"""HTTP client for the backend.

Deliberately stdlib-only (`urllib`): the desktop app should start with the
system Python on a fresh machine, and a pomodoro client does not need an async
HTTP stack to call eight endpoints.
"""

from __future__ import annotations

import json
import urllib.error
import urllib.parse
import urllib.request
from typing import Any


class ApiError(RuntimeError):
    """A call failed. The message is meant to be shown in the UI."""

    def __init__(self, message: str, status: int = 0) -> None:
        super().__init__(message)
        self.status = status


class Api:
    def __init__(self, base_url: str, token: str = "", timeout: float = 10.0) -> None:
        self.base_url = base_url.rstrip("/")
        self.token = token
        self.timeout = timeout

    def configure(self, base_url: str, token: str) -> None:
        self.base_url = base_url.rstrip("/")
        self.token = token

    # ---- plumbing ----------------------------------------------------------

    def _request(self, method: str, path: str, payload: Any | None = None) -> Any:
        url = f"{self.base_url}{path}"
        data = None
        headers = {"Accept": "application/json"}
        if payload is not None:
            data = json.dumps(payload).encode("utf-8")
            headers["Content-Type"] = "application/json"
        if self.token:
            headers["X-API-Token"] = self.token

        request = urllib.request.Request(url, data=data, headers=headers, method=method)
        try:
            with urllib.request.urlopen(request, timeout=self.timeout) as response:
                body = response.read()
                return json.loads(body) if body else None
        except urllib.error.HTTPError as exc:
            detail = _detail(exc)
            if exc.code == 401:
                hint = (
                    "Set the API token in Settings → Backend."
                    if self.token
                    else "No API token configured — add it in Settings → Backend."
                )
                raise ApiError(f"{detail} {hint}", exc.code) from exc
            raise ApiError(detail, exc.code) from exc
        except (urllib.error.URLError, TimeoutError) as exc:
            raise ApiError(
                f"Cannot reach the backend at {self.base_url} ({exc}). "
                "Check the server URL in Settings → Backend, or is "
                "`docker compose up` running locally?"
            ) from exc
        except json.JSONDecodeError as exc:
            raise ApiError(f"The backend sent something that is not JSON: {exc}") from exc

    # ---- endpoints ---------------------------------------------------------

    def health(self) -> dict:
        return self._request("GET", "/api/health")

    def timer_state(self) -> dict:
        return self._request("GET", "/api/timer/state")

    def start(self, kind: str | None = None, task_id: int | None = None, minutes: int | None = None) -> dict:
        return self._request(
            "POST", "/api/timer/start", {"kind": kind, "task_id": task_id, "minutes": minutes}
        )

    def pause(self) -> dict:
        return self._request("POST", "/api/timer/pause", {})

    def resume(self) -> dict:
        return self._request("POST", "/api/timer/resume", {})

    def complete(self, auto_next: bool = True) -> dict:
        return self._request("POST", "/api/timer/complete", {"auto_next": auto_next})

    def abandon(self, reason: str | None = None) -> dict:
        return self._request("POST", "/api/timer/abandon", {"reason": reason})

    def extend(self, minutes: int = 5) -> dict:
        return self._request("POST", "/api/timer/extend", {"minutes": minutes})

    def interrupt(self) -> dict:
        return self._request("POST", "/api/timer/interrupt", {})

    def tasks(self) -> dict:
        """The list, read for one fact: which task is pinned.

        There is no Tasks page here any more — the list is the web app's job.
        `Controller._on_tasks` keeps the pinned id so that starting an interval
        from the tray attaches what you pinned this morning.
        """
        return self._request("GET", "/api/tasks")

    def refresh_tasks(self) -> dict:
        return self._request("POST", "/api/tasks/refresh", {})

    def blocker_policy(self) -> dict:
        return self._request("GET", "/api/blocker/policy")

    def report_block(self, kind: str, target: str, action: str = "blocked", details: str | None = None) -> dict:
        return self._request(
            "POST",
            "/api/blocker/events",
            {"kind": kind, "target": target, "action": action, "details": details},
        )

    def send_report(self) -> dict:
        return self._request("POST", "/api/reports/daily/send", {"force": True})

    def patch_settings(self, patch: dict) -> dict:
        return self._request("PUT", "/api/settings", patch)


def _detail(exc: urllib.error.HTTPError) -> str:
    try:
        body = json.loads(exc.read())
    except Exception:
        return f"{exc.code} {exc.reason}"
    detail = body.get("detail") if isinstance(body, dict) else None
    if isinstance(detail, str):
        return detail
    if isinstance(detail, list):
        return "; ".join(
            f"{'.'.join(str(part) for part in item.get('loc', [])[1:])}: {item.get('msg', '')}"
            for item in detail
        )
    return f"{exc.code} {exc.reason}"