import { Tool } from "@modelcontextprotocol/sdk/types.js";
import { NextcloudClient } from "../client.js";
import { ToolModule } from "./index.js";
import { ToolResponse } from "../types.js";
import {
  CalendarInfo,
  buildCalendarDiscoveryPropfindBody,
  buildCalendarEventsReportBody,
  dedupeEvents,
  formatICalDate,
  formatICalDateTimeUtc,
  getEventSortTimestamp,
  parseCalendarsFromPROPFIND,
  parseEventsFromCalDAV,
  parseISODateOnlyLocalMidnight,
  resolveCalendarSelectors,
  stripEventInternalFields,
} from "../caldav.js";
import { format } from "date-fns";
import { escapeICalText, generateUUID as generateUID } from "../utils.js";

export const calendarToolModule: ToolModule = {
  definitions: [
    {
      name: "list_calendars",
      description: "List available Nextcloud CalDAV calendars with href and supported components",
      inputSchema: { type: "object", properties: {} },
    },
    {
      name: "get_calendar_events",
      description: "Retrieve calendar events from Nextcloud. Can specify date range.",
      inputSchema: {
        type: "object",
        properties: {
          startDate: {
            type: "string",
            description: "Start date in ISO format (YYYY-MM-DD). Defaults to today.",
          },
          endDate: {
            type: "string",
            description: "End date in ISO format (YYYY-MM-DD). Defaults to 30 days from start.",
          },
          calendar: {
            type: "string",
            description: "Calendar selector by display name or href path (optional)",
          },
          calendars: {
            type: "array",
            items: { type: "string" },
            description: "List of calendar selectors by display name or href path (optional)",
          },
          includeAllCalendars: {
            type: "boolean",
            description: "When true and no calendar selectors are provided, query all VEVENT calendars",
            default: true,
          },
          limit: {
            type: "number",
            description: "Maximum number of events to return",
            default: 50,
          },
        },
      },
    },
    {
      name: "create_calendar_event",
      description: "Create a new calendar event in Nextcloud",
      inputSchema: {
        type: "object",
        properties: {
          summary: { type: "string", description: "Event title/summary" },
          description: { type: "string", description: "Event description (optional)" },
          allDay: {
            type: "boolean",
            description: "Create an all-day event. Use startDate/endDate when true.",
            default: false,
          },
          startDateTime: {
            type: "string",
            description: "Start date/time in ISO format (YYYY-MM-DDTHH:mm:ss). Required for timed events.",
          },
          endDateTime: {
            type: "string",
            description: "End date/time in ISO format (YYYY-MM-DDTHH:mm:ss). Required for timed events.",
          },
          startDate: {
            type: "string",
            description: "All-day start date in YYYY-MM-DD (or YYYY/MM/DD). Required when allDay=true.",
          },
          endDate: {
            type: "string",
            description: "All-day inclusive end date in YYYY-MM-DD (or YYYY/MM/DD). Optional; defaults to startDate.",
          },
          reminderMinutesBefore: {
            type: "number",
            description: "Reminder trigger relative to event start, in minutes before start (optional).",
          },
          reminderDateTime: {
            type: "string",
            description: "Absolute reminder timestamp in ISO format (optional, mutually exclusive with reminderMinutesBefore).",
          },
          reminderDescription: {
            type: "string",
            description: "Reminder text shown to the user (optional).",
          },
          reminderAction: {
            type: "string",
            description: "Alarm action type (optional, defaults to DISPLAY).",
          },
          location: {
            type: "string",
            description: "Event location (optional)",
          },
        },
        required: ["summary"],
      },
    },
  ],

  async handler(name, args, client): Promise<ToolResponse> {
    switch (name) {
      case "list_calendars":
        return listCalendars(client);
      case "get_calendar_events":
        return getCalendarEvents(args, client);
      case "create_calendar_event":
        return createCalendarEvent(args, client);
      default:
        throw new Error(`Unknown calendar tool: ${name}`);
    }
  },
};

