package service

import (
	"math"
	"sort"
	"strings"

	"floorvisualizer/internal/model"
)

type ProductService struct {
	products []model.Product
	config   model.EngineConfig
}

func NewProductService(products []model.Product, config model.EngineConfig) *ProductService {
	if config.MinScore <= 0 {
		config.MinScore = 70
	}
	if config.MaxResults <= 0 {
		config.MaxResults = 10
	}
	return &ProductService{products: products, config: config}
}

func (s *ProductService) AllProducts() []model.Product { return s.products }

func (s *ProductService) FindMatches(source model.Product) []model.MatchResult {
	candidates := make([]model.Product, 0)
	for _, p := range s.products {
		if p.SKU == source.SKU && p.Brand == source.Brand {
			continue
		}
		if p.Brand == source.Brand && p.StyleName == source.StyleName {
			continue
		}
		if p.Category != source.Category {
			continue
		}
		candidates = append(candidates, p)
	}

	// Score all candidates
	allResults := make([]model.MatchResult, 0, len(candidates))
	for _, c := range candidates {
		score, detail := s.score(source, c)
		allResults = append(allResults, model.MatchResult{Product: c, Score: score, Details: detail})
	}
	sort.Slice(allResults, func(i, j int) bool { return allResults[i].Score > allResults[j].Score })

	// Prefer above MinScore, fill remaining with best below
	above := make([]model.MatchResult, 0)
	below := make([]model.MatchResult, 0)
	for _, r := range allResults {
		if r.Score >= s.config.MinScore {
			above = append(above, r)
		} else {
			below = append(below, r)
		}
	}

	// Always return at least 5 (or as many as available), filling gaps with best below-70
	combined := above
	need := s.config.MaxResults - len(combined)
	for i := 0; i < need && i < len(below); i++ {
		combined = append(combined, below[i])
	}

	if len(combined) == 0 {
		return nil
	}

	const maxPerBrand = 3
	brandCount := map[string]int{}
	diverse := make([]model.MatchResult, 0, s.config.MaxResults)
	for _, r := range combined {
		if brandCount[r.Product.Brand] < maxPerBrand {
			brandCount[r.Product.Brand]++
			diverse = append(diverse, r)
		}
		if len(diverse) >= s.config.MaxResults {
			break
		}
	}
	return diverse
}

func (s *ProductService) score(source, candidate model.Product) (float64, model.ScoreDetail) {
	w := s.config
	colorS := scoreColor(source.ColorTone, candidate.ColorTone)
	finishS := scoreFinish(source.Finish, candidate.Finish)
	visualScore := clamp((colorS*0.7 + finishS*0.3) * 100)

	materialScore := 0.0
	if normalizeMaterial(source.Material) == normalizeMaterial(candidate.Material) {
		materialScore = 100
	} else if sameMaterialFamily(source.Material, candidate.Material) {
		materialScore = 50
	}

	priceScore := scorePrice(source, candidate)
	categoryScore := 100.0

	hasPrice := source.PricePerSqft > 0 && candidate.PricePerSqft > 0 &&
		source.PricePerSqft != 4.99 && candidate.PricePerSqft != 4.99 &&
		source.PriceSource != "pending_review" && candidate.PriceSource != "pending_review"

	weightV, weightM, weightP, weightC := w.WeightVisual, w.WeightMaterial, w.WeightPrice, w.WeightCategory
	if !hasPrice {
		redist := weightP / 3
		weightV += redist * 2
		weightM += redist
		weightP = 0
	}

	total := (visualScore*weightV + materialScore*weightM + priceScore*weightP + categoryScore*weightC) / 100.0

	groupPenalty := 0.0
	if source.GroupName != "" && candidate.GroupName != "" && source.GroupName == candidate.GroupName {
		if priceTierGap(source.PriceTier, candidate.PriceTier) >= 2 {
			groupPenalty = -10
		} else {
			groupPenalty = -20
		}
		total += groupPenalty
	}

	detail := model.ScoreDetail{
		Visual:       round(visualScore),
		Material:     round(materialScore),
		Price:        round(priceScore),
		Category:     round(categoryScore),
		GroupPenalty: groupPenalty,
	}
	return round(total), detail
}

