import { describe, expect, it } from "vitest";
import {
  canonicalRepair,
  findConflicts,
  localTimeCandidates,
  mergeCalendars,
  parseCalendar,
  previewOccurrences,
  timezoneDiagnostics,
} from "../../src/calendar/model";

const recurring = `BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//test//EN\r\nBEGIN:VEVENT\r\nUID:a\r\nDTSTAMP:20260101T000000Z\r\nDTSTART:20260901T100000Z\r\nDTEND:20260901T110000Z\r\nRRULE:FREQ=DAILY;COUNT=3\r\nSUMMARY:A\r\nEND:VEVENT\r\nBEGIN:VEVENT\r\nUID:b\r\nDTSTART:20260901T103000Z\r\nDTEND:20260901T120000Z\r\nSUMMARY:B\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n`;

describe("calendar model", () => {
  it("parses and expands recurrence under a bound", () => {
    const document = parseCalendar(recurring);
    expect(document.events).toHaveLength(2);
    const preview = previewOccurrences(document, 10, 30);
    expect(preview.occurrences.filter((item) => item.uid === "a")).toHaveLength(
      3,
    );
    expect(findConflicts(preview.occurrences)).toEqual(
      expect.arrayContaining([expect.objectContaining({ kind: "overlap" })]),
    );
  });

  it("canonicalizes line endings and supplies required metadata", () => {
    const input = `BEGIN:VCALENDAR\nBEGIN:VEVENT\nUID:x\nDTSTART:20260901T100000Z\nDTEND:20260901T110000Z\nEND:VEVENT\nEND:VCALENDAR\n`;
    const repaired = canonicalRepair(input);
    expect(repaired.source).toContain("VERSION:2.0\r\n");
    expect(repaired.source).toContain("PRODID:");
    expect(repaired.source).not.toMatch(/(?<!\r)\n/u);
  });

  it("merges event identity using sequence then stamp", () => {
    const newer = recurring.replace(
      "SUMMARY:A",
      "SEQUENCE:2\r\nSUMMARY:Updated A",
    );
    const merged = mergeCalendars([
      parseCalendar(recurring),
      parseCalendar(newer),
    ]);
    expect(merged.deduplicated).toBe(2);
    expect(merged.source).toContain("SUMMARY:Updated A");
    expect(parseCalendar(merged.source).events).toHaveLength(2);
  });

  it("never deduplicates separate UID-less events", () => {
    const uidless = `BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//test//EN\r\nBEGIN:VEVENT\r\nDTSTART:20260901T100000Z\r\nDTEND:20260901T110000Z\r\nSUMMARY:No identity\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n`;
    const merged = mergeCalendars([
      parseCalendar(uidless),
      parseCalendar(uidless),
    ]);
    expect(merged.deduplicated).toBe(0);
    expect(parseCalendar(merged.source).events).toHaveLength(2);
    expect(merged.diagnostics.map((item) => item.message).join(" ")).toMatch(
      /UID-less/u,
    );
  });

  it("uses embedded VTIMEZONE observances for custom TZIDs", () => {
    const custom = `BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//test//EN\r\nBEGIN:VTIMEZONE\r\nTZID:Custom/Test\r\nBEGIN:STANDARD\r\nDTSTART:19700101T000000\r\nTZOFFSETFROM:+0230\r\nTZOFFSETTO:+0230\r\nTZNAME:CST\r\nEND:STANDARD\r\nEND:VTIMEZONE\r\nBEGIN:VEVENT\r\nUID:custom\r\nDTSTART;TZID=Custom/Test:20260901T100000\r\nDTEND;TZID=Custom/Test:20260901T110000\r\nSUMMARY:Custom zone\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n`;
    const document = parseCalendar(custom);
    expect(document.timezones[0]?.tzid).toBe("Custom/Test");
    expect(document.events[0]?.startMs).toBe(
      Date.parse("2026-09-01T07:30:00.000Z"),
    );
  });

  it("classifies DST overlaps and reports yearly transitions", () => {
    const candidates = localTimeCandidates("2026-10-25T02:30", "Europe/Berlin");
    expect(candidates).toHaveLength(2);
    expect(timezoneDiagnostics("Europe/Berlin", 2026).transitions).toHaveLength(
      2,
    );
  });

  it("rejects unbounded and malformed inputs", () => {
    expect(() => previewOccurrences(parseCalendar(recurring), 501, 30)).toThrow(
      /1–500/u,
    );
    expect(() => parseCalendar("not a calendar")).toThrow(
      /parse failed|root component/u,
    );
  });
});