"""Mission Control approval gate → GitHub required check.

This module maintains a GitHub Check Run (recommended) named:
- `mission-control/approval`

The check is intended to be added to GitHub ruleset required checks so PRs
cannot merge unless the corresponding Mission Control task has an approved
in-app approval.

Mapping:
- PR → Task: by `custom_field_values.github_pr_url` exact match.
- Task → Approval: any linked Approval rows with status in {pending, approved, rejected}.

Triggers (implemented via API hooks):
- approval created / resolved
- task github_pr_url updated

A periodic reconciliation job should call the sync functions as a safety net.
"""

from __future__ import annotations

import asyncio

from dataclasses import dataclass
from typing import Literal, cast
from uuid import UUID

from sqlmodel import col, select

from app.core.config import settings
from app.core.logging import get_logger
from app.db.session import async_session_maker
from app.models.approval_task_links import ApprovalTaskLink
from app.models.approvals import Approval
from app.models.boards import Board
from app.models.task_custom_fields import TaskCustomFieldDefinition, TaskCustomFieldValue
from app.models.tasks import Task
from app.services.github.client import (
    GitHubClientError,
    get_pull_request_head_sha,
    parse_pull_request_url,
    upsert_check_run,
)

if False:  # pragma: no cover
    from sqlmodel.ext.asyncio.session import AsyncSession

logger = get_logger(__name__)

CHECK_NAME = "mission-control/approval"

# Default action types that qualify as a "merge gate" approval.
# (Action types are free-form today; keep this conservative but configurable later.)
REQUIRED_ACTION_TYPES = {"mark_done", "mark_task_done"}


CheckOutcome = Literal["success", "pending", "rejected", "missing", "error", "multiple"]


@dataclass(frozen=True)
class ApprovalGateEvaluation:
    outcome: CheckOutcome
    task_ids: tuple[UUID, ...] = ()
    summary: str = ""


async def _board_org_id(session: AsyncSession, *, board_id: UUID) -> UUID | None:
    return (
        await session.exec(
            select(col(Board.organization_id)).where(col(Board.id) == board_id),
        )
    ).first()


async def _tasks_for_pr_url(
    session: AsyncSession,
    *,
    board_id: UUID,
    pr_url: str,
) -> list[Task]:
    """Return tasks whose `github_pr_url` custom field matches the PR URL.

    NOTE: custom-field values are stored as JSON, and cross-dialect equality
    semantics can be surprising. We therefore fetch candidate rows and perform a
    strict Python-side string match.
    """

    org_id = await _board_org_id(session, board_id=board_id)
    if org_id is None:
        return []

    normalized = pr_url.strip()
    if not normalized:
        return []

    statement = (
        select(Task, col(TaskCustomFieldValue.value))
        .join(TaskCustomFieldValue, col(TaskCustomFieldValue.task_id) == col(Task.id))
        .join(
            TaskCustomFieldDefinition,
            col(TaskCustomFieldDefinition.id)
            == col(TaskCustomFieldValue.task_custom_field_definition_id),
        )
        .where(col(Task.board_id) == board_id)
        .where(col(TaskCustomFieldDefinition.organization_id) == org_id)
        .where(col(TaskCustomFieldDefinition.field_key) == "github_pr_url")
        .order_by(col(Task.created_at).asc())
    )
    rows = list(await session.exec(statement))

    tasks: list[Task] = []
    for task, value in rows:
        if not isinstance(task, Task):
            continue
        if isinstance(value, str) and value.strip() == normalized:
            tasks.append(task)
    return tasks


async def _approval_rows_for_task(
    session: AsyncSession,
    *,
    board_id: UUID,
    task_id: UUID,
) -> list[Approval]:
    # Linked approvals (new style)
    linked_stmt = (
        select(Approval)
        .join(ApprovalTaskLink, col(ApprovalTaskLink.approval_id) == col(Approval.id))
        .where(col(Approval.board_id) == board_id)
        .where(col(ApprovalTaskLink.task_id) == task_id)
        .order_by(col(Approval.created_at).asc())
    )
    linked = list(await session.exec(linked_stmt))

    # Legacy approvals (Approval.task_id) not linked via ApprovalTaskLink
    legacy_stmt = (
        select(Approval)
        .where(col(Approval.board_id) == board_id)
        .where(col(Approval.task_id) == task_id)
        .order_by(col(Approval.created_at).asc())
    )
    legacy = list(await session.exec(legacy_stmt))

