package dyzurbot

import (
	"context"
	"errors"
	"math/rand"
	"testing"
	"time"
)

type assignCall struct {
	week   DutyWeek
	p1, p2 string
}

// fireHarness builds a Reminder over a fixed rota/now with capturing send and
// assign funcs, so fire()'s branches can be asserted without Telegram or Google.
type fireHarness struct {
	sends    []string
	assigns  []assignCall
	assignFn AssignFunc
}

func newFireHarness(t *testing.T, rota Rota, now time.Time, seed int64) (*Reminder, *fireHarness) {
	t.Helper()
	h := &fireHarness{}
	send := func(_ context.Context, text string) error {
		h.sends = append(h.sends, text)
		return nil
	}
	assign := func(ctx context.Context, week DutyWeek, p1, p2 string) error {
		h.assigns = append(h.assigns, assignCall{week, p1, p2})
		if h.assignFn != nil {
			return h.assignFn(ctx, week, p1, p2)
		}
		return nil
	}
	r := &Reminder{
		store:  &Store{rota: rota},
		send:   send,
		assign: assign,
		cfg:    ReminderConfig{Loc: warsaw(t)},
		now:    func() time.Time { return now },
		rng:    rand.New(rand.NewSource(seed)),
	}
	return r, h
}

func TestFire(t *testing.T) {
	loc := warsaw(t)
	mon := time.Date(2026, 6, 15, 9, 0, 0, 0, loc) // Mon; this week starts 2026-06-15
	people := []Person{
		{Name: "Ala", DutyCount: 1},
		{Name: "Bartek", DutyCount: 2},
		{Name: "Cela", DutyCount: 3},
	}
	// filled is a fully-assigned week reused wherever a horizon must be left alone.
	filled := func(start string, row int) DutyWeek {
		return DutyWeek{WeekStart: day(t, start), Person1: "X", Person2: "Y", Row: row}
	}
	thisWeekFilled := DutyWeek{WeekStart: day(t, "2026-06-15"), Person1: "Jan", Person2: "Anna", Row: 5}
	wantThisReminder := "Przypomnienie: w tygodniu od 2026-06-15 dyżur mają Jan i Anna. Z góry dziękujemy!"

	t.Run("this week empty -> reminder only, never assigns", func(t *testing.T) {
		rota := Rota{
			Weeks: []DutyWeek{
				{WeekStart: day(t, "2026-06-15"), Row: 5}, // this: empty
				filled("2026-06-22", 6),                   // +1: filled
				filled("2026-06-29", 7),                   // +2: filled
			},
			People: people,
		}
		r, h := newFireHarness(t, rota, mon, 1)
		r.fire(context.Background())

		if len(h.assigns) != 0 {
			t.Errorf("assigns = %d, want 0 (this week is never auto-assigned)", len(h.assigns))
		}
		want := "Przypomnienie: w tygodniu od 2026-06-15 dyżur jest nieobsadzony."
		if len(h.sends) != 1 || h.sends[0] != want {
			t.Errorf("sends = %q, want [%q]", h.sends, want)
		}
	})

	t.Run("week ahead empty -> assign two lowest, back-fill row 6, announce", func(t *testing.T) {
		rota := Rota{
			Weeks: []DutyWeek{
				thisWeekFilled,
				{WeekStart: day(t, "2026-06-22"), Row: 6}, // +1: empty
				filled("2026-06-29", 7),                   // +2: filled
			},
			People: people,
		}
		r, h := newFireHarness(t, rota, mon, 1)
		r.fire(context.Background())

		if len(h.assigns) != 1 {
			t.Fatalf("assigns = %d, want 1", len(h.assigns))
		}
		a := h.assigns[0]
		if a.p1 != "Ala" || a.p2 != "Bartek" || a.week.Row != 6 {
			t.Errorf("assign = %+v, want Ala/Bartek on row 6", a)
		}
		wantAnnounce := "Nikt nie zgłosił się na dyżur w tygodniu od 2026-06-22, więc został przydzielony losowo: Ala i Bartek. Z góry dziękujemy za sprzątanie!"
		if len(h.sends) != 2 || h.sends[0] != wantThisReminder || h.sends[1] != wantAnnounce {
			t.Errorf("sends = %q,\n want [%q, %q]", h.sends, wantThisReminder, wantAnnounce)
		}
	})

