"""Thread listing and detail endpoints (SPEC §9.1 Mail)."""

from __future__ import annotations

import uuid
from typing import Annotated

from fastapi import APIRouter, Depends, Query
from sqlalchemy import literal, select, tuple_
from sqlalchemy.ext.asyncio import AsyncSession

from app.api.cursors import decode_cursor, encode_cursor
from app.api.errors import raise_api_error
from app.api.schemas import (
    Address,
    MessageEnvelope,
    ThreadDetail,
    ThreadListOut,
    ThreadSummary,
)
from app.db import get_session
from app.identity.deps import CurrentUser
from app.models import Mailbox, Message, Thread, User

router = APIRouter(prefix="/threads", tags=["mail"])

DbSession = Annotated[AsyncSession, Depends(get_session)]


def _addresses(raw: list[dict[str, str]]) -> list[Address]:
    return [Address(name=a.get("name", ""), email=a.get("email", "")) for a in raw]


def _summary(thread: Thread) -> ThreadSummary:
    return ThreadSummary(
        id=thread.id,
        subject=thread.subject_norm or "(no subject)",
        snippet=thread.snippet,
        participants=_addresses(thread.participants),
        account_ids=list(thread.account_ids),
        message_count=thread.message_count,
        unread_count=thread.unread_count,
        has_attachments=thread.has_attachments,
        pinned=thread.pinned,
        last_message_at=thread.last_message_at,
    )


def _envelope(msg: Message) -> MessageEnvelope:
    return MessageEnvelope(
        id=msg.id,
        account_id=msg.account_id,
        mailbox_id=msg.mailbox_id,
        thread_id=msg.thread_id,
        subject=msg.subject,
        from_addr=_addresses(msg.from_addr),
        to_addr=_addresses(msg.to_addr),
        cc_addr=_addresses(msg.cc_addr),
        bcc_addr=_addresses(msg.bcc_addr),
        date=msg.date_hdr or msg.internal_date,
        flags=list(msg.flags),
        is_unread="\\Seen" not in msg.flags,
        is_starred="\\Flagged" in msg.flags,
        has_attachments=msg.has_attachments,
        has_remote_images=msg.has_remote_images,
        snippet=msg.snippet,
    )


@router.get("", response_model=ThreadListOut)
async def list_threads(
    user: CurrentUser,
    db: DbSession,
    view: str = Query("unified"),
    cursor: str | None = None,
    limit: int = Query(50, ge=1, le=200),
) -> ThreadListOut:
    stmt = select(Thread).where(Thread.user_id == user.id)

    if view.startswith("account:"):
        # A single account's inbox: threads with a message in THIS account's
        # inbox mailbox. Keeps the per-account view consistent with the unified
        # Inbox (archived/trashed/sent threads don't leak in).
        try:
            account_id = uuid.UUID(view.split(":", 1)[1])
        except ValueError:
            raise_api_error(400, "bad_view", "invalid account id in view")
        in_account_inbox = (
            select(Message.thread_id)
            .join(Mailbox, Mailbox.id == Message.mailbox_id)
            .where(
                Message.user_id == user.id,
                Message.account_id == account_id,
                Mailbox.special_use == "inbox",
            )
        )
        stmt = stmt.where(Thread.id.in_(in_account_inbox))
    elif view.startswith("folder:"):
        # Threads with at least one message in a mailbox of this special_use,
        # across all of the user's accounts (unified per-folder view).
        special = view.split(":", 1)[1]
        in_folder = (
            select(Message.thread_id)
            .join(Mailbox, Mailbox.id == Message.mailbox_id)
            .where(Message.user_id == user.id, Mailbox.special_use == special)
        )
        stmt = stmt.where(Thread.id.in_(in_folder))
    elif view != "unified":
        raise_api_error(400, "bad_view", "unsupported view")

    decoded = decode_cursor(cursor)
    if decoded is not None:
        cur_date, cur_id = decoded
        stmt = stmt.where(
            tuple_(Thread.last_message_at, Thread.id) < tuple_(literal(cur_date), literal(cur_id))
        )
    stmt = stmt.order_by(Thread.last_message_at.desc(), Thread.id.desc()).limit(limit + 1)

    threads = list(await db.scalars(stmt))
    has_more = len(threads) > limit
    threads = threads[:limit]
    next_cursor = (
        encode_cursor(threads[-1].last_message_at, threads[-1].id) if has_more and threads else None
    )
    return ThreadListOut(threads=[_summary(t) for t in threads], cursor=next_cursor)


async def _resolve_thread(db: AsyncSession, user: User, thread_id: uuid.UUID) -> Thread:
    thread = await db.scalar(
        select(Thread).where(Thread.id == thread_id, Thread.user_id == user.id)
    )
    if thread is None:
        raise_api_error(404, "not_found", "thread not found")
    return thread


@router.get("/{thread_id}", response_model=ThreadDetail)
async def get_thread(
    thread_id: uuid.UUID,
    user: CurrentUser,
    db: DbSession,
    sort: str = Query("asc"),
) -> ThreadDetail:
    thread = await _resolve_thread(db, user, thread_id)
    # Messages are always returned ASC (oldest first); the client reverses for
    # display per the requested order (invariant I-5 / §9.4).
    messages = list(
        await db.scalars(
            select(Message)
            .where(Message.thread_id == thread_id, Message.user_id == user.id)
            .order_by(Message.internal_date.asc(), Message.id.asc())
        )
    )
    order = "desc" if sort == "desc" else "asc"
    return ThreadDetail(
        id=thread.id,
        subject=thread.subject_norm or "(no subject)",
        order=order,
        pinned=thread.pinned,
        messages=[_envelope(m) for m in messages],
    )