"""Todoist as a todo source.

A personal API token sent as a Bearer token — no OAuth dance. jira-helper asks
Todoist's own `overdue | today` filter so Todoist's timezone and recurrence
rules decide what is due; here the default is *every* open task (you need
something to point the timer at), with the filter still available as a setting
for people who want the narrower list.
"""

from __future__ import annotations

from collections.abc import Iterator
from datetime import date
from typing import Any

import httpx

from app.settings_schema import TodoistSourceSettings
from app.sources.base import SourceError, TodoItem

_API_BASE = "https://api.todoist.com/api/v1"
_TASK_URL = "https://app.todoist.com/app/task/{task_id}"
_PAGE_SIZE = 200

# Todoist stores priority upside down from how its apps label it: 4 is "p1".
_PRIORITY_LABELS = {4: "p1", 3: "p2", 2: "p3"}


class TodoistSource:
    name = "todoist"

    def __init__(self, config: TodoistSourceSettings, *, timeout: int = 30) -> None:
        if not config.api_token:
            raise SourceError("Todoist needs an API token (Settings → Integrations).")
        self._config = config
        self._client = httpx.Client(
            base_url=_API_BASE,
            headers={
                "Accept": "application/json",
                "Authorization": f"Bearer {config.api_token}",
            },
            timeout=timeout,
        )

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

    def _get(self, path: str, params: dict[str, Any]) -> dict[str, Any]:
        try:
            resp = self._client.get(path, params=params)
        except httpx.HTTPError as exc:
            raise SourceError(f"Todoist is unreachable: {exc}") from exc
        if resp.status_code in (401, 403):
            raise SourceError("Todoist rejected the API token.")
        if not resp.is_success:
            raise SourceError(f"Todoist GET {path} -> {resp.status_code}: {resp.text[:300]}")
        return resp.json() or {}

    def _paginate(self, path: str, params: dict[str, Any]) -> Iterator[dict[str, Any]]:
        params = dict(params)
        while True:
            data = self._get(path, params)
            yield from data.get("results", [])
            cursor = data.get("next_cursor")
            if not cursor:
                return
            params["cursor"] = cursor

    def _projects(self) -> dict[str, str]:
        return {
            project["id"]: project.get("name") or "(untitled project)"
            for project in self._paginate("/projects", {"limit": _PAGE_SIZE})
            if project.get("id")
        }

    def _selected(self, project_id: str, project_name: str) -> bool:
        if not self._config.projects:
            return True
        wanted = set(self._config.projects)
        return bool(wanted & {project_id, project_name})

    # ---- source API --------------------------------------------------------

    def fetch(self) -> list[TodoItem]:
        projects = self._projects()
        query = self._config.filter_query.strip()
        if query:
            raw_tasks = self._paginate("/tasks/filter", {"query": query, "limit": _PAGE_SIZE})
        else:
            raw_tasks = self._paginate("/tasks", {"limit": _PAGE_SIZE})

        items: list[TodoItem] = []
        for raw in raw_tasks:
            if raw.get("checked") or raw.get("is_deleted"):
                continue
            project_id = raw.get("project_id") or ""
            project_name = projects.get(project_id, "(unknown project)")
            if not self._selected(project_id, project_name):
                continue
            task_id = str(raw.get("id") or "")
            due = raw.get("due") or {}
            items.append(
                TodoItem(
                    source=self.name,
                    external_id=task_id,
                    title=(raw.get("content") or "").strip() or "(no content)",
                    description=(raw.get("description") or "").strip() or None,
                    url=_TASK_URL.format(task_id=task_id) if task_id else None,
                    project=project_name,
                    priority=_PRIORITY_LABELS.get(raw.get("priority")),
                    due_date=_parse_due(due),
                    labels=list(raw.get("labels") or []),
                    raw={"recurring": bool(due.get("is_recurring"))},
                )
            )
        return items

    def check(self) -> str:
        projects = self._projects()
        return f"{len(projects)} Todoist project(s) visible"

    def close(self) -> None:
        self._client.close()


def _parse_due(due: Any) -> date | None:
    if not isinstance(due, dict):
        return None
    raw = due.get("date")
    if not raw:
        return None
    try:
        return date.fromisoformat(str(raw)[:10])
    except ValueError:
        return None