import json
from copy import deepcopy
from pathlib import Path
from typing import Any

from app.config import settings


class CourseService:
    def __init__(self, data_dir: Path | None = None) -> None:
        self.data_dir = data_dir or settings.data_dir

    def _read_json(self, path: Path) -> dict[str, Any]:
        with path.open(encoding="utf-8") as f:
            return json.load(f)

    def static_url(self, server_rel_path: str, base_url: str) -> str:
        rel = server_rel_path.replace("\\", "/").lstrip("/")
        return f"{base_url.rstrip('/')}/static/{rel}"

    def _resolve_media_url(self, path: str, base_url: str) -> str:
        if path.startswith("http://") or path.startswith("https://"):
            return path
        return self.static_url(path, base_url)

    def _resolve_asset_urls(self, asset: dict[str, Any], base_url: str) -> dict[str, Any]:
        resolved = dict(asset)
        if resolved.get("url"):
            resolved["url"] = self._resolve_media_url(resolved["url"], base_url)
        if resolved.get("cover_url"):
            resolved["cover_url"] = self._resolve_media_url(resolved["cover_url"], base_url)
        return resolved

    def get_course_index(self) -> dict[str, Any]:
        return self._read_json(self.data_dir / "courses" / "index.json")

    def get_course(self, course_id: str) -> dict[str, Any]:
        index = self.get_course_index()
        for item in index.get("courses", []):
            if item["course_id"] == course_id:
                config_path = self.data_dir / item["config"]
                return self._read_json(config_path)
        raise FileNotFoundError(f"Course not found: {course_id}")

    def get_tasklist(self) -> dict[str, Any]:
        return self._read_json(self.data_dir / "tasklist.json")

    def get_course_task(self, course_id: str) -> dict[str, Any]:
        path = self.data_dir / "courses" / course_id / "courseTask.json"
        if not path.exists():
            raise FileNotFoundError(f"Course task not found: {course_id}")
        return self._read_json(path)

    def build_course_task_sync_payload(self, course_id: str, base_url: str) -> dict[str, Any]:
        task = deepcopy(self.get_course_task(course_id))
        assets = task.get("assets", [])
        task["assets"] = [self._resolve_asset_urls(asset, base_url) for asset in assets]
        return task

    def build_base_course_sync_payloads(self, base_url: str) -> list[dict[str, Any]]:
        index = self.get_course_index()
        payloads: list[dict[str, Any]] = []
        for item in index.get("courses", []):
            course_id = item["course_id"]
            task_path = self.data_dir / "courses" / course_id / "courseTask.json"
            if task_path.exists():
                payloads.append(self.build_course_task_sync_payload(course_id, base_url))
        return payloads

    def build_manifest_assets(self, course_id: str, base_url: str) -> list[dict[str, Any]]:
        task = self.get_course_task(course_id)
        return [self._resolve_asset_urls(asset, base_url) for asset in task.get("assets", [])]