package czech

import (
	"reflect"
	"testing"
)

func TestParseMonthReferences(t *testing.T) {
	t.Parallel()

	// All expected outputs verified against live Python implementation on 2026-05-05:
	//   PYTHONPATH=scripts:. python -c 'from czech_utils import parse_month_references; print(parse_month_references("<input>", 2026))'
	tests := []struct {
		name        string
		input       string
		defaultYear int
		want        []string
	}{
		{
			name:        "empty",
			input:       "",
			defaultYear: 2026,
			want:        []string{},
		},
		{
			name:        "numeric plus-split two months full year",
			input:       "11+12/2025",
			defaultYear: 2026,
			want:        []string{"2025-11", "2025-12"},
		},
		{
			name:        "numeric single month full year",
			input:       "1/2026",
			defaultYear: 2026,
			want:        []string{"2026-01"},
		},
		{
			name:        "numeric 2-digit year",
			input:       "01/26",
			defaultYear: 2026,
			want:        []string{"2026-01"},
		},
		{
			name:        "numeric plus-split with 2-digit year",
			input:       "11+12/25",
			defaultYear: 2026,
			want:        []string{"2025-11", "2025-12"},
		},
		{
			name:        "numeric three months sorted",
			input:       "12+1+2/2026",
			defaultYear: 2026,
			want:        []string{"2026-01", "2026-02", "2026-12"},
		},
		{
			name:        "dot pattern",
			input:       "12.2025",
			defaultYear: 2026,
			want:        []string{"2025-12"},
		},
		{
			name:        "dot pattern requires 4-digit year",
			input:       "1.26",
			defaultYear: 2026,
			want:        []string{},
		},
		{
			name:        "standalone month below m10 threshold",
			input:       "leden",
			defaultYear: 2026,
			want:        []string{"2026-01"},
		},
		{
			name:        "standalone month m10 heuristic",
			input:       "prosinec",
			defaultYear: 2026,
			want:        []string{"2025-12"},
		},
		{
			name:        "declension prosince",
			input:       "prosince",
			defaultYear: 2026,
			want:        []string{"2025-12"},
		},
		{
			name:        "declension lednu",
			input:       "lednu",
			defaultYear: 2026,
			want:        []string{"2026-01"},
		},
		{
			name:        "standalone m10 boundary (rijen = October)",
			input:       "rijen",
			defaultYear: 2026,
			want:        []string{"2025-10"},
		},
		{
			name:        "standalone m9 just below boundary (zari = September)",
			input:       "zari",
			defaultYear: 2026,
			want:        []string{"2026-09"},
		},
		{
			name:        "range wrap Nov-Jan",
			input:       "listopad-leden",
			defaultYear: 2026,
			want:        []string{"2025-11", "2025-12", "2026-01"},
		},
		{
			name:        "range wrap starting at October",
			input:       "rijen-leden",
			defaultYear: 2026,
			want:        []string{"2025-10", "2025-11", "2025-12", "2026-01"},
		},
		{
			name:        "range no wrap",
			input:       "unor-kveten",
			defaultYear: 2026,
			want:        []string{"2026-02", "2026-03", "2026-04", "2026-05"},
		},
		{
			name:        "degenerate range same month",
			input:       "leden-leden",
			defaultYear: 2026,
			want:        []string{"2026-01"},
		},
		{
			name:        "range spanning m10 — heuristic does NOT fire for range members",
			input:       "unor-listopad",
			defaultYear: 2026,
			want:        []string{"2026-02", "2026-03", "2026-04", "2026-05", "2026-06", "2026-07", "2026-08", "2026-09", "2026-10", "2026-11"},
		},
		{
			name:        "longest-match alternation cervenec beats cerven",
			input:       "cervenec-srpen",
			defaultYear: 2026,
			want:        []string{"2026-07", "2026-08"},
		},
		{
			name:        "range plus standalone — range excludes, dedup",
			input:       "listopad-leden, prosinec",
			defaultYear: 2026,
			want:        []string{"2025-11", "2025-12", "2026-01"},
		},
		{
			name:        "two standalones no range",
			input:       "prosinec leden",
			defaultYear: 2026,
			want:        []string{"2025-12", "2026-01"},
		},
		{
			name:        "numeric plus range mix",
			input:       "11+12/2025, leden-brezen",
			defaultYear: 2026,
			want:        []string{"2025-11", "2025-12", "2026-01", "2026-02", "2026-03"},
		},
		{
			name:        "dedup across numeric and standalone passes",
			input:       "11+12/25 a listopad",
			defaultYear: 2026,
			want:        []string{"2025-11", "2025-12"},
		},
		{
			name:        "no digits before slash — standalone fires instead",
			input:       "prosince/2025",
			defaultYear: 2026,
			want:        []string{"2025-12"},
		},
		{
			name:        "range with trailing slash-year — numeric fails, range wins",
			input:       "listopad-prosinec/2025",
			defaultYear: 2026,
			want:        []string{"2026-11", "2026-12"},
		},
		{
			name:        "dot pattern only — numeric matches but month out of 1-12 range",
			input:       "01.2026 / 02.2026",
			defaultYear: 2026,
			want:        []string{"2026-01", "2026-02"},
		},
		{
			name:        "leading slash — numeric matches at second slash",
			input:       "/12/2025",
			defaultYear: 2026,
			want:        []string{"2025-12"},
		},
		{
			name:        "uppercase input normalized",
			input:       "PROSINEC",
			defaultYear: 2026,
			want:        []string{"2025-12"},
		},
		{
			name:        "diacritics stripped by Normalize",
			input:       "Žluťoučký prosinec",
			defaultYear: 2026,
			want:        []string{"2025-12"},
		},
		{
			name:        "diacritics in range with spaces around dash",
			input:       "Únor - květen",
			defaultYear: 2026,
			want:        []string{"2026-02", "2026-03", "2026-04", "2026-05"},
		},
		{
			name:        "natural language mixed with numeric and standalone",
			input:       "platba 11/2025 a leden",
			defaultYear: 2026,
			want:        []string{"2025-11", "2026-01"},
		},
		{
			name:        "English month name not recognized",
			input:       "December",
			defaultYear: 2026,
			want:        []string{},
		},
		{
			name:        "duplicate input deduped",
			input:       "11+12/2025 11+12/2025",
			defaultYear: 2026,
			want:        []string{"2025-11", "2025-12"},
		},
		{
			name:        "trailing year without separator ignored",
			input:       "leden 2026",
			defaultYear: 2026,
			want:        []string{"2026-01"},
		},
	}

	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()
			got := ParseMonthReferences(tc.input, tc.defaultYear)
			if got == nil {
				got = []string{}
			}
			if !reflect.DeepEqual(got, tc.want) {
				t.Errorf("ParseMonthReferences(%q, %d)\n  got  %v\n  want %v",
					tc.input, tc.defaultYear, got, tc.want)
			}
		})
	}
}