
            except Exception as e:
                await emitter.error("internal_error", str(e))

    import asyncio

    task = asyncio.create_task(run_bg())

    async def gen():
        try:
            async for evt in emitter.stream():
                yield _format_sse(evt)
        finally:
            await task

    return StreamingResponse(
        gen(), media_type="text/event-stream",
        headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"},
    )


# --------------------------------------------------------------------------- #
# Retry / rollback
# --------------------------------------------------------------------------- #
@router.post("/worlds/{world_id}/retry", response_model=dict)
async def retry_last(
    world_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
) -> dict:
    """Soft-delete the last step and create a new one with the same action."""
    world = await _load_world(db, world_id, user)
    last = (
        await db.execute(
            select(Step)
            .where(Step.world_id == world.id, Step.deleted_at.is_(None))
            .order_by(Step.sequence_number.desc())
            .limit(1)
        )
    ).scalar_one_or_none()
    if last is None:
        raise HTTPException(404, "no_step_to_retry")
    last.deleted_at = datetime.now(timezone.utc)
    new_step = Step(
        world_id=world.id,
        sequence_number=last.sequence_number + 1,
        player_action=last.player_action,
        status="pending",
    )
    db.add(new_step)
    await db.commit()
    await db.refresh(new_step)
    return {
        "step_id": str(new_step.id),
        "stream_url": f"/api/sessions/worlds/{world.id}/iterate/stream?step_id={new_step.id}",
    }


@router.post("/worlds/{world_id}/rollback", status_code=status.HTTP_204_NO_CONTENT, response_class=Response)
async def rollback_last(
    world_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
) -> Response:
    """Soft-delete the last step."""
    world = await _load_world(db, world_id, user)
    last = (
        await db.execute(
            select(Step)
            .where(Step.world_id == world.id, Step.deleted_at.is_(None))
            .order_by(Step.sequence_number.desc())
            .limit(1)
        )
    ).scalar_one_or_none()
    if last is None:
        raise HTTPException(404, "no_step_to_rollback")
    last.deleted_at = datetime.now(timezone.utc)
    await db.commit()
    return Response(status_code=status.HTTP_204_NO_CONTENT)


# --------------------------------------------------------------------------- #
# Helpers
# --------------------------------------------------------------------------- #
def _format_sse(evt: dict[str, str]) -> str:
    """Format an SSE event dict into the wire format."""
    lines = []
    if "id" in evt:
        lines.append(f"id: {evt['id']}")
    if "event" in evt:
        lines.append(f"event: {evt['event']}")
    if "data" in evt:
        # Split multi-line data
        for chunk in evt["data"].split("\n"):
            lines.append(f"data: {chunk}")
    lines.append("")
    lines.append("")
    return "\n".join(lines)


from contextlib import asynccontextmanager


@asynccontextmanager
async def _session_scope():
    """Open a fresh DB session for the background task.

    Must be used as:  async with _session_scope() as bg_db: ...
    The @asynccontextmanager decorator is required — without it, an
    `async def` with `yield` returns an async generator, which does NOT
    support `async with`.
    """
    from app.db import get_sessionmaker

    sm = get_sessionmaker()
    async with sm() as s:
        yield s