	t.Run("two weeks ahead empty -> first warning", func(t *testing.T) {
		rota := Rota{
			Weeks: []DutyWeek{
				thisWeekFilled,
				filled("2026-06-22", 6),                   // +1: filled
				{WeekStart: day(t, "2026-06-29"), Row: 7}, // +2: empty
			},
			People: people,
		}
		r, h := newFireHarness(t, rota, mon, 1)
		r.fire(context.Background())

		if len(h.assigns) != 0 {
			t.Errorf("assigns = %d, want 0 (warning only, no assign at +2)", len(h.assigns))
		}
		wantWarning := "Dyżur w tygodniu od 2026-06-29 jest jeszcze nieobsadzony. Proszę się zgłaszać — w przeciwnym razie zostanie przydzielony losowo."
		if len(h.sends) != 2 || h.sends[0] != wantThisReminder || h.sends[1] != wantWarning {
			t.Errorf("sends = %q,\n want [%q, %q]", h.sends, wantThisReminder, wantWarning)
		}
	})

	t.Run("week ahead empty but fewer than 2 people -> no assign", func(t *testing.T) {
		rota := Rota{
			Weeks: []DutyWeek{
				thisWeekFilled,
				{WeekStart: day(t, "2026-06-22"), Row: 6},
				filled("2026-06-29", 7),
			},
			People: []Person{{Name: "Ala", DutyCount: 1}},
		}
		r, h := newFireHarness(t, rota, mon, 1)
		r.fire(context.Background())

		if len(h.assigns) != 0 {
			t.Errorf("assigns = %d, want 0", len(h.assigns))
		}
		if len(h.sends) != 1 || h.sends[0] != wantThisReminder {
			t.Errorf("sends = %q, want [%q]", h.sends, wantThisReminder)
		}
	})

	t.Run("week ahead empty but row unknown -> no assign", func(t *testing.T) {
		rota := Rota{
			Weeks: []DutyWeek{
				thisWeekFilled,
				{WeekStart: day(t, "2026-06-22"), Row: 0}, // unwritable row
				filled("2026-06-29", 7),
			},
			People: people,
		}
		r, h := newFireHarness(t, rota, mon, 1)
		r.fire(context.Background())

		if len(h.assigns) != 0 {
			t.Errorf("assigns = %d, want 0 (unwritable row)", len(h.assigns))
		}
		if len(h.sends) != 1 || h.sends[0] != wantThisReminder {
			t.Errorf("sends = %q, want [%q]", h.sends, wantThisReminder)
		}
	})

	t.Run("assign write fails -> attempted, no announcement", func(t *testing.T) {
		rota := Rota{
			Weeks: []DutyWeek{
				thisWeekFilled,
				{WeekStart: day(t, "2026-06-22"), Row: 6},
				filled("2026-06-29", 7),
			},
			People: people,
		}
		r, h := newFireHarness(t, rota, mon, 1)
		h.assignFn = func(context.Context, DutyWeek, string, string) error { return errors.New("boom") }
		r.fire(context.Background())

		if len(h.assigns) != 1 {
			t.Errorf("assigns = %d, want 1 (attempted)", len(h.assigns))
		}
		if len(h.sends) != 1 || h.sends[0] != wantThisReminder {
			t.Errorf("sends = %q, want [%q] (no announce on write failure)", h.sends, wantThisReminder)
		}
	})

	t.Run("partially-filled week ahead -> left alone", func(t *testing.T) {
		rota := Rota{
			Weeks: []DutyWeek{
				thisWeekFilled,
				{WeekStart: day(t, "2026-06-22"), Person1: "Ola", Row: 6}, // +1: one slot filled
				filled("2026-06-29", 7),
			},
			People: people,
		}
		r, h := newFireHarness(t, rota, mon, 1)
		r.fire(context.Background())

		if len(h.assigns) != 0 {
			t.Errorf("assigns = %d, want 0 (partial week is not empty)", len(h.assigns))
		}
		if len(h.sends) != 1 || h.sends[0] != wantThisReminder {
			t.Errorf("sends = %q, want [%q]", h.sends, wantThisReminder)
		}
	})
}

func TestChooseTwo(t *testing.T) {
	rng := rand.New(rand.NewSource(1))

	t.Run("picks two lowest counts, lowest first", func(t *testing.T) {
		people := []Person{
			{Name: "Ala", DutyCount: 3},
			{Name: "Bartek", DutyCount: 1},
			{Name: "Cela", DutyCount: 2},
		}
		p1, p2, ok := chooseTwo(people, rng)
		if !ok {
			t.Fatal("ok = false, want true")
		}
		if p1 != "Bartek" || p2 != "Cela" {
			t.Errorf("got (%q, %q), want (Bartek, Cela)", p1, p2)
		}
	})

