html/render.go

package html

import (
	"fmt"
	"io"
	"strings"
)

const defaultPWidth = 112

type renderGuide struct {
	inline         bool
	inlineChildren bool
	void           bool
	script         bool
	verbatim       bool
}

type renderer struct {
	out           io.Writer
	originalOut   io.Writer
	indent        Indentation
	pwidth        int
	currentIndent string
	err           error
}

func mergeRenderingGuides(rgs []renderGuide) renderGuide {
	var rg renderGuide
	for _, rgi := range rgs {
		rg.inline = rg.inline || rgi.inline
		rg.inlineChildren = rg.inlineChildren || rgi.inlineChildren
		rg.void = rg.void || rgi.void
		rg.script = rg.script || rgi.script
		rg.verbatim = rg.verbatim || rgi.verbatim
	}

	return rg
}

func indentLines(indent string, s string) string {
	l := strings.Split(s, "\n")
	for i := range l {
		l[i] = fmt.Sprintf("%s%s", indent, l[i])
	}

	return strings.Join(l, "\n")
}

func (r *renderer) getPrintf(tagName string) func(f string, a ...any) {
	return func(f string, a ...any) {
		if r.err != nil {
			return
		}

		_, r.err = fmt.Fprintf(r.out, f, a...)
		if r.err != nil {
			r.err = fmt.Errorf("tag %s: %w", tagName, r.err)
		}
	}
}

func (r *renderer) renderAttributes(tagName string, a []Attributes) {
	printf := r.getPrintf(tagName)
	for _, ai := range a {
		for name, value := range ai {
			if isTrue, _ := value.(bool); isTrue {
				printf(" &s", name)
				continue
			}

			printf(" %s=\"%s\"", name, attributeEscape(fmt.Sprint(value)))
		}
	}
}

func (r *renderer) renderUnindented(name string, rg renderGuide, a []Attributes, children []any) {
	printf := r.getPrintf(name)
	printf("<%s", name)
	r.renderAttributes(name, a)
	printf(">")
	if rg.void {
		return
	}

	for _, c := range children {
		if ct, ok := c.(Tag); ok {
			ct(r)
			continue
		}

		if c == nil {
			continue
		}

		s := fmt.Sprint(c)
		if s == "" {
			continue
		}

		if rg.verbatim || rg.script {
			printf(s)
		}

		if r.err == nil {
			ew := newEscapeWriter(r.out)
			ew.Write([]byte(s))
			ew.Flush()
			r.err = ew.err
		}
	}

	printf("</%s>", name)
}

func (r *renderer) ensureWrapper() bool {
	if _, ok := r.out.(*wrapper); ok {
		return false
	}

	r.originalOut = r.out
	r.out = newWrapper(r.originalOut, r.pwidth, r.currentIndent)
	return true
}

func (r *renderer) clearWrapper() {
	w, ok := r.out.(*wrapper)
	if !ok {
		return
	}

	if err := w.Flush(); err != nil {
		r.err = err
	}

	r.out = r.originalOut
}

func (r *renderer) renderInline(name string, rg renderGuide, a []Attributes, children []any) {
	newWrapper := r.ensureWrapper()
	printf := r.getPrintf(name)
	printf("<%s", name)
	r.renderAttributes(name, a)
	printf(">")
	if rg.void {
		if newWrapper {
			r.clearWrapper()
		}

		return
	}

	var lastBlock bool
	for _, c := range children {
		ct, isTag := c.(Tag)
		if !isTag && rg.verbatim {
			if c == nil {
				continue
			}

			s := fmt.Sprint(c)
			if s == "" {
				continue
			}

			r.clearWrapper()
			s = indentLines(r.currentIndent+r.indent.Indent, s)
			printf("\n%s", s)
			lastBlock = true
			continue
		}

		if !isTag && rg.script {
			if c == nil {
				continue
			}

			s := fmt.Sprint(c)
			if s == "" {
				continue
			}

			r.clearWrapper()
			printf("\n%s", s)
			lastBlock = true
			continue
		}

		if !isTag {
			if c == nil {
				continue
			}

			s := fmt.Sprint(c)
			if s == "" {
				continue
			}

			if lastBlock {
				printf("\n%s", r.currentIndent)
			}

			if r.ensureWrapper() {
				newWrapper = true
			}

			if r.err == nil {
				ew := newEscapeWriter(r.out)
				ew.Write([]byte(s))
				ew.Flush()
				r.err = ew.err
			}

