package web

import (
	"net/http/httptest"
	"strings"
	"testing"
	"time"

	"github.com/m/projax/store"
)

// TestCalendarLayoutMondayLead seeds a synthetic month whose first day is a
// Friday (May 2026) and confirms the layout function:
//   - First cell of week 0 is Monday April 27 2026 (adjacent-month).
//   - Last cell of the final week is Sunday May 31 2026 — the May 31st
//     itself falls on a Sunday, so no trailing pad days are needed.
//   - Total weeks = 5 (4 spillover Mondays + 31 days = 35 cells / 7).
func TestCalendarLayoutMondayLead(t *testing.T) {
	loc := time.Local
	may := time.Date(2026, 5, 1, 0, 0, 0, 0, loc)
	gridStart := may.AddDate(0, 0, -mondayWeekday(may)) // Apr 27 2026
	gridEnd := time.Date(2026, 6, 1, 0, 0, 0, 0, loc)   // Jun 1 2026 (exclusive — May 31 is the final cell)

	weeks := layoutCalendarWeeks(may, gridStart, gridEnd, may, nil)
	if len(weeks) != 5 {
		t.Fatalf("expected 5 weeks for May 2026 (Fri-leading, Sun-trailing), got %d", len(weeks))
	}
	first := weeks[0].Days[0]
	if first.DateKey != "2026-04-27" {
		t.Errorf("first cell DateKey = %q, want 2026-04-27", first.DateKey)
	}
	if !first.IsAdjacent {
		t.Errorf("first cell should be IsAdjacent (Apr 27 lives in April)")
	}
	last := weeks[4].Days[6]
	if last.DateKey != "2026-05-31" {
		t.Errorf("last cell DateKey = %q, want 2026-05-31", last.DateKey)
	}
	if last.IsAdjacent {
		t.Errorf("last cell should NOT be adjacent — May 31 is within May")
	}
}

// TestCalendarLayoutTrailingPad picks a month whose last day is a Monday
// (June 2026) — the rectangular grid requires six trailing pad days to
// close the week, yielding six rows total.
func TestCalendarLayoutTrailingPad(t *testing.T) {
	loc := time.Local
	june := time.Date(2026, 6, 1, 0, 0, 0, 0, loc) // Monday
	gridStart := june                              // monthStart already a Monday → no lead
	// June has 30 days, ends on Tuesday. Pad to Sunday = +5 days → grid runs through Jul 5.
	gridEnd := time.Date(2026, 7, 6, 0, 0, 0, 0, loc)

	weeks := layoutCalendarWeeks(june, gridStart, gridEnd, june, nil)
	if len(weeks) != 5 {
		t.Fatalf("expected 5 weeks for June 2026 (Mon-leading), got %d", len(weeks))
	}
	if weeks[0].Days[0].DateKey != "2026-06-01" {
		t.Errorf("first cell = %q, want 2026-06-01", weeks[0].Days[0].DateKey)
	}
	if weeks[4].Days[6].DateKey != "2026-07-05" {
		t.Errorf("last trailing cell = %q, want 2026-07-05", weeks[4].Days[6].DateKey)
	}
	if !weeks[4].Days[6].IsAdjacent {
		t.Errorf("July 5 cell should be IsAdjacent (lives in next month)")
	}
}

// TestCalendarTodayCell proves the IsToday flag fires on the right cell.
func TestCalendarTodayCell(t *testing.T) {
	loc := time.Local
	may := time.Date(2026, 5, 1, 0, 0, 0, 0, loc)
	today := time.Date(2026, 5, 14, 0, 0, 0, 0, loc)
	gridStart := may.AddDate(0, 0, -mondayWeekday(may))
	gridEnd := time.Date(2026, 6, 1, 0, 0, 0, 0, loc)
	weeks := layoutCalendarWeeks(may, gridStart, gridEnd, today, nil)
	found := false
	for _, wk := range weeks {
		for _, d := range wk.Days {
			if d.DateKey == "2026-05-14" {
				found = true
				if !d.IsToday {
					t.Errorf("cell for today (2026-05-14) should be IsToday")
				}
			} else if d.IsToday {
				t.Errorf("cell %s should NOT be IsToday", d.DateKey)
			}
		}
	}
	if !found {
		t.Fatalf("did not find cell for today in the grid")
	}
}

// TestCalendarCellRowOverflow proves that a day with more than three rows
// renders three visible rows and surfaces the remainder via ExtraCount so
// the template can emit a "+N more" link.
func TestCalendarCellRowOverflow(t *testing.T) {
	loc := time.Local
	may := time.Date(2026, 5, 1, 0, 0, 0, 0, loc)
	gridStart := may.AddDate(0, 0, -mondayWeekday(may))
	gridEnd := time.Date(2026, 6, 1, 0, 0, 0, 0, loc)
	dummy := &store.Item{ID: "id", Title: "t", Slug: "t"}
	rows := []calendarRow{
		{Kind: "event", Item: dummy, ItemPath: "t", Summary: "a"},
		{Kind: "event", Item: dummy, ItemPath: "t", Summary: "b"},
		{Kind: "event", Item: dummy, ItemPath: "t", Summary: "c"},
		{Kind: "event", Item: dummy, ItemPath: "t", Summary: "d"},
		{Kind: "event", Item: dummy, ItemPath: "t", Summary: "e"},
	}
	byDay := map[string][]calendarRow{"2026-05-15": rows}
	weeks := layoutCalendarWeeks(may, gridStart, gridEnd, may, byDay)
	var cell *calendarDay
	for _, wk := range weeks {
		for i, d := range wk.Days {
			if d.DateKey == "2026-05-15" {
				cell = &wk.Days[i]
			}
		}
	}
	if cell == nil {
		t.Fatalf("did not find May 15 cell")
	}
	if len(cell.Rows) != calendarMaxRowsPerCell {
		t.Errorf("len(Rows) = %d, want %d (cap)", len(cell.Rows), calendarMaxRowsPerCell)
	}
	if cell.ExtraCount != 2 {
		t.Errorf("ExtraCount = %d, want 2 (5 seeded - 3 visible)", cell.ExtraCount)
	}
	if cell.TotalRows != 5 {
		t.Errorf("TotalRows = %d, want 5", cell.TotalRows)
	}
}