    # Merge unique by id
    by_id: dict[UUID, Approval] = {}
    for approval in [*linked, *legacy]:
        if isinstance(approval, Approval):
            by_id.setdefault(approval.id, approval)
    return list(by_id.values())


def _qualifies_for_gate(approval: Approval) -> bool:
    # If action types evolve, we can broaden this; for now keep it anchored.
    return approval.action_type in REQUIRED_ACTION_TYPES


async def evaluate_approval_gate_for_pr_url(
    session: AsyncSession,
    *,
    board_id: UUID,
    pr_url: str,
) -> ApprovalGateEvaluation:
    tasks = await _tasks_for_pr_url(session, board_id=board_id, pr_url=pr_url)
    if not tasks:
        return ApprovalGateEvaluation(
            outcome="missing",
            task_ids=(),
            summary=(
                "No Mission Control task is linked to this PR. Set the task custom field "
                "`github_pr_url` to this PR URL."
            ),
        )
    if len(tasks) > 1:
        return ApprovalGateEvaluation(
            outcome="multiple",
            task_ids=tuple(task.id for task in tasks),
            summary=(
                "Multiple Mission Control tasks are linked to this PR URL. "
                "Ensure exactly one task has `github_pr_url` set to this PR."
            ),
        )

    task = tasks[0]
    approvals = await _approval_rows_for_task(session, board_id=board_id, task_id=task.id)
    gate_approvals = [a for a in approvals if _qualifies_for_gate(a)]

    if not gate_approvals:
        return ApprovalGateEvaluation(
            outcome="missing",
            task_ids=(task.id,),
            summary=(
                "No qualifying approval found for this task. Create an approval request "
                f"(action_type in {sorted(REQUIRED_ACTION_TYPES)})."
            ),
        )

    statuses = [str(a.status) for a in gate_approvals]
    if any(s == "approved" for s in statuses):
        return ApprovalGateEvaluation(
            outcome="success",
            task_ids=(task.id,),
            summary="Approval is approved. Merge is permitted.",
        )
    if any(s == "rejected" for s in statuses):
        return ApprovalGateEvaluation(
            outcome="rejected",
            task_ids=(task.id,),
            summary="Approval was rejected. Merge is blocked until a new approval is granted.",
        )
    if any(s == "pending" for s in statuses):
        return ApprovalGateEvaluation(
            outcome="pending",
            task_ids=(task.id,),
            summary="Approval is pending. Merge is blocked until approved.",
        )

    return ApprovalGateEvaluation(
        outcome="error",
        task_ids=(task.id,),
        summary=f"Unexpected approval statuses: {sorted(set(statuses))}",
    )


async def sync_github_approval_check_for_pr_url(
    session: AsyncSession,
    *,
    board_id: UUID,
    pr_url: str,
) -> None:
    """Upsert the GitHub check run for a PR URL based on Mission Control approval state."""

    parsed = parse_pull_request_url(pr_url)
    if parsed is None:
        logger.warning(
            "github.approval_check.invalid_pr_url",
            extra={"board_id": str(board_id), "pr_url": pr_url},
        )
        return

    try:
        evaluation = await evaluate_approval_gate_for_pr_url(
            session,
            board_id=board_id,
            pr_url=pr_url,
        )

        head_sha = await get_pull_request_head_sha(parsed)

        title = "Mission Control approval gate"
        summary_lines = [
            f"PR: {parsed.url}",
            f"Board: {board_id}",
        ]
        if evaluation.task_ids:
            summary_lines.append("Task(s): " + ", ".join(str(tid) for tid in evaluation.task_ids))
        summary_lines.append("")
        summary_lines.append(evaluation.summary)

        if evaluation.outcome == "success":
            await upsert_check_run(
                owner=parsed.owner,
                repo=parsed.repo,
                head_sha=head_sha,
                check_name=CHECK_NAME,
                status="completed",
                conclusion="success",
                title=title,
                summary="\n".join(summary_lines),
            )
            return

        if evaluation.outcome == "pending":
            # Keep as in_progress to clearly signal it's waiting.
            await upsert_check_run(
                owner=parsed.owner,
                repo=parsed.repo,
                head_sha=head_sha,
                check_name=CHECK_NAME,
                status="in_progress",
                conclusion=None,
                title=title,
                summary="\n".join(summary_lines),
            )
            return

        # failure-like outcomes
        await upsert_check_run(
            owner=parsed.owner,
            repo=parsed.repo,
            head_sha=head_sha,
            check_name=CHECK_NAME,
            status="completed",
            conclusion="failure",
            title=title,
            summary="\n".join(summary_lines),
        )

    except GitHubClientError as exc:
        logger.warning(
            "github.approval_check.github_error",
            extra={"board_id": str(board_id), "pr_url": pr_url, "error": str(exc)},
        )
    except Exception as exc:
        logger.exception(
            "github.approval_check.unexpected",
            extra={"board_id": str(board_id), "pr_url": pr_url, "error": str(exc)},
        )


async def sync_github_approval_check_for_task_ids(
    session: AsyncSession,
    *,
    board_id: UUID,
    task_ids: list[UUID],
) -> None:
    """Sync approval checks for any tasks that have github_pr_url set.