	t.Run("ignores blank-name entries", func(t *testing.T) {
		people := []Person{
			{Name: "", DutyCount: 0},
			{Name: "Ala", DutyCount: 5},
			{Name: "Bartek", DutyCount: 6},
		}
		p1, p2, ok := chooseTwo(people, rng)
		if !ok || p1 != "Ala" || p2 != "Bartek" {
			t.Errorf("got (%q, %q, %v), want (Ala, Bartek, true)", p1, p2, ok)
		}
	})

	t.Run("fewer than two eligible -> ok=false", func(t *testing.T) {
		if _, _, ok := chooseTwo([]Person{{Name: "Ala"}}, rng); ok {
			t.Error("one person: ok = true, want false")
		}
		if _, _, ok := chooseTwo(nil, rng); ok {
			t.Error("no people: ok = true, want false")
		}
		if _, _, ok := chooseTwo([]Person{{Name: ""}, {Name: ""}}, rng); ok {
			t.Error("only blank names: ok = true, want false")
		}
	})

	t.Run("equal counts: random tie-break, distinct and deterministic per seed", func(t *testing.T) {
		people := []Person{
			{Name: "Ala", DutyCount: 1},
			{Name: "Bartek", DutyCount: 1},
			{Name: "Cela", DutyCount: 1},
		}
		p1, p2, ok := chooseTwo(people, rand.New(rand.NewSource(42)))
		if !ok {
			t.Fatal("ok = false, want true")
		}
		if p1 == p2 {
			t.Errorf("chose the same person twice: %q", p1)
		}
		names := map[string]bool{"Ala": true, "Bartek": true, "Cela": true}
		if !names[p1] || !names[p2] {
			t.Errorf("got (%q, %q), both must be from the roster", p1, p2)
		}
		// Same seed reproduces the same choice.
		q1, q2, _ := chooseTwo(people, rand.New(rand.NewSource(42)))
		if q1 != p1 || q2 != p2 {
			t.Errorf("not deterministic for a seed: (%q,%q) vs (%q,%q)", p1, p2, q1, q2)
		}
	})
}

func warsaw(t *testing.T) *time.Location {
	t.Helper()
	loc, err := time.LoadLocation("Europe/Warsaw")
	if err != nil {
		t.Skipf("Europe/Warsaw tzdata unavailable: %v", err)
	}
	return loc
}

func TestNextFire(t *testing.T) {
	loc := warsaw(t)
	at := func(y int, mo time.Month, d, h, mi int) time.Time {
		return time.Date(y, mo, d, h, mi, 0, 0, loc)
	}

	tests := []struct {
		name    string
		now     time.Time
		weekday time.Weekday
		hour    int
		want    time.Time
	}{
		{
			"same weekday before hour -> today",
			at(2026, 6, 15, 8, 0), time.Monday, 9, // Mon 08:00
			at(2026, 6, 15, 9, 0),
		},
		{
			"same weekday exactly at hour -> next week (strictly after)",
			at(2026, 6, 15, 9, 0), time.Monday, 9,
			at(2026, 6, 22, 9, 0),
		},
		{
			"same weekday after hour -> next week",
			at(2026, 6, 15, 10, 0), time.Monday, 9,
			at(2026, 6, 22, 9, 0),
		},
		{
			"later weekday -> upcoming target weekday",
			at(2026, 6, 17, 12, 0), time.Monday, 9, // Wed -> next Mon
			at(2026, 6, 22, 9, 0),
		},
		{
			"day before -> next day",
			at(2026, 6, 21, 23, 0), time.Monday, 9, // Sun 23:00 -> Mon 09:00
			at(2026, 6, 22, 9, 0),
		},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			got := nextFire(tc.now, tc.weekday, tc.hour, loc)
			if !got.Equal(tc.want) {
				t.Errorf("nextFire = %s, want %s", got.In(loc), tc.want.In(loc))
			}
			if !got.After(tc.now) {
				t.Errorf("nextFire %s not strictly after now %s", got.In(loc), tc.now.In(loc))
			}
		})
	}
}

