package embedding

import (
	"reflect"
	"testing"
)

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

	ix := NewIndex[int]()
	ix.Add("go is a programming language", 1)
	ix.Add("rust is a systems language", 2)
	ix.Add("python is great", 3)

	hits := ix.Search("language")
	if len(hits) != 2 {
		t.Fatalf("Search(\"language\") returned %d hits, want 2", len(hits))
	}
	if got := []int{hits[0].ID, hits[1].ID}; !reflect.DeepEqual(got, []int{1, 2}) {
		t.Errorf("top hits = %v, want [1 2]", got)
	}
}

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

	ix := NewIndex[int]()
	ix.Add("cat cat cat dog", 1)
	ix.Add("dog dog cat", 2)

	hits := ix.Search("cat")
	if len(hits) != 2 {
		t.Fatalf("Search(\"cat\") returned %d hits, want 2", len(hits))
	}
	// Doc 1 has cat 3 times, doc 2 once, so doc 1 ranks higher.
	if hits[0].ID != 1 {
		t.Errorf("top hit = %d, want 1 (higher tf)", hits[0].ID)
	}
	if hits[1].ID != 2 {
		t.Errorf("second hit = %d, want 2", hits[1].ID)
	}
}

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

	ix := NewIndex[int]()
	ix.Add("the red fox", 1)
	ix.Add("the blue whale", 2)
	ix.Add("a red car", 3)

	hits := ix.Search("red fox")
	if len(hits) != 2 {
		t.Fatalf("Search(\"red fox\") returned %d hits, want 2", len(hits))
	}
	// Doc 1 matches both terms (higher), doc 3 only 'red'.
	if hits[0].ID != 1 || hits[1].ID != 3 {
		t.Fatalf("hits = %v, want docs [1 3]", hits)
	}
}

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

	ix := NewIndex[int]()
	ix.Add("hello world", 1)

	if got := ix.Search(""); len(got) != 0 {
		t.Errorf("Search(\"\") returned %d hits, want 0", len(got))
	}
	if got := ix.Search("   "); len(got) != 0 {
		t.Errorf("Search(\"   \") returned %d hits, want 0", len(got))
	}
}

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

	ix := NewIndex[int]()
	ix.Add("hello world", 1)

	if got := ix.Search("unrelatedterm"); len(got) != 0 {
		t.Errorf("Search(unrelatedterm) returned %d hits, want 0", len(got))
	}
}

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

	ix := NewIndex[int]()
	ix.Add("hello world", 1)
	ix.Add("goodbye world", 1) // re-add same id

	if got := ix.Search("hello"); len(got) != 0 {
		t.Errorf("Search(\"hello\") after re-add returned %d hits, want 0", len(got))
	}
	if got := ix.Search("world"); len(got) != 1 {
		t.Errorf("Search(\"world\") after re-add returned %d hits, want 1", len(got))
	}
}

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

	ix := NewIndex[string]()
	ix.Add("night sky blue", "moon")
	ix.Add("ocean blue water", "sea")

	hits := ix.Search("blue")
	if len(hits) != 2 {
		t.Fatalf("Search(\"blue\") returned %d hits, want 2", len(hits))
	}
	if hits[0].ID != "moon" || hits[1].ID != "sea" {
		t.Errorf("hits = %v, want [moon sea]", hits)
	}
}