moteva/server/internal/application/project_thumbnail.go

package application

import (
	"encoding/base64"
	"encoding/json"
	"math"
	"strings"

	"img_infinite_canvas/internal/domain/design"
)

const projectCanvasPreviewPrefix = "CANVASPREVIEW://"

type projectCanvasPreview struct {
	Bounds projectPreviewBounds `json:"bounds"`
	Nodes  []projectPreviewNode `json:"nodes"`
}

type projectPreviewBounds struct {
	X      float64 `json:"x"`
	Y      float64 `json:"y"`
	Width  float64 `json:"width"`
	Height float64 `json:"height"`
}

type projectPreviewNode struct {
	Type           string  `json:"type"`
	Title          string  `json:"title"`
	X              float64 `json:"x"`
	Y              float64 `json:"y"`
	Width          float64 `json:"width"`
	Height         float64 `json:"height"`
	Content        string  `json:"content,omitempty"`
	Tone           string  `json:"tone,omitempty"`
	LayerRole      string  `json:"layerRole,omitempty"`
	FillColor      string  `json:"fillColor,omitempty"`
	StrokeColor    string  `json:"strokeColor,omitempty"`
	StrokeWidth    float64 `json:"strokeWidth,omitempty"`
	Color          string  `json:"color,omitempty"`
	FontSize       float64 `json:"fontSize,omitempty"`
	FontFamily     string  `json:"fontFamily,omitempty"`
	FontWeight     string  `json:"fontWeight,omitempty"`
	TextAlign      string  `json:"textAlign,omitempty"`
	LineHeight     float64 `json:"lineHeight,omitempty"`
	LetterSpacing  float64 `json:"letterSpacing,omitempty"`
	TextDecoration string  `json:"textDecoration,omitempty"`
	TextTransform  string  `json:"textTransform,omitempty"`
	Opacity        float64 `json:"opacity,omitempty"`
}

func projectThumbnail(project design.Project) string {
	if thumbnail := canvasPreviewThumbnail(project.Nodes); thumbnail != "" {
		return thumbnail
	}
	if thumbnail := mainCanvasPreviewImage(project.Nodes); thumbnail != "" {
		return thumbnail
	}
	return inferThumbnail(project.Brief)
}

func canvasPreviewThumbnail(nodes []design.Node) string {
	previewNodes := canvasPreviewNodes(nodes)
	if len(previewNodes) == 0 {
		return ""
	}

	bounds := previewBounds(previewNodes)
	payload, err := json.Marshal(projectCanvasPreview{
		Bounds: bounds,
		Nodes:  previewNodes,
	})
	if err != nil {
		return ""
	}
	return projectCanvasPreviewPrefix + base64.StdEncoding.EncodeToString(payload)
}

func canvasPreviewNodes(nodes []design.Node) []projectPreviewNode {
	items := make([]projectPreviewNode, 0, len(nodes))
	for _, node := range nodes {
		if !isPreviewableNode(node) {
			continue
		}
		content := strings.TrimSpace(node.Content)
		if node.Type == design.NodeTypeFrame && !isGeneratedImageContent(content) {
			content = ""
		}
		items = append(items, projectPreviewNode{
			Type:           string(node.Type),
			Title:          strings.TrimSpace(node.Title),
			X:              node.X,
			Y:              node.Y,
			Width:          math.Max(1, node.Width),
			Height:         math.Max(1, node.Height),
			Content:        content,
			Tone:           strings.TrimSpace(node.Tone),
			LayerRole:      strings.TrimSpace(node.LayerRole),
			FillColor:      strings.TrimSpace(node.FillColor),
			StrokeColor:    strings.TrimSpace(node.StrokeColor),
			StrokeWidth:    node.StrokeWidth,
			Color:          strings.TrimSpace(node.Color),
			FontSize:       node.FontSize,
			FontFamily:     strings.TrimSpace(node.FontFamily),
			FontWeight:     strings.TrimSpace(node.FontWeight),
			TextAlign:      strings.TrimSpace(node.TextAlign),
			LineHeight:     node.LineHeight,
			LetterSpacing:  node.LetterSpacing,
			TextDecoration: strings.TrimSpace(node.TextDecoration),
			TextTransform:  strings.TrimSpace(node.TextTransform),
			Opacity:        node.Opacity,
		})
	}
	if len(items) > 28 {
		items = items[len(items)-28:]
	}
	return items
}

func isPreviewableNode(node design.Node) bool {
	if node.Status == "generating" || node.Status == "error" || node.LayerRole == "pen-stroke" {
		return false
	}
	if node.Width <= 0 || node.Height <= 0 {
		return false
	}
	switch node.Type {
	case design.NodeTypeImage:
		content := strings.TrimSpace(node.Content)
		return content != "" && !strings.HasPrefix(content, "data:image/") && isGeneratedImageContent(content)
	case design.NodeTypeFrame, design.NodeTypeText:
		return true
	default:
		return false
	}
}

func previewBounds(nodes []projectPreviewNode) projectPreviewBounds {
	minX := math.Inf(1)
	minY := math.Inf(1)
	maxX := math.Inf(-1)
	maxY := math.Inf(-1)
	for _, node := range nodes {
		minX = math.Min(minX, node.X)
		minY = math.Min(minY, node.Y)
		maxX = math.Max(maxX, node.X+node.Width)
		maxY = math.Max(maxY, node.Y+node.Height)
	}
	if math.IsInf(minX, 0) || math.IsInf(minY, 0) || math.IsInf(maxX, 0) || math.IsInf(maxY, 0) {
		return projectPreviewBounds{Width: 1, Height: 1}
	}
	width := math.Max(1, maxX-minX)
	height := math.Max(1, maxY-minY)
	padding := math.Max(24, math.Min(width, height)*0.06)
	return projectPreviewBounds{
		X:      minX - padding,
		Y:      minY - padding,
		Width:  width + padding*2,
		Height: height + padding*2,
	}
}