libgofunc/canvas.go

package libgofunc

import (
	"strconv"
	"strings"

	"github.com/fogleman/gg"
	"golang.org/x/image/font"
	"golang.org/x/net/html"
)

// -------------------- STYLE --------------------
type Style struct {
	PaddingLeft   float64
	PaddingRight  float64
	PaddingTop    float64
	PaddingBottom float64
	FontSize      float64
	Width         float64
	Height        float64
	TextAlign     string
	VerticalAlign string
	Border        float64
}

func parseStyle(styleStr string) Style {
	style := Style{
		FontSize:      16,
		TextAlign:     "left",
		VerticalAlign: "top",
	}

	parts := strings.Split(styleStr, ";")
	for _, p := range parts {
		kv := strings.SplitN(strings.TrimSpace(p), ":", 2)
		if len(kv) != 2 {
			continue
		}
		key := strings.TrimSpace(kv[0])
		val := strings.TrimSpace(kv[1])

		switch key {
		case "padding":
			v := parsePx(val)
			style.PaddingLeft, style.PaddingRight, style.PaddingTop, style.PaddingBottom = v, v, v, v
		case "padding-left":
			v := parsePx(val)
			style.PaddingLeft = v
		case "padding-right":
			v := parsePx(val)
			style.PaddingRight = v
		case "padding-top":
			v := parsePx(val)
			style.PaddingTop = v
		case "padding-bottom":
			v := parsePx(val)
			style.PaddingBottom = v
		case "font-size":
			style.FontSize = parsePx(val)
		case "width":
			style.Width = parsePx(val)
		case "height":
			style.Height = parsePx(val)
		case "text-align":
			style.TextAlign = val
		case "vertical-align":
			style.VerticalAlign = val
		case "border":
			style.Border = parsePx(val)
		}
	}
	return style
}

func parsePx(v string) float64 {
	v = strings.ReplaceAll(v, "px", "")
	f, _ := strconv.ParseFloat(v, 64)
	return f
}

// -------------------- NODE --------------------
type Node struct {
	Tag      string
	Text     string
	Attr     map[string]string
	Style    Style
	Children []*Node
}

func (n Node) getSrc() string {
	for k, v := range n.Attr {
		if k == "src" {
			return v
		}
	}
	return ""
}

func (n Node) getHeight() int {
	return int(n.Style.Height)
}

func BuildTree(n *html.Node, canvasWidth int, dc *gg.Context, face *font.Face) (*Node, int) {
	if n.Type != html.ElementNode {
		return nil, 0
	}

	text := ""
	if n.Data == "h1" || n.Data == "h2" || n.Data == "h3" ||
		n.Data == "p" || n.Data == "td" || n.Data == "th" ||
		n.Type == html.TextNode {
		text = getText(n)
	}

	node := &Node{
		Tag:  n.Data,
		Text: text,
		Attr: map[string]string{},
	}

	for _, a := range n.Attr {
		node.Attr[a.Key] = a.Val
	}

	if s, ok := node.Attr["style"]; ok {
		node.Style = parseStyle(s)
	}
	xPadding := node.Style.PaddingLeft + node.Style.PaddingRight
	yPadding := node.Style.PaddingTop + node.Style.PaddingBottom
	fontSize := node.Style.FontSize
	h := nodeHeight(n, dc, canvasWidth, int(xPadding), int(yPadding),
		face, fontSize, node.getHeight())
	for c := n.FirstChild; c != nil; c = c.NextSibling {
		child, ch := BuildTree(c, canvasWidth, dc, face)
		if child != nil {
			node.Children = append(node.Children, child)
		}
		h += ch
	}
	return node, h
}