package ice

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

func TestCosineSimilarity(t *testing.T) {
    tests := []struct {
        name string
        a, b []float32
        want float32
        tol  float32
    }{
        {
            name: "identical vectors",
            a:    []float32{1, 2, 3},
            b:    []float32{1, 2, 3},
            want: 1.0,
            tol:  1e-6,
        },
        {
            name: "orthogonal vectors",
            a:    []float32{1, 0},
            b:    []float32{0, 1},
            want: 0.0,
            tol:  1e-6,
        },
        {
            name: "opposite vectors",
            a:    []float32{1, 0},
            b:    []float32{-1, 0},
            want: -1.0,
            tol:  1e-6,
        },
        {
            name: "different lengths returns 0",
            a:    []float32{1, 0},
            b:    []float32{1, 0, 0},
            want: 0,
            tol:  0,
        },
        {
            name: "zero vector returns 0",
            a:    []float32{0, 0},
            b:    []float32{1, 1},
            want: 0,
            tol:  0,
        },
        {
            name: "known value with tolerance",
            a:    []float32{1, 1},
            b:    []float32{1, 0},
            // 1/(sqrt(2)*1) ≈ 0.7071
            want: float32(1.0 / math.Sqrt(2)),
            tol:  1e-4,
        },
        {
            name: "empty vectors",
            a:    []float32{},
            b:    []float32{},
            want: 0,
            tol:  0,
        },
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            got := cosineSimilarity(tt.a, tt.b)
            diff := got - tt.want
            if diff < 0 {
                diff = -diff
            }
            if diff > tt.tol {
                t.Errorf("cosineSimilarity(%v, %v) = %f, want %f (±%f)",
                    tt.a, tt.b, got, tt.want, tt.tol)
            }
        })
    }
}

func TestStore_Add_And_Count(t *testing.T) {
    dir := t.TempDir()
    path := filepath.Join(dir, "store.json")

    s := NewStore(path)

    if s.Count() != 0 {
        t.Fatalf("new store Count = %d, want 0", s.Count())
    }

    id1, err := s.Add("sess1", "user", "hello", []float32{1, 0, 0}, 0)
    if err != nil {
        t.Fatalf("Add returned error: %v", err)
    }
    if id1 != 1 {
        t.Errorf("first Add returned id=%d, want 1", id1)
    }
    if s.Count() != 1 {
        t.Errorf("Count after first Add = %d, want 1", s.Count())
    }

    id2, err := s.Add("sess1", "assistant", "world", []float32{0, 1, 0}, 1)
    if err != nil {
        t.Fatalf("Add returned error: %v", err)
    }
    if id2 != 2 {
        t.Errorf("second Add returned id=%d, want 2", id2)
    }
    if s.Count() != 2 {
        t.Errorf("Count after second Add = %d, want 2", s.Count())
    }
}

func TestStore_Search(t *testing.T) {
    dir := t.TempDir()
    path := filepath.Join(dir, "store.json")
    s := NewStore(path)

    // Add entries with known embeddings.
    s.Add("sess1", "user", "entry A", []float32{1, 0, 0}, 0)
    s.Add("sess1", "user", "entry B", []float32{0, 1, 0}, 1)
    s.Add("sess2", "user", "entry C", []float32{0.9, 0.1, 0}, 0)
    s.Add("sess2", "user", "entry D", []float32{0, 0, 1}, 1) // orthogonal to query

    t.Run("similarity filtering and sorting", func(t *testing.T) {
        // Query similar to entries A and C, exclude no session.
        results := s.Search([]float32{1, 0, 0}, "", 10)
        if len(results) == 0 {
            t.Fatal("expected results, got 0")
        }
        // Entry A should be highest (identical to query).
        if results[0].Entry.Content != "entry A" {
            t.Errorf("top result = %q, want 'entry A'", results[0].Entry.Content)
        }
    })

    t.Run("session exclusion", func(t *testing.T) {
        results := s.Search([]float32{1, 0, 0}, "sess1", 10)
        for _, r := range results {
            if r.Entry.SessionID == "sess1" {
                t.Errorf("excluded session sess1 should not appear in results")
            }
        }
    })

    t.Run("min threshold 0.3", func(t *testing.T) {
        // Entry D: [0,0,1] is orthogonal to [1,0,0] → similarity 0.
        results := s.Search([]float32{1, 0, 0}, "", 10)
        for _, r := range results {
            if r.Score < minSimilarityThreshold {
                t.Errorf("result %q has score %f below threshold %f",
                    r.Entry.Content, r.Score, minSimilarityThreshold)
            }
        }
    })

    t.Run("topK limit", func(t *testing.T) {
        results := s.Search([]float32{1, 0, 0}, "", 1)
        if len(results) > 1 {
            t.Errorf("topK=1 but got %d results", len(results))
        }
    })

    t.Run("empty store returns nil", func(t *testing.T) {
        emptyPath := filepath.Join(dir, "empty.json")
        empty := NewStore(emptyPath)
        results := empty.Search([]float32{1, 0}, "", 5)
        if results != nil {
            t.Errorf("empty store search should return nil, got %v", results)
        }
    })

    t.Run("empty query embedding returns nil", func(t *testing.T) {
        results := s.Search([]float32{}, "", 5)
        if results != nil {
            t.Errorf("empty query should return nil, got %v", results)
        }
    })
}

func TestStore_Flush_Persistence(t *testing.T) {
    t.Run("round trip", func(t *testing.T) {
        dir := t.TempDir()
        path := filepath.Join(dir, "store.json")

        s1 := NewStore(path)
        s1.Add("sess1", "user", "hello", []float32{1, 0}, 0)
        s1.Add("sess1", "assistant", "world", []float32{0, 1}, 1)

        if err := s1.Flush(); err != nil {
            t.Fatalf("Flush: %v", err)
        }

        // Reload from same path.
        s2 := NewStore(path)
        if s2.Count() != 2 {
            t.Errorf("reloaded store Count = %d, want 2", s2.Count())
        }
    })

    t.Run("corrupt JSON recovery", func(t *testing.T) {
        dir := t.TempDir()
        path := filepath.Join(dir, "store.json")

        // Write corrupt JSON.
        os.WriteFile(path, []byte("not valid json{{{"), 0o644)

        s := NewStore(path)
        if s.Count() != 0 {
            t.Errorf("corrupt store Count = %d, want 0", s.Count())
        }
    })

    t.Run("nextID restoration", func(t *testing.T) {
        dir := t.TempDir()
        path := filepath.Join(dir, "store.json")

        s1 := NewStore(path)
        s1.Add("sess1", "user", "first", []float32{1}, 0)
        s1.Add("sess1", "user", "second", []float32{1}, 1)
        s1.Flush()

        s2 := NewStore(path)
        id, _ := s2.Add("sess1", "user", "third", []float32{1}, 2)
        if id != 3 {
            t.Errorf("continued id = %d, want 3", id)
        }
    })
}