			lastBlock = false
			continue
		}

		var rgq renderGuidesQuery
		ct(&rgq)
		crg := mergeRenderingGuides(rgq.value)
		if crg.inline {
			if lastBlock {
				printf("\n%s", r.currentIndent)
			}

			if r.ensureWrapper() {
				newWrapper = true
			}

			ct(r)
			lastBlock = false
			continue
		}

		r.clearWrapper()
		cr := new(renderer)
		*cr = *r
		cr.currentIndent += cr.indent.Indent
		cr.pwidth -= len([]rune(cr.indent.Indent))
		if cr.pwidth < cr.indent.MinPWidth {
			cr.pwidth = cr.indent.MinPWidth
		}

		printf("\n%s", cr.currentIndent)
		ct(cr)
		if cr.err != nil {
			r.err = cr.err
		}

		lastBlock = true
	}

	if lastBlock {
		printf("\n%s", r.currentIndent)
	}

	printf("</%s>", name)
	if newWrapper {
		r.clearWrapper()
	}
}

func (r *renderer) renderBlock(name string, rg renderGuide, a []Attributes, children []any) {
	printf := r.getPrintf(name)
	printf("<%s", name)
	r.renderAttributes(name, a)
	printf(">")
	if rg.void {
		return
	}

	if len(children) == 0 {
		printf("</%s>", name)
		return
	}

	lastBlock := true
	originalIndent, originalWidth := r.currentIndent, r.pwidth
	r.currentIndent += r.indent.Indent
	r.pwidth -= len([]rune(r.indent.Indent))
	if r.pwidth < r.indent.MinPWidth {
		r.pwidth = r.indent.MinPWidth
	}

	for _, c := range children {
		ct, isTag := c.(Tag)
		if !isTag && rg.verbatim {
			if c == nil {
				continue
			}

			s := fmt.Sprint(c)
			if s == "" {
				continue
			}

			r.clearWrapper()
			s = indentLines(r.currentIndent, s)
			printf("\n%s", s)
			lastBlock = true
			continue
		}

		if !isTag && rg.script {
			if c == nil {
				continue
			}

			s := fmt.Sprint(c)
			if s == "" {
				continue
			}

			r.clearWrapper()
			printf("\n%s", s)
			lastBlock = true
			continue
		}

		if !isTag {
			if c == nil {
				continue
			}

			s := fmt.Sprint(c)
			if s == "" {
				continue
			}

			if lastBlock {
				printf("\n%s", r.currentIndent)
			}

			r.ensureWrapper()
			if r.err == nil {
				ew := newEscapeWriter(r.out)
				ew.Write([]byte(s))
				ew.Flush()
				r.err = ew.err
			}

			lastBlock = false
			continue
		}

		var rgq renderGuidesQuery
		ct(&rgq)
		crg := mergeRenderingGuides(rgq.value)
		if crg.inline {
			if lastBlock {
				printf("\n%s", r.currentIndent)
			}

			r.ensureWrapper()
			ct(r)
			lastBlock = false
			continue
		}

		r.clearWrapper()
		cr := new(renderer)
		*cr = *r
		printf("\n%s", cr.currentIndent)
		ct(cr)
		if cr.err != nil {
			r.err = cr.err
		}

		lastBlock = true
	}

	r.clearWrapper()
	r.currentIndent, r.pwidth = originalIndent, originalWidth
	printf("\n%s</%s>", r.currentIndent, name)
}

func (r *renderer) render(name string, children []any) {
	if r.err != nil {
		return
	}

	a, c, rgs := groupChildren(children)
	rg := mergeRenderingGuides(rgs)
	if r.indent.Indent == "" && r.indent.PWidth <= 0 {
		r.renderUnindented(name, rg, a, c)
		return
	}

	if rg.inline || rg.inlineChildren {
		r.renderInline(name, rg, a, c)
		return
	}

	r.renderBlock(name, rg, a, c)
}