// Copyright 2023 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package templates

import (
	"context"
	"encoding/hex"
	"fmt"
	"html/template"
	"math"
	"net/url"
	"regexp"
	"strings"
	"unicode"

	issues_model "code.gitea.io/gitea/models/issues"
	"code.gitea.io/gitea/modules/emoji"
	"code.gitea.io/gitea/modules/htmlutil"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/markup"
	"code.gitea.io/gitea/modules/markup/markdown"
	"code.gitea.io/gitea/modules/setting"
	"code.gitea.io/gitea/modules/translation"
	"code.gitea.io/gitea/modules/util"
)

type RenderUtils struct {
	ctx context.Context
}

func NewRenderUtils(ctx context.Context) *RenderUtils {
	return &RenderUtils{ctx: ctx}
}

// RenderCommitMessage renders commit message with XSS-safe and special links.
func (ut *RenderUtils) RenderCommitMessage(msg string, metas map[string]string) template.HTML {
	cleanMsg := template.HTMLEscapeString(msg)
	// we can safely assume that it will not return any error, since there
	// shouldn't be any special HTML.
	fullMessage, err := markup.RenderCommitMessage(markup.NewRenderContext(ut.ctx).WithMetas(metas), cleanMsg)
	if err != nil {
		log.Error("RenderCommitMessage: %v", err)
		return ""
	}
	msgLines := strings.Split(strings.TrimSpace(fullMessage), "\n")
	if len(msgLines) == 0 {
		return template.HTML("")
	}
	return renderCodeBlock(template.HTML(msgLines[0]))
}

// RenderCommitMessageLinkSubject renders commit message as a XSS-safe link to
// the provided default url, handling for special links without email to links.
func (ut *RenderUtils) RenderCommitMessageLinkSubject(msg, urlDefault string, metas map[string]string) template.HTML {
	msgLine := strings.TrimLeftFunc(msg, unicode.IsSpace)
	lineEnd := strings.IndexByte(msgLine, '\n')
	if lineEnd > 0 {
		msgLine = msgLine[:lineEnd]
	}
	msgLine = strings.TrimRightFunc(msgLine, unicode.IsSpace)
	if len(msgLine) == 0 {
		return ""
	}

	// we can safely assume that it will not return any error, since there
	// shouldn't be any special HTML.
	renderedMessage, err := markup.RenderCommitMessageSubject(markup.NewRenderContext(ut.ctx).WithMetas(metas), urlDefault, template.HTMLEscapeString(msgLine))
	if err != nil {
		log.Error("RenderCommitMessageSubject: %v", err)
		return ""
	}
	return renderCodeBlock(template.HTML(renderedMessage))
}

// RenderCommitBody extracts the body of a commit message without its title.
func (ut *RenderUtils) RenderCommitBody(msg string, metas map[string]string) template.HTML {
	msgLine := strings.TrimSpace(msg)
	lineEnd := strings.IndexByte(msgLine, '\n')
	if lineEnd > 0 {
		msgLine = msgLine[lineEnd+1:]
	} else {
		return ""
	}
	msgLine = strings.TrimLeftFunc(msgLine, unicode.IsSpace)
	if len(msgLine) == 0 {
		return ""
	}

	renderedMessage, err := markup.RenderCommitMessage(markup.NewRenderContext(ut.ctx).WithMetas(metas), template.HTMLEscapeString(msgLine))
	if err != nil {
		log.Error("RenderCommitMessage: %v", err)
		return ""
	}
	return template.HTML(renderedMessage)
}

// Match text that is between back ticks.
var codeMatcher = regexp.MustCompile("`([^`]+)`")

// renderCodeBlock renders "`…`" as highlighted "<code>" block, intended for issue and PR titles
func renderCodeBlock(htmlEscapedTextToRender template.HTML) template.HTML {
	htmlWithCodeTags := codeMatcher.ReplaceAllString(string(htmlEscapedTextToRender), `<code class="inline-code-block">$1</code>`) // replace with HTML <code> tags
	return template.HTML(htmlWithCodeTags)
}

// RenderIssueTitle renders issue/pull title with defined post processors
func (ut *RenderUtils) RenderIssueTitle(text string, metas map[string]string) template.HTML {
	renderedText, err := markup.RenderIssueTitle(markup.NewRenderContext(ut.ctx).WithMetas(metas), template.HTMLEscapeString(text))
	if err != nil {
		log.Error("RenderIssueTitle: %v", err)
		return ""
	}
	return template.HTML(renderedText)
}

