import { describe, expect, test } from "vitest";
import {
  findSlots,
  inWorkingHours,
  therapistAvailable,
  type FindSlotsOptions,
  type RoomState,
  type ServiceLite,
  type TherapistState,
  type WorkingHoursEntry,
} from "@/lib/availability";

// ============================================================
// Fixture helpers
// ============================================================

const TZ = "America/New_York";
const D = (iso: string) => new Date(iso);

// Tue 2026-05-05 in the New York practice timezone:
//   10:00 EDT == 14:00 UTC (EDT = UTC-4)
// We'll use this date a lot in fixtures.
const TUE_LOCAL_10AM = D("2026-05-05T14:00:00Z"); // 2026-05-05 10:00 EDT
const TUE_LOCAL_11AM = D("2026-05-05T15:00:00Z");
const TUE_LOCAL_12PM = D("2026-05-05T16:00:00Z");
const TUE_LOCAL_5PM = D("2026-05-05T21:00:00Z");
const TUE_LOCAL_7PM = D("2026-05-05T23:00:00Z");
const TUE_LOCAL_9AM = D("2026-05-05T13:00:00Z"); // before opening

// Spring-forward 2026 in US Eastern: Mar 8 2026, local 02:00 EST → 03:00 EDT.
const SPRING_FORWARD_SUN_LOCAL_10AM = D("2026-03-08T14:00:00Z"); // 10:00 EDT after the jump

const SERVICE_60MIN: ServiceLite = {
  id: "svc-60",
  durationMin: 60,
  bufferAfterMin: 15,
  requiredTherapistTags: [],
  requiredRoomTags: [],
};

const SERVICE_90MIN_PRENATAL: ServiceLite = {
  id: "svc-90-prenatal",
  durationMin: 90,
  bufferAfterMin: 20,
  requiredTherapistTags: ["prenatal-cert"],
  requiredRoomTags: ["prenatal-table"],
};

const FULL_WEEK_10_TO_19: WorkingHoursEntry[] = [0, 1, 2, 3, 4, 5, 6].map((d) => ({
  weekday: d,
  startMin: 10 * 60,
  endMin: 19 * 60,
}));

const TUE_THRU_SAT_10_TO_19: WorkingHoursEntry[] = [2, 3, 4, 5, 6].map((d) => ({
  weekday: d,
  startMin: 10 * 60,
  endMin: 19 * 60,
}));

function baseTherapist(overrides: Partial<TherapistState> = {}): TherapistState {
  return {
    id: "t1",
    active: true,
    tags: new Set(["swedish"]),
    serviceIds: new Set([SERVICE_60MIN.id]),
    workingHours: TUE_THRU_SAT_10_TO_19,
    overrides: [],
    bookings: [],
    ...overrides,
  };
}

function baseRoom(overrides: Partial<RoomState> = {}): RoomState {
  return {
    id: "r1",
    active: true,
    tags: new Set<string>(),
    blocks: [],
    bookings: [],
    ...overrides,
  };
}

function baseOpts(overrides: Partial<FindSlotsOptions> = {}): FindSlotsOptions {
  return {
    service: SERVICE_60MIN,
    from: TUE_LOCAL_10AM,
    to: TUE_LOCAL_12PM,
    therapists: [baseTherapist()],
    rooms: [baseRoom()],
    practiceTz: TZ,
    slotGranularityMin: 15,
    ...overrides,
  };
}

// ============================================================
// inWorkingHours — direct tests
// ============================================================

describe("inWorkingHours", () => {
  test("slot inside Tuesday working hours is accepted", () => {
    expect(
      inWorkingHours(TUE_THRU_SAT_10_TO_19, TUE_LOCAL_10AM, TUE_LOCAL_11AM, TZ),
    ).toBe(true);
  });

  test("slot before opening is rejected", () => {
    expect(
      inWorkingHours(TUE_THRU_SAT_10_TO_19, TUE_LOCAL_9AM, TUE_LOCAL_10AM, TZ),
    ).toBe(false);
  });

