package model

import (
	"fmt"
	"math"
	"time"
)

// ItemSpec holds mask parameters (from template CLI).
type ItemSpec struct {
	// SizeMM is legacy: square product when width_mm/height_mm are unset.
	SizeMM         float64 `json:"size_mm,omitempty"`
	WidthMM        float64 `json:"width_mm,omitempty"`
	HeightMM       float64 `json:"height_mm,omitempty"`
	CornerRadiusMM float64 `json:"corner_radius_mm,omitempty"`
	BleedMM        float64 `json:"bleed_mm"`
	MarginMM       float64 `json:"margin_mm"`
	PaddingMM      float64 `json:"padding_mm"`
}

// ViewportWidth returns the SVG viewport width used for layout packing.
func (s ItemSpec) ViewportWidth() float64 {
	if s.WidthMM > 0 {
		return s.WidthMM
	}
	return s.SizeMM
}

// ViewportHeight returns the SVG viewport height used for layout packing.
func (s ItemSpec) ViewportHeight() float64 {
	if s.HeightMM > 0 {
		return s.HeightMM
	}
	return s.SizeMM
}

// markLengthMM is crop-mark extension outside the product (must match svgtemplate).
const markLengthMM = 6

// TrimOffsetMM is bleed + margin + crop marks drawn outside the product rect.
func (s ItemSpec) TrimOffsetMM() float64 {
	return s.BleedMM + s.MarginMM + markLengthMM
}

// CanvasWidthMM is the full item SVG width including trim and crop marks.
func (s ItemSpec) CanvasWidthMM() float64 {
	return s.ViewportWidth() + 2*s.TrimOffsetMM()
}

// CanvasHeightMM is the full item SVG height including trim and crop marks.
func (s ItemSpec) CanvasHeightMM() float64 {
	return s.ViewportHeight() + 2*s.TrimOffsetMM()
}

// Normalize fills width/height from legacy size_mm and validates dimensions.
func (s *ItemSpec) Normalize() error {
	if s.WidthMM <= 0 && s.HeightMM <= 0 && s.SizeMM > 0 {
		s.WidthMM = s.SizeMM
		s.HeightMM = s.SizeMM
	}
	if s.WidthMM <= 0 || s.HeightMM <= 0 {
		return fmt.Errorf("width_mm and height_mm must be positive")
	}
	if s.CornerRadiusMM < 0 {
		return fmt.Errorf("corner_radius_mm must be non-negative")
	}
	maxR := math.Min(s.WidthMM, s.HeightMM) / 2
	if s.CornerRadiusMM > maxR {
		return fmt.Errorf("corner_radius_mm must be at most %.2f", maxR)
	}
	return nil
}

// Item is a printable product type (SVG mask) placed on a plate.
type Item struct {
	ID          string    `json:"id"`
	Name        string    `json:"name,omitempty"`
	Spec        ItemSpec  `json:"spec"`
	SVGTemplate string    `json:"svg_template"`
	CreatedAt   time.Time `json:"created_at"`
}

// MetaFilename returns the sidecar metadata path for an SVG basename.
func MetaFilename(svgBasename string) string {
	return svgBasename + ".meta.json"
}