// Across the spring-forward (2026-03-29 in Warsaw, clocks jump 02:00->03:00),
// the next Monday 09:00 must still be 09:00 wall-clock in Warsaw, proving the
// fire time is recomputed in the zone rather than by +7d UTC arithmetic.
func TestNextFireAcrossDST(t *testing.T) {
	loc := warsaw(t)
	now := time.Date(2026, 3, 28, 12, 0, 0, 0, loc) // Sat before DST
	got := nextFire(now, time.Monday, 9, loc).In(loc)

	if got.Weekday() != time.Monday || got.Hour() != 9 || got.Minute() != 0 {
		t.Fatalf("got %s, want Monday 09:00 Warsaw", got)
	}
	if y, m, d := got.Date(); y != 2026 || m != time.March || d != 30 {
		t.Errorf("got date %04d-%02d-%02d, want 2026-03-30", y, m, d)
	}
}

func TestReminderText(t *testing.T) {
	// Week of 2026-06-29; target lands inside it.
	target := day(t, "2026-06-30")
	rota := func(p1, p2 string) Rota {
		return Rota{Weeks: []DutyWeek{week(t, "2026-06-29", p1, p2)}}
	}

	tests := []struct {
		name   string
		rota   Rota
		target time.Time
		wantOK bool
		want   string
	}{
		{
			"both people",
			rota("Ala", "Bartek"), target, true,
			"Przypomnienie: w tygodniu od 2026-06-29 dyżur mają Ala i Bartek. Z góry dziękujemy!",
		},
		{
			"one person",
			rota("Ala", ""), target, true,
			"Przypomnienie: w tygodniu od 2026-06-29 dyżur ma Ala. Z góry dziękujemy!",
		},
		{
			"nobody assigned",
			rota("", ""), target, true,
			"Przypomnienie: w tygodniu od 2026-06-29 dyżur jest nieobsadzony.",
		},
		{
			"no matching week -> skip",
			rota("Ala", "Bartek"), day(t, "2026-09-01"), false,
			"",
		},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			got, ok := reminderText(tc.rota, tc.target)
			if ok != tc.wantOK {
				t.Fatalf("ok = %v, want %v", ok, tc.wantOK)
			}
			if ok && got != tc.want {
				t.Errorf("reminderText = %q, want %q", got, tc.want)
			}
		})
	}
}

func TestReminderTextMentions(t *testing.T) {
	target := day(t, "2026-06-30")
	people := []Person{
		{Name: "Ala", Handle: "@ala"},    // stored with leading @
		{Name: "Bartek", Handle: "bart"}, // stored without @ -> normalized
		{Name: "Cela", Handle: ""},       // present but no handle -> plain name
	}
	rota := func(p1, p2 string) Rota {
		return Rota{Weeks: []DutyWeek{week(t, "2026-06-29", p1, p2)}, People: people}
	}

	tests := []struct {
		name string
		rota Rota
		want string
	}{
		{
			"both have handles",
			rota("Ala", "Bartek"),
			"Przypomnienie: w tygodniu od 2026-06-29 dyżur mają @ala i @bart. Z góry dziękujemy!",
		},
		{
			"one handle, one missing -> mixed",
			rota("Ala", "Cela"),
			"Przypomnienie: w tygodniu od 2026-06-29 dyżur mają @ala i Cela. Z góry dziękujemy!",
		},
		{
			"name not in people list -> plain name",
			rota("Ala", "Zenon"),
			"Przypomnienie: w tygodniu od 2026-06-29 dyżur mają @ala i Zenon. Z góry dziękujemy!",
		},
		{
			"single person with handle",
			rota("Bartek", ""),
			"Przypomnienie: w tygodniu od 2026-06-29 dyżur ma @bart. Z góry dziękujemy!",
		},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			got, ok := reminderText(tc.rota, target)
			if !ok {
				t.Fatalf("ok = false, want true")
			}
			if got != tc.want {
				t.Errorf("reminderText = %q, want %q", got, tc.want)
			}
		})
	}
}

func TestParseWeekday(t *testing.T) {
	tests := []struct {
		in      string
		want    time.Weekday
		wantErr bool
	}{
		{"Monday", time.Monday, false},
		{"Sunday", time.Sunday, false},
		{"monday", time.Monday, false}, // case-insensitive
		{"Funday", 0, true},
		{"", 0, true},
	}
	for _, tc := range tests {
		t.Run(tc.in, func(t *testing.T) {
			got, err := parseWeekday(tc.in)
			if (err != nil) != tc.wantErr {
				t.Fatalf("err = %v, wantErr %v", err, tc.wantErr)
			}
			if err == nil && got != tc.want {
				t.Errorf("parseWeekday(%q) = %v, want %v", tc.in, got, tc.want)
			}
		})
	}
}