  test("slot ending exactly at closing is accepted (endMin is inclusive of equality)", () => {
    expect(
      inWorkingHours(TUE_THRU_SAT_10_TO_19, TUE_LOCAL_5PM, TUE_LOCAL_7PM, TZ),
    ).toBe(true);
  });

  test("Monday slot rejected when Mon is not a working day", () => {
    // 2026-05-04 is a Monday
    const monLocal10am = D("2026-05-04T14:00:00Z");
    const monLocal11am = D("2026-05-04T15:00:00Z");
    expect(
      inWorkingHours(TUE_THRU_SAT_10_TO_19, monLocal10am, monLocal11am, TZ),
    ).toBe(false);
  });

  test("DST spring-forward Sunday: 10:00 local works because we shift to EDT", () => {
    // Even though the local clock skipped 02:00–03:00 EST, 10:00 EDT is well after.
    expect(
      inWorkingHours(
        FULL_WEEK_10_TO_19,
        SPRING_FORWARD_SUN_LOCAL_10AM,
        D("2026-03-08T15:00:00Z"), // 11:00 EDT
        TZ,
      ),
    ).toBe(true);
  });

  test("effectiveFrom/effectiveTo bracket is enforced", () => {
    const wh: WorkingHoursEntry[] = [{
      weekday: 2,
      startMin: 10 * 60,
      endMin: 19 * 60,
      effectiveFrom: D("2026-06-01T00:00:00Z"),
    }];
    // Slot before effectiveFrom should not match.
    expect(
      inWorkingHours(wh, TUE_LOCAL_10AM, TUE_LOCAL_11AM, TZ),
    ).toBe(false);
  });

  test("cross-midnight slot is rejected", () => {
    // Hypothetical 11pm-1am slot would span two local days.
    expect(
      inWorkingHours(
        FULL_WEEK_10_TO_19,
        D("2026-05-06T03:00:00Z"), // 23:00 local Tuesday
        D("2026-05-06T05:00:00Z"), // 01:00 local Wednesday
        TZ,
      ),
    ).toBe(false);
  });
});

// ============================================================
// therapistAvailable — direct tests
// ============================================================

describe("therapistAvailable", () => {
  test("free therapist in working hours is available", () => {
    const t = baseTherapist();
    expect(therapistAvailable(t, TUE_LOCAL_10AM, TUE_LOCAL_11AM, TZ)).toBe(true);
  });

  test("booking overlap blocks the slot", () => {
    const t = baseTherapist({
      bookings: [{ startsAt: TUE_LOCAL_10AM, endsAt: TUE_LOCAL_11AM }],
    });
    expect(
      therapistAvailable(
        t,
        D("2026-05-05T14:30:00Z"), // 10:30 EDT — overlaps 10:00–11:00
        D("2026-05-05T15:30:00Z"),
        TZ,
      ),
    ).toBe(false);
  });

  test("BLOCK override during working hours blocks the slot", () => {
    const t = baseTherapist({
      overrides: [{
        kind: "BLOCK",
        startsAt: D("2026-05-05T14:30:00Z"),
        endsAt: D("2026-05-05T15:30:00Z"),
      }],
    });
    expect(therapistAvailable(t, TUE_LOCAL_10AM, TUE_LOCAL_11AM, TZ)).toBe(false);
  });

  test("EXTRA_HOURS opens a slot outside regular working hours", () => {
    // Therapist's regular hours don't include Sunday; EXTRA_HOURS does.
    const t = baseTherapist({
      workingHours: TUE_THRU_SAT_10_TO_19, // no Sunday
      overrides: [{
        kind: "EXTRA_HOURS",
        startsAt: D("2026-05-10T14:00:00Z"), // Sun 10:00 EDT
        endsAt: D("2026-05-10T18:00:00Z"),   // Sun 14:00 EDT
      }],
    });
    expect(
      therapistAvailable(
        t,
        D("2026-05-10T14:00:00Z"),
        D("2026-05-10T15:00:00Z"),
        TZ,
      ),
    ).toBe(true);
  });
});

