1 files changed, 287 insertions, 0 deletions
diff --git a/modules/templates/htmlrenderer.go b/modules/templates/htmlrenderer.go
new file mode 100644
index 00000000..55a55dd7
--- /dev/null
+++ b/modules/templates/htmlrenderer.go
@@ -0,0 +1,287 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package templates
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	texttemplate "text/template"
+
+	"code.gitea.io/gitea/modules/assetfs"
+	"code.gitea.io/gitea/modules/graceful"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/templates/scopedtmpl"
+	"code.gitea.io/gitea/modules/util"
+)
+
+type TemplateExecutor scopedtmpl.TemplateExecutor
+
+type HTMLRender struct {
+	templates atomic.Pointer[scopedtmpl.ScopedTemplate]
+}
+
+var (
+	htmlRender     *HTMLRender
+	htmlRenderOnce sync.Once
+)
+
+var ErrTemplateNotInitialized = errors.New("template system is not initialized, check your log for errors")
+
+func (h *HTMLRender) HTML(w io.Writer, status int, name string, data any, ctx context.Context) error { //nolint:revive
+	if respWriter, ok := w.(http.ResponseWriter); ok {
+		if respWriter.Header().Get("Content-Type") == "" {
+			respWriter.Header().Set("Content-Type", "text/html; charset=utf-8")
+		}
+		respWriter.WriteHeader(status)
+	}
+	t, err := h.TemplateLookup(name, ctx)
+	if err != nil {
+		return texttemplate.ExecError{Name: name, Err: err}
+	}
+	return t.Execute(w, data)
+}
+
+func (h *HTMLRender) TemplateLookup(name string, ctx context.Context) (TemplateExecutor, error) { //nolint:revive
+	tmpls := h.templates.Load()
+	if tmpls == nil {
+		return nil, ErrTemplateNotInitialized
+	}
+	m := NewFuncMap()
+	m["ctx"] = func() any { return ctx }
+	return tmpls.Executor(name, m)
+}
+
+func (h *HTMLRender) CompileTemplates() error {
+	assets := AssetFS()
+	extSuffix := ".tmpl"
+	tmpls := scopedtmpl.NewScopedTemplate()
+	tmpls.Funcs(NewFuncMap())
+	files, err := ListWebTemplateAssetNames(assets)
+	if err != nil {
+		return nil
+	}
+	for _, file := range files {
+		if !strings.HasSuffix(file, extSuffix) {
+			continue
+		}
+		name := strings.TrimSuffix(file, extSuffix)
+		tmpl := tmpls.New(filepath.ToSlash(name))
+		buf, err := assets.ReadFile(file)
+		if err != nil {
+			return err
+		}
+		if _, err = tmpl.Parse(string(buf)); err != nil {
+			return err
+		}
+	}
+	tmpls.Freeze()
+	h.templates.Store(tmpls)
+	return nil
+}
+
+// HTMLRenderer init once and returns the globally shared html renderer
+func HTMLRenderer() *HTMLRender {
+	htmlRenderOnce.Do(initHTMLRenderer)
+	return htmlRender
+}
+
+func ReloadHTMLTemplates() error {
+	log.Trace("Reloading HTML templates")
+	if err := htmlRender.CompileTemplates(); err != nil {
+		log.Error("Template error: %v\n%s", err, log.Stack(2))
+		return err
+	}
+	return nil
+}
+
+func initHTMLRenderer() {
+	rendererType := "static"
+	if !setting.IsProd {
+		rendererType = "auto-reloading"
+	}
+	log.Debug("Creating %s HTML Renderer", rendererType)
+
+	htmlRender = &HTMLRender{}
+	if err := htmlRender.CompileTemplates(); err != nil {
+		p := &templateErrorPrettier{assets: AssetFS()}
+		wrapTmplErrMsg(p.handleFuncNotDefinedError(err))
+		wrapTmplErrMsg(p.handleUnexpectedOperandError(err))
+		wrapTmplErrMsg(p.handleExpectedEndError(err))
+		wrapTmplErrMsg(p.handleGenericTemplateError(err))
+		wrapTmplErrMsg(fmt.Sprintf("CompileTemplates error: %v", err))
+	}
+
+	if !setting.IsProd {
+		go AssetFS().WatchLocalChanges(graceful.GetManager().ShutdownContext(), func() {
+			_ = ReloadHTMLTemplates()
+		})
+	}
+}
+
+func wrapTmplErrMsg(msg string) {
+	if msg == "" {
+		return
+	}
+	if setting.IsProd {
+		// in prod mode, Forgejo must have correct templates to run
+		log.Fatal("Forgejo can't run with template errors: %s", msg)
+	}
+	// in dev mode, do not need to really exit, because the template errors could be fixed by developer soon and the templates get reloaded
+	log.Error("There are template errors but Forgejo continues to run in dev mode: %s", msg)
