"""任务相关的持久化操作与辅助函数。"""

from __future__ import annotations

from pathlib import Path
from typing import Any

import sqlite3

import storage


# ── 任务状态与状态机 ────────────────────────────────────────────────────────────

# 约定的任务状态枚举，避免在业务层随意写字符串
STATUS_QUEUED = "queued"
STATUS_RUNNING = "running"
STATUS_SUCCEEDED = "succeeded"
STATUS_FAILED = "failed"
STATUS_CANCELLED = "cancelled"

ALLOWED_STATUSES: set[str] = {
    STATUS_QUEUED,
    STATUS_RUNNING,
    STATUS_SUCCEEDED,
    STATUS_FAILED,
    STATUS_CANCELLED,
}


def row_to_job_dict(row: sqlite3.Row) -> dict[str, Any]:
    """将任务行转换为对外暴露的字典结构。"""
    job = dict(row)
    job["artifact_urls"] = {
        "mono": f"/api/jobs/{job['id']}/artifacts/mono"
        if job.get("mono_pdf_path")
        else None,
        "dual": f"/api/jobs/{job['id']}/artifacts/dual"
        if job.get("dual_pdf_path")
        else None,
        "glossary": f"/api/jobs/{job['id']}/artifacts/glossary"
        if job.get("glossary_path")
        else None,
    }
    return job


def update_job(job_id: str, **fields: Any) -> None:
    """更新任务记录指定字段。

    注意：业务代码应该优先通过 transition_job 做状态机驱动更新，
    直接调用本函数仅用于与状态无关的字段（例如 cancel_requested）。
    """
    if not fields:
        return
    fields["updated_at"] = storage.now_iso()
    set_clause = ", ".join(f"{k} = ?" for k in fields.keys())
    params = tuple(fields.values()) + (job_id,)
    storage.db_execute(f"UPDATE jobs SET {set_clause} WHERE id = ?", params)


def get_job_row(job_id: str) -> sqlite3.Row | None:
    """按 ID 获取任务原始行。"""
    return storage.db_fetchone("SELECT * FROM jobs WHERE id = ?", (job_id,))


def get_job_for_user(job_id: str, username: str) -> dict[str, Any] | None:
    """获取用户可见的任务，如果不存在或不属于该用户返回 None。"""
    row = storage.db_fetchone(
        "SELECT * FROM jobs WHERE id = ? AND username = ?",
        (job_id, username),
    )
    if row is None:
        return None
    return row_to_job_dict(row)


def get_jobs_for_user(username: str, limit: int) -> list[dict[str, Any]]:
    """列出用户的任务列表，按创建时间倒序。"""
    rows = storage.db_fetchall(
        """
        SELECT * FROM jobs
        WHERE username = ?
        ORDER BY created_at DESC
        LIMIT ?
        """,
        (username, limit),
    )
    return [row_to_job_dict(row) for row in rows]


def create_job_record(
    *,
    job_id: str,
    username: str,
    filename: str,
    input_path: Path,
    output_dir: Path,
    model: str,
    lang_in: str,
    lang_out: str,
) -> dict[str, Any]:
    """插入一条新任务并返回任务字典。"""
    now = storage.now_iso()
    storage.db_execute(
        """
        INSERT INTO jobs(
            id, username, filename, input_path, output_dir,
            status, progress, message, error,
            model, lang_in, lang_out,
            cancel_requested,
            created_at, updated_at
        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
        """,
        (
            job_id,
            username,
            filename,
            str(input_path),
            str(output_dir),
            "queued",
            0.0,
            "Queued",
            None,
            model,
            lang_in,
            lang_out,
            0,
            now,
            now,
        ),
    )
    row = storage.db_fetchone("SELECT * FROM jobs WHERE id = ?", (job_id,))
    if row is None:
        raise RuntimeError("Failed to fetch job after insert")
    return row_to_job_dict(row)


def resolve_artifact_path(raw_path: str | None, output_dir: Path) -> Path | None:
    """解析并校验任务产物路径，限制在 output_dir 内部。"""
    if not raw_path:
        return None
    path = Path(raw_path)
    if not path.is_absolute():
        path = (output_dir / path).resolve()
    else:
        path = path.resolve()

    if not path.exists():
        return None

    try:
        path.relative_to(output_dir)
    except ValueError:
        return None
    return path


def transition_job(job_id: str, event: str, **extra_fields: Any) -> dict[str, Any] | None:
    """基于事件驱动的任务状态迁移。

    这里只负责：
      * 校验当前状态是否允许执行给定事件
      * 决定目标状态（如果有）
      * 写入数据库
      * 返回更新后的任务字典（用于推送给前端）

    状态枚举固定为 queued/running/succeeded/failed/cancelled，避免状态空间爆炸。
    """
    row = get_job_row(job_id)
    if row is None:
        return None

    current_status = row["status"]
    if current_status not in ALLOWED_STATUSES:
        # 非法状态一律拒绝迁移，由调用方记录日志
        return None

    # 简单的事件 -> 允许来源状态集合、目标状态映射
    # 对于 progress 这类事件，目标状态为 None，只更新进度等字段。
    transitions: dict[str, dict[str, Any]] = {
        "start": {
            "from": {STATUS_QUEUED},
            "to": STATUS_RUNNING,
        },
        "progress": {
            "from": {STATUS_RUNNING},
            "to": None,
        },
        "finish_ok": {
            "from": {STATUS_RUNNING},
            "to": STATUS_SUCCEEDED,
        },
        "finish_error": {
            "from": {STATUS_QUEUED, STATUS_RUNNING},
            "to": STATUS_FAILED,
        },
        "cancel_before_start": {
            "from": {STATUS_QUEUED},
            "to": STATUS_CANCELLED,
        },
        "cancel_running": {
            "from": {STATUS_RUNNING},
            "to": STATUS_CANCELLED,
        },
        # 预留重启失败事件，当前在 gateway 中直接 SQL 处理，不走这里
        "restart_fail": {
            "from": {STATUS_RUNNING},
            "to": STATUS_FAILED,
        },
    }

    cfg = transitions.get(event)
    if cfg is None:
        return None

    if current_status not in cfg["from"]:
        return None

    fields: dict[str, Any] = dict(extra_fields)
    target_status = cfg["to"]
    if target_status is not None:
        fields["status"] = target_status

    update_job(job_id, **fields)
    new_row = get_job_row(job_id)
    if new_row is None:
        return None
    return row_to_job_dict(new_row)