// ── Scoring helpers ─────────────────────────────────────────

func scoreColor(source, candidate string) float64 {
	if source == "" || candidate == "" { return 0.5 }
	if source == candidate { return 1.0 }
	groups := [][]string{
		{"Light Gray", "Off White", "Taupe"},
		{"Dark Brown", "Black Walnut", "Taupe"},
		{"Natural Oak", "Warm Honey", "Taupe"},
		{"Cherry", "Dark Brown"},
		{"Green", "Blue"},
	}
	for _, g := range groups {
		if contains(g, source) && contains(g, candidate) { return 0.6 }
	}
	return 0.1
}

func scoreFinish(source, candidate string) float64 {
	if source == "" || candidate == "" { return 0.5 }
	if source == candidate { return 1.0 }
	if (source == "Matte" && candidate == "Textured") || (source == "Textured" && candidate == "Matte") {
		return 0.6
	}
	return 0.2
}

func scorePrice(source model.Product, candidate model.Product) float64 {
	sp, cp := source.PricePerSqft, candidate.PricePerSqft
	ss, cs := source.PriceSource, candidate.PriceSource

	if ss == "pending_review" || cs == "pending_review" || ss == "estimated" || cs == "estimated" { return 50 }
	if cp <= 0 { return 50 }

	// If source has specs with different prices, use the closest-matching one
	if len(source.Specs) > 1 {
		bestDist := math.Abs(sp - cp)
		for _, s := range source.Specs {
			if s.PricePerSqft > 0 {
				d := math.Abs(s.PricePerSqft - cp)
				if d < bestDist {
					bestDist = d
					sp = s.PricePerSqft
				}
			}
		}
	}

	if sp <= 0 { return 50 }
	maxP := math.Max(sp, cp)
	if maxP == 0 { return 50 }
	return clamp(100 * (1 - math.Abs(sp-cp)/maxP))
}

func normalizeMaterial(m string) string {
	for _, prefix := range []string{"Porcelain"} {
		if len(m) >= len(prefix) && m[:len(prefix)] == prefix { return prefix }
	}
	lower := strings.ToLower(m)
	if strings.Contains(lower, "rigid core") { return "Rigid Core" }
	if strings.Contains(lower, "luxury vinyl") || strings.Contains(lower, "vinyl") { return "LVT" }
	if strings.Contains(lower, "laminate") { return "Laminate" }
	return m
}

func sameMaterialFamily(a, b string) bool {
	aN, bN := normalizeMaterial(a), normalizeMaterial(b)
	woods := []string{"Oak", "Maple", "Hickory", "Walnut", "Cherry Wood", "Birch", "Pine", "Ash", "Acacia", "Elm", "Teak", "Bamboo", "Mahogany", "Chestnut", "Rosewood", "Ebony"}
	stones := []string{"Porcelain", "Stone Texture", "Marble", "Travertine", "Slate", "Cement"}
	vinyls := []string{"SPC", "LVT", "PVC", "Rigid Core", "Luxury Vinyl", "Vinyl"}
	if contains(woods, aN) && contains(woods, bN) { return true }
	if contains(stones, aN) && contains(stones, bN) { return true }
	if contains(vinyls, aN) && contains(vinyls, bN) { return true }
	return false
}

func priceTierGap(a, b string) int {
	rank := map[string]int{"": 0, "Budget/Value": 1, "Mid-Range": 2, "Upper Mid-Range": 3, "Premium": 4}
	ra, rb := rank[a], rank[b]
	diff := ra - rb
	if diff < 0 { diff = -diff }
	return diff
}

func round(v float64) float64 { return math.Round(v*10) / 10 }
func clamp(v float64) float64 { return math.Max(0, math.Min(100, v)) }

func contains(slice []string, item string) bool {
	for _, s := range slice {
		if s == item { return true }
	}
	return false
}