// --- Implementation ---

async function listCalendars(client: NextcloudClient): Promise<ToolResponse> {
  const calendars = await discoverCalendars(client);
  return {
    content: [{ type: "text", text: JSON.stringify(calendars, null, 2) }],
  };
}

async function getCalendarEvents(args: any, client: NextcloudClient): Promise<ToolResponse> {
  const startDate = args.startDate || format(new Date(), "yyyy-MM-dd");
  const endDate =
    args.endDate ||
    format(new Date(Date.now() + 30 * 24 * 60 * 60 * 1000), "yyyy-MM-dd");
  const limit = args.limit || 50;
  const includeAllCalendars = args.includeAllCalendars !== false;
  const selectorList: string[] = [];
  if (typeof args.calendar === "string" && args.calendar.trim()) {
    selectorList.push(args.calendar.trim());
  }
  if (Array.isArray(args.calendars)) {
    for (const selector of args.calendars) {
      if (typeof selector === "string" && selector.trim()) {
        selectorList.push(selector.trim());
      }
    }
  }

  const startLocal = parseISODateOnlyLocalMidnight(startDate, "startDate");
  const endLocal = parseISODateOnlyLocalMidnight(endDate, "endDate");

  if (endLocal < startLocal) {
    throw new Error("endDate must be on or after startDate");
  }

  try {
    const calendars = await discoverCalendars(client);
    const veventCalendars = calendars.filter((calendar) =>
      calendar.components.includes("VEVENT")
    );

    if (veventCalendars.length === 0) {
      return {
        content: [{ type: "text", text: JSON.stringify([], null, 2) }],
      };
    }

    let targetCalendars: CalendarInfo[] = [];
    if (selectorList.length > 0) {
      targetCalendars = resolveCalendarSelectors(selectorList, calendars);
    } else if (includeAllCalendars) {
      targetCalendars = veventCalendars;
    } else {
      const personalCalendar = veventCalendars.find(
        (calendar) => calendar.name.toLowerCase() === "personal"
      );
      targetCalendars = personalCalendar ? [personalCalendar] : [veventCalendars[0]];
    }

    const requestBody = buildCalendarEventsReportBody(startLocal, endLocal);

    const mergedEvents: any[] = [];
    const requestErrors: string[] = [];

    for (const calendar of targetCalendars) {
      try {
        debugLog(client, `Querying calendar href: ${calendar.href}`);
        debugLog(client, `REPORT body for ${calendar.href}:\n${requestBody}`);

        const response = await client.report(calendar.href, requestBody, "1");

        debugLog(
          client,
          `REPORT response for ${calendar.href}: status=200 body-preview=${response.slice(0, 500)}`
        );

        const events = parseEventsFromCalDAV(
          response,
          calendar.href,
          (message) => debugLog(client, message)
        ).map((event) => ({
          ...event,
          calendarName: calendar.name,
          calendarHref: calendar.href,
        }));
        mergedEvents.push(...events);
      } catch (error: any) {
        requestErrors.push(`${calendar.href}: ${error.message}`);
        debugLog(client, `Calendar query failed for ${calendar.href}: ${error.message}`);
      }
    }

    if (mergedEvents.length === 0 && requestErrors.length > 0) {
      throw new Error(
        `Failed to fetch calendar events from selected calendars: ${requestErrors.join("; ")}`
      );
    }

    const deduped = dedupeEvents(mergedEvents);
    deduped.sort((a, b) => getEventSortTimestamp(a) - getEventSortTimestamp(b));
    const events = deduped.slice(0, limit).map((event) => stripEventInternalFields(event));

    return {
      content: [{ type: "text", text: JSON.stringify(events, null, 2) }],
    };
  } catch (error: any) {
    throw new Error(`Failed to fetch calendar events: ${error.message}`);
  }
}

async function createCalendarEvent(args: any, client: NextcloudClient): Promise<ToolResponse> {
  const {
    summary,
    description,
    location,
    allDay,
    startDateTime,
    endDateTime,
    startDate,
    endDate,
    reminderMinutesBefore,
    reminderDateTime,
    reminderDescription,
    reminderAction,
  } = args;
  const uid = generateUID();
  const isAllDay = allDay === true;

  let dtStartLine = "";
  let dtEndLine = "";

  if (isAllDay) {
    if (!startDate) {
      throw new Error("startDate is required when allDay=true");
    }
    const start = parseISODateOnlyLocalMidnight(startDate, "startDate");
    const endInclusive = parseISODateOnlyLocalMidnight(endDate || startDate, "endDate");
    if (endInclusive < start) {
      throw new Error("endDate must be on or after startDate");
    }

    const endExclusive = new Date(endInclusive.getTime());
    endExclusive.setDate(endExclusive.getDate() + 1);