// TestMondayWeekday pins the Monday=0 weekday conversion that drives the
// lead-day count. The Sunday=0 default in Go's time package would put
// Sunday at index 0 of the grid — wrong for the German week convention.
func TestMondayWeekday(t *testing.T) {
	cases := []struct {
		day  time.Weekday
		want int
	}{
		{time.Monday, 0}, {time.Tuesday, 1}, {time.Wednesday, 2},
		{time.Thursday, 3}, {time.Friday, 4}, {time.Saturday, 5}, {time.Sunday, 6},
	}
	for _, c := range cases {
		// Pick a reference Monday and offset to get the weekday under test.
		ref := time.Date(2026, 5, 4, 0, 0, 0, 0, time.UTC) // Mon
		probe := ref.AddDate(0, 0, int(c.day-time.Monday+7)%7)
		if probe.Weekday() != c.day {
			t.Fatalf("setup bug: probe weekday = %v, want %v", probe.Weekday(), c.day)
		}
		if got := mondayWeekday(probe); got != c.want {
			t.Errorf("mondayWeekday(%v) = %d, want %d", c.day, got, c.want)
		}
	}
}

// TestFormatCalendarLongLabel exercises the per-cell long German label
// used by the mobile breakpoint (hidden on desktop via CSS). The label
// matters because on a 360px-wide phone the bare day number no longer
// carries weekday context — the CSS collapses the column header.
func TestFormatCalendarLongLabel(t *testing.T) {
	cases := map[string]string{
		"2026-05-04": "Mo., 4. Mai",      // Monday
		"2026-05-14": "Do., 14. Mai",     // Thursday
		"2026-03-15": "So., 15. März",    // Sunday in March (uses März)
		"2026-12-31": "Do., 31. Dez",
	}
	for in, want := range cases {
		t.Run(in, func(t *testing.T) {
			d, _ := time.Parse("2006-01-02", in)
			if got := formatCalendarLongLabel(d); got != want {
				t.Errorf("formatCalendarLongLabel(%s) = %q, want %q", in, got, want)
			}
		})
	}
}

// TestFormatMonthLabel confirms the German month names render — m reads
// /calendar primarily in the German register and the label is the most
// visible piece of chrome.
func TestFormatMonthLabel(t *testing.T) {
	cases := map[string]string{
		"2026-01-01": "Januar 2026",
		"2026-03-15": "März 2026",
		"2026-05-01": "Mai 2026",
		"2026-12-31": "Dezember 2026",
	}
	for in, want := range cases {
		t.Run(in, func(t *testing.T) {
			d, _ := time.Parse("2006-01-02", in)
			if got := formatMonthLabel(d); got != want {
				t.Errorf("formatMonthLabel(%s) = %q, want %q", in, got, want)
			}
		})
	}
}

// TestParseCalendarQueryDefaults proves month + kinds default to current
// month + all-three.
func TestParseCalendarQueryDefaults(t *testing.T) {
	now := time.Date(2026, 5, 14, 10, 0, 0, 0, time.UTC)
	r := httptest.NewRequest("GET", "/views/calendar", nil)
	q := parseCalendarQuery(r, now)
	if q.Month.Format("2006-01") != "2026-05" {
		t.Errorf("default month = %s, want 2026-05", q.Month.Format("2006-01"))
	}
	kinds := q.activeKinds()
	if len(kinds) != 3 {
		t.Errorf("default activeKinds len = %d, want 3 (event/todo/doc)", len(kinds))
	}
	wantKinds := strings.Join(kinds, ",")
	for _, k := range []string{"event", "todo", "doc"} {
		if !strings.Contains(wantKinds, k) {
			t.Errorf("activeKinds missing %s: %v", k, kinds)
		}
	}
}

// TestParseCalendarQueryMonthParam proves a `?month=YYYY-MM` URL param
// overrides the default. Bookmarkability matters because the prev/next
// nav writes to this exact key.
func TestParseCalendarQueryMonthParam(t *testing.T) {
	now := time.Date(2026, 5, 14, 10, 0, 0, 0, time.UTC)
	r := httptest.NewRequest("GET", "/views/calendar?month=2026-08", nil)
	q := parseCalendarQuery(r, now)
	if q.Month.Format("2006-01") != "2026-08" {
		t.Errorf("parsed month = %s, want 2026-08", q.Month.Format("2006-01"))
	}
}

// TestParseCalendarQueryKindFilter proves `?kind=event,doc` narrows the
// kind set and drops unknown values.
func TestParseCalendarQueryKindFilter(t *testing.T) {
	now := time.Date(2026, 5, 14, 10, 0, 0, 0, time.UTC)
	r := httptest.NewRequest("GET", "/views/calendar?kind=event,doc,junk,creation", nil)
	q := parseCalendarQuery(r, now)
	got := strings.Join(q.activeKinds(), ",")
	want := "doc,event" // sorted alphabetically; creation is excluded by design, junk dropped
	if got != want {
		t.Errorf("activeKinds = %q, want %q", got, want)
	}
}