package cmd

import (
	"math"
	"os"
	"path/filepath"
	"testing"
)

func writeFixture(t *testing.T, content string) string {
	t.Helper()
	path := filepath.Join(t.TempDir(), "fixture.json")
	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
		t.Fatal(err)
	}
	return path
}

func TestLoadFixture_Valid(t *testing.T) {
	path := writeFixture(t, `{
		"description": "test",
		"top": 5,
		"queries": [
			{"id": "q1", "query": "hello", "relevant": [{"document_id": 7}]}
		]
	}`)
	fx, err := loadFixture(path)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if fx.Top != 5 || len(fx.Queries) != 1 || fx.Queries[0].Relevant[0].DocumentID != 7 {
		t.Errorf("fixture parsed incorrectly: %+v", fx)
	}
}

func TestLoadFixture_RejectsEmptyRelevant(t *testing.T) {
	path := writeFixture(t, `{"queries": [{"query": "hello", "relevant": []}]}`)
	if _, err := loadFixture(path); err == nil {
		t.Error("expected error for query with no relevant selectors")
	}
}

func TestLoadFixture_RejectsMultiFieldSelector(t *testing.T) {
	path := writeFixture(t, `{"queries": [
		{"query": "hello", "relevant": [{"document_id": 1, "source_path": "/x"}]}
	]}`)
	if _, err := loadFixture(path); err == nil {
		t.Error("expected error for selector with two fields set")
	}
}

func TestSelectorMatching(t *testing.T) {
	doc := benchDoc{DocumentID: 42, Title: "M38T Owner's Manual", SourcePath: "/data/m38t.pdf"}

	cases := []struct {
		name string
		sel  benchSelector
		want bool
	}{
		{"document_id match", benchSelector{DocumentID: 42}, true},
		{"document_id miss", benchSelector{DocumentID: 43}, false},
		{"source_path match", benchSelector{SourcePath: "/data/m38t.pdf"}, true},
		{"source_path miss", benchSelector{SourcePath: "/data/other.pdf"}, false},
		{"title_contains case-insensitive", benchSelector{TitleContains: "m38t owner"}, true},
		{"title_contains miss", benchSelector{TitleContains: "workshop"}, false},
	}
	for _, tc := range cases {
		if got := tc.sel.matches(doc); got != tc.want {
			t.Errorf("%s: got %v, want %v", tc.name, got, tc.want)
		}
	}
}

func TestDedupeByDocument(t *testing.T) {
	docs := []benchDoc{
		{DocumentID: 1, Title: "a"},
		{DocumentID: 2, Title: "b"},
		{DocumentID: 1, Title: "a-again"},
		{DocumentID: 3, Title: "c"},
	}
	out := dedupeByDocument(docs)
	if len(out) != 3 || out[0].DocumentID != 1 || out[1].DocumentID != 2 || out[2].DocumentID != 3 {
		t.Errorf("dedupe failed: %+v", out)
	}
	if out[0].Title != "a" {
		t.Errorf("dedupe must keep first (best-ranked) occurrence, got %q", out[0].Title)
	}
}

func approxEqual(a, b float64) bool {
	return math.Abs(a-b) < 1e-9
}

func TestScoreQuery_HandComputed(t *testing.T) {
	// Ranked docs: 10, 20, 30, 40. Relevant: 20 and 40.
	ranked := []benchDoc{
		{DocumentID: 10}, {DocumentID: 20}, {DocumentID: 30}, {DocumentID: 40},
	}
	relevant := []benchSelector{{DocumentID: 20}, {DocumentID: 40}}

	p, r, m := scoreQuery(ranked, relevant)
	if !approxEqual(p, 0.5) { // 2 of 4 returned docs are relevant
		t.Errorf("precision: got %v, want 0.5", p)
	}
	if !approxEqual(r, 1.0) { // both relevant docs found
		t.Errorf("recall: got %v, want 1.0", r)
	}
	if !approxEqual(m, 0.5) { // first relevant doc at rank 2
		t.Errorf("mrr: got %v, want 0.5", m)
	}
}

func TestScoreQuery_NoMatches(t *testing.T) {
	ranked := []benchDoc{{DocumentID: 1}}
	relevant := []benchSelector{{DocumentID: 99}}
	p, r, m := scoreQuery(ranked, relevant)
	if p != 0 || r != 0 || m != 0 {
		t.Errorf("expected all-zero metrics, got p=%v r=%v mrr=%v", p, r, m)
	}
}

func TestScoreQuery_PartialRecall(t *testing.T) {
	// Only one of three relevant docs returned, at rank 1.
	ranked := []benchDoc{{DocumentID: 5}, {DocumentID: 6}}
	relevant := []benchSelector{{DocumentID: 5}, {DocumentID: 7}, {DocumentID: 8}}
	p, r, m := scoreQuery(ranked, relevant)
	if !approxEqual(p, 0.5) {
		t.Errorf("precision: got %v, want 0.5", p)
	}
	if !approxEqual(r, 1.0/3.0) {
		t.Errorf("recall: got %v, want 1/3", r)
	}
	if !approxEqual(m, 1.0) {
		t.Errorf("mrr: got %v, want 1.0", m)
	}
}

func TestScoreQuery_EmptyResults(t *testing.T) {
	p, r, m := scoreQuery(nil, []benchSelector{{DocumentID: 1}})
	if p != 0 || r != 0 || m != 0 {
		t.Errorf("expected zeros for empty results, got p=%v r=%v mrr=%v", p, r, m)
	}
}