// ============================================================
// findSlots — integration
// ============================================================

describe("findSlots", () => {
  test("baseline: 60-min service in a 2-hour window emits 5 slots at 15-min granularity", () => {
    // Window 10:00–12:00 local. Service is 60 min. Slots can start at
    // 10:00, 10:15, 10:30, 10:45, 11:00 (last finishes at 12:00).
    const slots = findSlots(baseOpts());
    expect(slots).toHaveLength(5);
    expect(slots[0].startsAt).toEqual(TUE_LOCAL_10AM);
    expect(slots[4].startsAt).toEqual(TUE_LOCAL_11AM);
    expect(slots[4].endsAt).toEqual(TUE_LOCAL_12PM);
  });

  test("empty therapists list yields no slots", () => {
    expect(findSlots(baseOpts({ therapists: [] }))).toEqual([]);
  });

  test("empty rooms list yields no slots", () => {
    expect(findSlots(baseOpts({ rooms: [] }))).toEqual([]);
  });

  test("therapist tag mismatch excludes therapist", () => {
    // Service requires prenatal-cert, but the only room has the right tag.
    const slots = findSlots(
      baseOpts({
        service: SERVICE_90MIN_PRENATAL,
        // Window large enough for one 90-min slot
        to: D("2026-05-05T15:30:00Z"),
        therapists: [
          baseTherapist({
            tags: new Set(["swedish"]), // missing prenatal-cert
            serviceIds: new Set([SERVICE_90MIN_PRENATAL.id]),
          }),
        ],
        rooms: [
          baseRoom({ tags: new Set(["prenatal-table"]) }),
        ],
      }),
    );
    expect(slots).toEqual([]);
  });

  test("room tag mismatch excludes room", () => {
    const slots = findSlots(
      baseOpts({
        service: SERVICE_90MIN_PRENATAL,
        to: D("2026-05-05T15:30:00Z"),
        therapists: [
          baseTherapist({
            tags: new Set(["prenatal-cert"]),
            serviceIds: new Set([SERVICE_90MIN_PRENATAL.id]),
          }),
        ],
        rooms: [
          baseRoom({ tags: new Set<string>() }), // missing prenatal-table
        ],
      }),
    );
    expect(slots).toEqual([]);
  });

  test("ServiceTherapist allowlist excludes therapists not opted in", () => {
    const slots = findSlots(
      baseOpts({
        therapists: [
          baseTherapist({ serviceIds: new Set(["some-other-service"]) }),
        ],
      }),
    );
    expect(slots).toEqual([]);
  });

  test("inactive therapist excluded", () => {
    expect(
      findSlots(baseOpts({ therapists: [baseTherapist({ active: false })] })),
    ).toEqual([]);
  });

  test("inactive room excluded", () => {
    expect(
      findSlots(baseOpts({ rooms: [baseRoom({ active: false })] })),
    ).toEqual([]);
  });

  test("therapist on PTO via BLOCK override has no slots in PTO window", () => {
    const slots = findSlots(
      baseOpts({
        therapists: [
          baseTherapist({
            overrides: [{
              kind: "BLOCK",
              startsAt: TUE_LOCAL_10AM,
              endsAt: TUE_LOCAL_12PM,
            }],
          }),
        ],
      }),
    );
    expect(slots).toEqual([]);
  });

  test("room buffer prevents back-to-back booking inside the buffer window", () => {
    // Existing booking 10:00–11:00 with 15-min buffer ⇒ room locked till 11:15.
    // Window 10:00–12:00 ⇒ next legal start is 11:15. With granularity 15 and
    // duration 60, candidates 11:15 (end 12:15 – out of window!), so 0 slots
    // beyond the existing one. But the existing booking's slot itself isn't a
    // candidate (the room is occupied). Expand window to 12:30 to test legal
    // resumption at 11:15.
    const slots = findSlots(
      baseOpts({
        to: D("2026-05-05T16:30:00Z"), // 12:30 EDT
        rooms: [
          baseRoom({
            bookings: [{
              startsAt: TUE_LOCAL_10AM,
              endsAt: D("2026-05-05T15:15:00Z"), // = 11:00 + 15 min buffer
            }],
          }),
        ],
      }),
    );
    // Legal slots: 11:15 → 12:15 (only one, since 11:30 → 12:30 also fits).
    const starts = slots.map((s) => s.startsAt.toISOString());
    expect(starts).toContain("2026-05-05T15:15:00.000Z"); // 11:15 EDT
    expect(starts).toContain("2026-05-05T15:30:00.000Z"); // 11:30 EDT
    // Should NOT include any time before 11:15 (room locked).
    expect(
      starts.filter((s) => s < "2026-05-05T15:15:00.000Z"),
    ).toEqual([]);
  });