    dtStartLine = `DTSTART;VALUE=DATE:${formatICalDate(start)}`;
    dtEndLine = `DTEND;VALUE=DATE:${formatICalDate(endExclusive)}`;
  } else {
    if (!startDateTime || !endDateTime) {
      throw new Error("startDateTime and endDateTime are required for timed events");
    }
    const start = new Date(startDateTime);
    const end = new Date(endDateTime);
    if (Number.isNaN(start.getTime()) || Number.isNaN(end.getTime())) {
      throw new Error("startDateTime/endDateTime must be valid ISO datetime values");
    }
    if (end < start) {
      throw new Error("endDateTime must be on or after startDateTime");
    }

    dtStartLine = `DTSTART:${formatICalDateTimeUtc(start)}`;
    dtEndLine = `DTEND:${formatICalDateTimeUtc(end)}`;
  }

  if (reminderMinutesBefore !== undefined && reminderDateTime !== undefined) {
    throw new Error("Use either reminderMinutesBefore or reminderDateTime, not both");
  }

  let alarmBlock = "";
  if (reminderMinutesBefore !== undefined || reminderDateTime !== undefined) {
    const action =
      typeof reminderAction === "string" && reminderAction.trim()
        ? reminderAction.trim().toUpperCase()
        : "DISPLAY";
    const alarmDescription = escapeICalText(reminderDescription || "Reminder");

    if (reminderMinutesBefore !== undefined) {
      const minutes = Number(reminderMinutesBefore);
      if (!Number.isFinite(minutes) || minutes < 0) {
        throw new Error("reminderMinutesBefore must be a number >= 0");
      }
      const roundedMinutes = Math.floor(minutes);
      alarmBlock = `\nBEGIN:VALARM
ACTION:${action}
TRIGGER:-PT${roundedMinutes}M
DESCRIPTION:${alarmDescription}
END:VALARM`;
    } else if (reminderDateTime !== undefined) {
      const reminderAt = new Date(reminderDateTime);
      if (Number.isNaN(reminderAt.getTime())) {
        throw new Error("reminderDateTime must be a valid ISO datetime value");
      }
      alarmBlock = `\nBEGIN:VALARM
ACTION:${action}
TRIGGER;VALUE=DATE-TIME:${formatICalDateTimeUtc(reminderAt)}
DESCRIPTION:${alarmDescription}
END:VALARM`;
    }
  }

  let vevent = `BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Nextcloud MCP Server//EN
BEGIN:VEVENT
UID:${uid}
SUMMARY:${escapeICalText(summary)}
${dtStartLine}
${dtEndLine}
CREATED:${formatICalDateTimeUtc(new Date())}`;

  if (description) {
    vevent += `\nDESCRIPTION:${escapeICalText(description)}`;
  }
  if (location) {
    vevent += `\nLOCATION:${escapeICalText(location)}`;
  }
  vevent += alarmBlock;

  vevent += `\nEND:VEVENT
END:VCALENDAR`;

  try {
    const caldavPath = `/remote.php/dav/calendars/${client.username}/personal/${uid}.ics`;

    await client.put(caldavPath, vevent, {
      "Content-Type": "text/calendar",
    });

    return {
      content: [
        {
          type: "text",
          text: `Calendar event created successfully with UID: ${uid}`,
        },
      ],
    };
  } catch (error: any) {
    throw new Error(`Failed to create calendar event: ${error.message}`);
  }
}

// --- Helpers ---

const debugEnabled = process.env.DEBUG_NEXTCLOUD_MCP === "1";

function debugLog(client: NextcloudClient, message: string): void {
  if (debugEnabled) {
    console.error(`[DEBUG_NEXTCLOUD_MCP] ${message}`);
  }
}

async function discoverCalendars(client: NextcloudClient): Promise<CalendarInfo[]> {
  const calendarsRoot = `/remote.php/dav/calendars/${client.username}/`;
  const requestBody = buildCalendarDiscoveryPropfindBody();

  debugLog(client, `PROPFIND calendars root: ${calendarsRoot}`);

  const response = await client.propfind(calendarsRoot, requestBody, "1");

  debugLog(
    client,
    `PROPFIND response status=200 body-preview=${response.slice(0, 500)}`
  );

  return parseCalendarsFromPROPFIND(response, calendarsRoot);
}