package recommendation

import (
	"context"
	"math"
	"testing"
	"time"

	"github.com/jackc/pgx/v5/pgtype"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
)

func uuidN(n byte) pgtype.UUID {
	return pgtype.UUID{Bytes: [16]byte{15: n}, Valid: true}
}

func strPtr(s string) *string { return &s }

func TestTasteProfile_Match(t *testing.T) {
	loved := uuidN(1)
	disliked := uuidN(2)
	unknown := uuidN(3)
	p := TasteProfile{
		artists: map[pgtype.UUID]float64{loved: 8.0, disliked: -8.0},
		tags:    map[string]float64{"Jazz": 6.0, "Noise": -6.0},
	}

	if m := p.Match(loved, strPtr("Jazz")); m <= 0.5 {
		t.Errorf("loved artist + loved tag = %.3f, want strongly positive", m)
	}
	if m := p.Match(disliked, strPtr("Noise")); m >= -0.5 {
		t.Errorf("disliked artist + disliked tag = %.3f, want strongly negative", m)
	}
	if m := p.Match(unknown, nil); m != 0 {
		t.Errorf("unknown artist, no genre = %.3f, want 0", m)
	}
	// Artist dominates (0.7 share): loved artist with an unknown tag is still
	// clearly positive.
	if m := p.Match(loved, strPtr("Unheard")); m <= 0 {
		t.Errorf("loved artist + unknown tag = %.3f, want positive", m)
	}
	// Output stays within [-1, 1] even with saturated inputs.
	for _, a := range []pgtype.UUID{loved, disliked, unknown} {
		m := p.Match(a, strPtr("Jazz"))
		if m < -1 || m > 1 {
			t.Errorf("Match out of [-1,1]: %.3f", m)
		}
	}
}

func TestTasteProfile_EmptyIsNeutral(t *testing.T) {
	var p TasteProfile // zero value: nil maps
	if m := p.Match(uuidN(1), strPtr("Jazz")); m != 0 {
		t.Errorf("empty profile Match = %.3f, want 0 (cold start neutral)", m)
	}
}

func TestScore_TasteTermAddsAndSubtracts(t *testing.T) {
	now := time.Now()
	zeroJitter := func() float64 { return 0.5 } // (0.5*2-1)=0 with any magnitude
	w := ScoringWeights{TasteWeight: 2.0}       // all other weights 0

	pos := Score(ScoringInputs{TasteMatchScore: 1.0}, w, now, zeroJitter)
	if !almostEq(pos, 2.0) {
		t.Errorf("positive taste: Score = %.3f, want 2.0", pos)
	}
	neg := Score(ScoringInputs{TasteMatchScore: -1.0}, w, now, zeroJitter)
	if !almostEq(neg, -2.0) {
		t.Errorf("negative taste: Score = %.3f, want -2.0 (demotes)", neg)
	}
	off := Score(ScoringInputs{TasteMatchScore: 1.0}, ScoringWeights{}, now, zeroJitter)
	if !almostEq(off, 0.0) {
		t.Errorf("TasteWeight 0: Score = %.3f, want 0 (no effect)", off)
	}
}

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

// TestLoadTasteProfile_RoundTrip seeds taste_profile rows and verifies the
// reader hydrates them into a profile that scores a matching track positively.
func TestLoadTasteProfile_RoundTrip(t *testing.T) {
	pool := newPool(t)
	ctx := context.Background()
	u := seedUser(t, pool, "taste-rt")
	art := seedArtist(t, pool, "Loved Artist", "")

	if _, err := pool.Exec(ctx,
		`INSERT INTO taste_profile_artists (user_id, artist_id, weight) VALUES ($1, $2, $3)`,
		u.ID, art.ID, 8.0); err != nil {
		t.Fatalf("seed taste artist: %v", err)
	}
	if _, err := pool.Exec(ctx,
		`INSERT INTO taste_profile_tags (user_id, tag, weight) VALUES ($1, $2, $3)`,
		u.ID, "Jazz", 6.0); err != nil {
		t.Fatalf("seed taste tag: %v", err)
	}

	p, err := LoadTasteProfile(ctx, dbq.New(pool), u.ID)
	if err != nil {
		t.Fatalf("load: %v", err)
	}
	if m := p.Match(art.ID, strPtr("Jazz")); m <= 0.5 {
		t.Errorf("round-trip Match = %.3f, want strongly positive", m)
	}
	if m := p.Match(uuidN(9), nil); m != 0 {
		t.Errorf("absent artist Match = %.3f, want 0", m)
	}
}