  test("room block excludes that room during the block window", () => {
    const slots = findSlots(
      baseOpts({
        rooms: [
          baseRoom({
            blocks: [{
              startsAt: D("2026-05-05T14:30:00Z"), // 10:30 EDT
              endsAt: D("2026-05-05T15:30:00Z"),   // 11:30 EDT
            }],
          }),
        ],
      }),
    );
    // 10:00–11:00 slot? Block starts 10:30, so room buffer on slot 10:00 → 11:15
    // overlaps the block — excluded.
    const starts = slots.map((s) => s.startsAt.toISOString());
    expect(starts).not.toContain("2026-05-05T14:00:00.000Z"); // 10:00
    expect(starts).not.toContain("2026-05-05T14:15:00.000Z"); // 10:15
  });

  test("preferredTherapistId restricts results to that therapist", () => {
    const t1 = baseTherapist({ id: "t1" });
    const t2 = baseTherapist({ id: "t2" });
    const slots = findSlots(
      baseOpts({
        therapists: [t1, t2],
        preferredTherapistId: "t2",
      }),
    );
    for (const s of slots) {
      expect(s.candidateTherapistIds).toEqual(["t2"]);
    }
    expect(slots.length).toBeGreaterThan(0);
  });

  test("from-time not on grid is rounded up to the next granular boundary", () => {
    const slots = findSlots(
      baseOpts({
        from: D("2026-05-05T14:07:00Z"), // 10:07 EDT — should round up to 10:15
        to: D("2026-05-05T16:00:00Z"),   // 12:00 EDT
      }),
    );
    expect(slots[0].startsAt).toEqual(D("2026-05-05T14:15:00Z"));
  });

  test("out-of-working-hours window yields no slots", () => {
    const slots = findSlots(
      baseOpts({
        from: D("2026-05-05T11:00:00Z"), // 7:00 EDT
        to: D("2026-05-05T13:00:00Z"),   // 9:00 EDT — entirely before open
      }),
    );
    expect(slots).toEqual([]);
  });

  test("DST spring-forward Sunday: slot grid still produces clean slots after the jump", () => {
    const slots = findSlots(
      baseOpts({
        from: D("2026-03-08T14:00:00Z"), // 10:00 EDT (after the jump)
        to: D("2026-03-08T16:00:00Z"),   // 12:00 EDT
        therapists: [
          baseTherapist({ workingHours: FULL_WEEK_10_TO_19 }),
        ],
      }),
    );
    expect(slots.length).toBeGreaterThan(0);
    // First slot should be exactly 10:00 EDT.
    expect(slots[0].startsAt).toEqual(SPRING_FORWARD_SUN_LOCAL_10AM);
  });

  test("returns slots sorted by start time, ascending", () => {
    const slots = findSlots(
      baseOpts({
        to: D("2026-05-05T17:00:00Z"), // 13:00 EDT — wider window
      }),
    );
    for (let i = 1; i < slots.length; i++) {
      expect(slots[i].startsAt.getTime()).toBeGreaterThan(
        slots[i - 1].startsAt.getTime(),
      );
    }
  });

  test("two therapists, only one available at a given slot — slot still emitted with that one as candidate", () => {
    const t1 = baseTherapist({
      id: "t1",
      bookings: [{
        startsAt: TUE_LOCAL_10AM,
        endsAt: TUE_LOCAL_11AM,
      }],
    });
    const t2 = baseTherapist({ id: "t2" });
    const slots = findSlots(baseOpts({ therapists: [t1, t2] }));
    const tenAm = slots.find(
      (s) => s.startsAt.toISOString() === "2026-05-05T14:00:00.000Z",
    );
    expect(tenAm).toBeDefined();
    expect(tenAm!.candidateTherapistIds).toEqual(["t2"]);
  });
});