// RenderLabel renders a label
func (ut *RenderUtils) RenderLabel(label *issues_model.Label) template.HTML {
	locale := ut.ctx.Value(translation.ContextKey).(translation.Locale)
	var extraCSSClasses string
	textColor := util.ContrastColor(label.Color)
	labelScope := label.ExclusiveScope()
	descriptionText := emoji.ReplaceAliases(label.Description)

	if label.IsArchived() {
		extraCSSClasses = "archived-label"
		descriptionText = fmt.Sprintf("(%s) %s", locale.TrString("archived"), descriptionText)
	}

	if labelScope == "" {
		// Regular label
		return htmlutil.HTMLFormat(`<div class="ui label %s" style="color: %s !important; background-color: %s !important;" data-tooltip-content title="%s">%s</div>`,
			extraCSSClasses, textColor, label.Color, descriptionText, ut.RenderEmoji(label.Name))
	}

	// Scoped label
	scopeHTML := ut.RenderEmoji(labelScope)
	itemHTML := ut.RenderEmoji(label.Name[len(labelScope)+1:])

	// Make scope and item background colors slightly darker and lighter respectively.
	// More contrast needed with higher luminance, empirically tweaked.
	luminance := util.GetRelativeLuminance(label.Color)
	contrast := 0.01 + luminance*0.03
	// Ensure we add the same amount of contrast also near 0 and 1.
	darken := contrast + math.Max(luminance+contrast-1.0, 0.0)
	lighten := contrast + math.Max(contrast-luminance, 0.0)
	// Compute factor to keep RGB values proportional.
	darkenFactor := math.Max(luminance-darken, 0.0) / math.Max(luminance, 1.0/255.0)
	lightenFactor := math.Min(luminance+lighten, 1.0) / math.Max(luminance, 1.0/255.0)

	r, g, b := util.HexToRBGColor(label.Color)
	scopeBytes := []byte{
		uint8(math.Min(math.Round(r*darkenFactor), 255)),
		uint8(math.Min(math.Round(g*darkenFactor), 255)),
		uint8(math.Min(math.Round(b*darkenFactor), 255)),
	}
	itemBytes := []byte{
		uint8(math.Min(math.Round(r*lightenFactor), 255)),
		uint8(math.Min(math.Round(g*lightenFactor), 255)),
		uint8(math.Min(math.Round(b*lightenFactor), 255)),
	}

	itemColor := "#" + hex.EncodeToString(itemBytes)
	scopeColor := "#" + hex.EncodeToString(scopeBytes)

	return htmlutil.HTMLFormat(`<span class="ui label %s scope-parent" data-tooltip-content title="%s">`+
		`<div class="ui label scope-left" style="color: %s !important; background-color: %s !important">%s</div>`+
		`<div class="ui label scope-right" style="color: %s !important; background-color: %s !important">%s</div>`+
		`</span>`,
		extraCSSClasses, descriptionText,
		textColor, scopeColor, scopeHTML,
		textColor, itemColor, itemHTML)
}

// RenderEmoji renders html text with emoji post processors
func (ut *RenderUtils) RenderEmoji(text string) template.HTML {
	renderedText, err := markup.RenderEmoji(markup.NewRenderContext(ut.ctx), template.HTMLEscapeString(text))
	if err != nil {
		log.Error("RenderEmoji: %v", err)
		return ""
	}
	return template.HTML(renderedText)
}

// reactionToEmoji renders emoji for use in reactions
func reactionToEmoji(reaction string) template.HTML {
	val := emoji.FromCode(reaction)
	if val != nil {
		return template.HTML(val.Emoji)
	}
	val = emoji.FromAlias(reaction)
	if val != nil {
		return template.HTML(val.Emoji)
	}
	return template.HTML(fmt.Sprintf(`<img alt=":%s:" src="%s/assets/img/emoji/%s.png"></img>`, reaction, setting.StaticURLPrefix, url.PathEscape(reaction)))
}

func (ut *RenderUtils) MarkdownToHtml(input string) template.HTML { //nolint:revive
	output, err := markdown.RenderString(markup.NewRenderContext(ut.ctx).WithMetas(markup.ComposeSimpleDocumentMetas()), input)
	if err != nil {
		log.Error("RenderString: %v", err)
	}
	return output
}

func (ut *RenderUtils) RenderLabels(labels []*issues_model.Label, repoLink string, issue *issues_model.Issue) template.HTML {
	isPullRequest := issue != nil && issue.IsPull
	baseLink := fmt.Sprintf("%s/%s", repoLink, util.Iif(isPullRequest, "pulls", "issues"))
	htmlCode := `<span class="labels-list">`
	for _, label := range labels {
		// Protect against nil value in labels - shouldn't happen but would cause a panic if so
		if label == nil {
			continue
		}
		htmlCode += fmt.Sprintf(`<a href="%s?labels=%d">%s</a>`, baseLink, label.ID, ut.RenderLabel(label))
	}
	htmlCode += "</span>"
	return template.HTML(htmlCode)
}