    Used by approval hooks (one approval can link multiple tasks).
    """

    if not task_ids:
        return

    # Load custom-field values for these tasks and find github_pr_url.
    # We reuse the same join approach but filter by task ids.
    org_id = await _board_org_id(session, board_id=board_id)
    if org_id is None:
        return

    stmt = (
        select(col(TaskCustomFieldValue.task_id), col(TaskCustomFieldValue.value))
        .join(
            TaskCustomFieldDefinition,
            col(TaskCustomFieldDefinition.id)
            == col(TaskCustomFieldValue.task_custom_field_definition_id),
        )
        .where(col(TaskCustomFieldDefinition.organization_id) == org_id)
        .where(col(TaskCustomFieldDefinition.field_key) == "github_pr_url")
        .where(col(TaskCustomFieldValue.task_id).in_(task_ids))
    )
    rows = list(await session.exec(stmt))

    pr_urls: set[str] = set()
    for _task_id, value in rows:
        if isinstance(value, str) and value.strip():
            pr_urls.add(value.strip())

    for pr_url in sorted(pr_urls):
        await sync_github_approval_check_for_pr_url(session, board_id=board_id, pr_url=pr_url)


async def reconcile_github_approval_checks_for_board(
    session: AsyncSession,
    *,
    board_id: UUID,
) -> int:
    """Periodic reconciliation safety net.

    Returns number of distinct PR URLs processed.

    Intended to be run by a cron/worker periodically.
    """

    org_id = await _board_org_id(session, board_id=board_id)
    if org_id is None:
        return 0

    stmt = (
        select(col(TaskCustomFieldValue.value))
        .join(
            TaskCustomFieldDefinition,
            col(TaskCustomFieldDefinition.id)
            == col(TaskCustomFieldValue.task_custom_field_definition_id),
        )
        .join(Task, col(Task.id) == col(TaskCustomFieldValue.task_id))
        .where(col(Task.board_id) == board_id)
        .where(col(TaskCustomFieldDefinition.organization_id) == org_id)
        .where(col(TaskCustomFieldDefinition.field_key) == "github_pr_url")
    )
    raw_rows = list(await session.exec(stmt))
    rows = cast(list[tuple[object]], raw_rows)

    pr_urls: set[str] = set()
    for (value,) in rows:
        if isinstance(value, str) and value.strip():
            pr_urls.add(value.strip())

    pr_url_list = sorted(pr_urls)
    max_urls = settings.github_approval_check_reconcile_max_pr_urls
    if len(pr_url_list) > max_urls:
        logger.warning(
            "github.approval_check.reconcile.truncated_pr_urls",
            extra={"board_id": str(board_id), "count": len(pr_url_list), "max": max_urls},
        )
        pr_url_list = pr_url_list[:max_urls]

    sem = asyncio.Semaphore(settings.github_approval_check_reconcile_concurrency)

    async def _run(url: str) -> None:
        async with sem:
            await sync_github_approval_check_for_pr_url(
                session,
                board_id=board_id,
                pr_url=url,
            )

    # Process concurrently but bounded to avoid overwhelming GitHub.
    results = await asyncio.gather(*[_run(url) for url in pr_url_list], return_exceptions=True)
    for result in results:
        if isinstance(result, Exception):
            logger.exception(
                "github.approval_check.reconcile.pr_failed",
                extra={"board_id": str(board_id), "error": str(result)},
            )

    return len(pr_url_list)


async def reconcile_mission_control_approval_checks_for_all_boards() -> int:
    """Reconcile approval checks for every board.

    Returns total number of distinct PR URLs processed across boards.

    This is intentionally a safety net: the primary, low-latency updates happen on
    approval create/resolution and task github_pr_url updates.
    """

    async with async_session_maker() as session:
        raw_board_ids = list(
            await session.exec(
                select(col(Board.id)).order_by(col(Board.created_at).asc()),
            ),
        )
        board_ids = [value for value in raw_board_ids if isinstance(value, UUID)]
        processed = 0
        for board_id in board_ids:
            try:
                processed += await reconcile_github_approval_checks_for_board(
                    session,
                    board_id=board_id,
                )
            except Exception:
                logger.exception(
                    "github.approval_check.reconcile.board_failed",
                    extra={"board_id": str(board_id)},
                )
        return processed


def github_approval_check_enabled() -> bool:
    return bool((settings.github_token or "").strip())