+}
+
+type templateErrorPrettier struct {
+	assets *assetfs.LayeredFS
+}
+
+var reGenericTemplateError = regexp.MustCompile(`^template: (.*):([0-9]+): (.*)`)
+
+func (p *templateErrorPrettier) handleGenericTemplateError(err error) string {
+	groups := reGenericTemplateError.FindStringSubmatch(err.Error())
+	if len(groups) != 4 {
+		return ""
+	}
+	tmplName, lineStr, message := groups[1], groups[2], groups[3]
+	return p.makeDetailedError(message, tmplName, lineStr, -1, "")
+}
+
+var reFuncNotDefinedError = regexp.MustCompile(`^template: (.*):([0-9]+): (function "(.*)" not defined)`)
+
+func (p *templateErrorPrettier) handleFuncNotDefinedError(err error) string {
+	groups := reFuncNotDefinedError.FindStringSubmatch(err.Error())
+	if len(groups) != 5 {
+		return ""
+	}
+	tmplName, lineStr, message, funcName := groups[1], groups[2], groups[3], groups[4]
+	funcName, _ = strconv.Unquote(`"` + funcName + `"`)
+	return p.makeDetailedError(message, tmplName, lineStr, -1, funcName)
+}
+
+var reUnexpectedOperandError = regexp.MustCompile(`^template: (.*):([0-9]+): (unexpected "(.*)" in operand)`)
+
+func (p *templateErrorPrettier) handleUnexpectedOperandError(err error) string {
+	groups := reUnexpectedOperandError.FindStringSubmatch(err.Error())
+	if len(groups) != 5 {
+		return ""
+	}
+	tmplName, lineStr, message, unexpected := groups[1], groups[2], groups[3], groups[4]
+	unexpected, _ = strconv.Unquote(`"` + unexpected + `"`)
+	return p.makeDetailedError(message, tmplName, lineStr, -1, unexpected)
+}
+
+var reExpectedEndError = regexp.MustCompile(`^template: (.*):([0-9]+): (expected end; found (.*))`)
+
+func (p *templateErrorPrettier) handleExpectedEndError(err error) string {
+	groups := reExpectedEndError.FindStringSubmatch(err.Error())
+	if len(groups) != 5 {
+		return ""
+	}
+	tmplName, lineStr, message, unexpected := groups[1], groups[2], groups[3], groups[4]
+	return p.makeDetailedError(message, tmplName, lineStr, -1, unexpected)
+}
+
+var (
+	reTemplateExecutingError    = regexp.MustCompile(`^template: (.*):([1-9][0-9]*):([1-9][0-9]*): (executing .*)`)
+	reTemplateExecutingErrorMsg = regexp.MustCompile(`^executing "(.*)" at <(.*)>: `)
+)
+
+func (p *templateErrorPrettier) handleTemplateRenderingError(err error) string {
+	if groups := reTemplateExecutingError.FindStringSubmatch(err.Error()); len(groups) > 0 {
+		tmplName, lineStr, posStr, msgPart := groups[1], groups[2], groups[3], groups[4]
+		target := ""
+		if groups = reTemplateExecutingErrorMsg.FindStringSubmatch(msgPart); len(groups) > 0 {
+			target = groups[2]
+		}
+		return p.makeDetailedError(msgPart, tmplName, lineStr, posStr, target)
+	} else if execErr, ok := err.(texttemplate.ExecError); ok {
+		layerName := p.assets.GetFileLayerName(execErr.Name + ".tmpl")
+		return fmt.Sprintf("asset from: %s, %s", layerName, err.Error())
+	}
+	return err.Error()
+}
+
+func HandleTemplateRenderingError(err error) string {
+	p := &templateErrorPrettier{assets: AssetFS()}
+	return p.handleTemplateRenderingError(err)
+}
+
+const dashSeparator = "----------------------------------------------------------------------"
+
+func (p *templateErrorPrettier) makeDetailedError(errMsg, tmplName string, lineNum, posNum any, target string) string {
+	code, layer, err := p.assets.ReadLayeredFile(tmplName + ".tmpl")
+	if err != nil {
+		return fmt.Sprintf("template error: %s, and unable to find template file %q", errMsg, tmplName)
+	}
+	line, err := util.ToInt64(lineNum)
+	if err != nil {
+		return fmt.Sprintf("template error: %s, unable to parse template %q line number %q", errMsg, tmplName, lineNum)
+	}
+	pos, err := util.ToInt64(posNum)
+	if err != nil {
+		return fmt.Sprintf("template error: %s, unable to parse template %q pos number %q", errMsg, tmplName, posNum)
+	}
+	detail := extractErrorLine(code, int(line), int(pos), target)
+
+	var msg string
+	if pos >= 0 {
+		msg = fmt.Sprintf("template error: %s:%s:%d:%d : %s", layer, tmplName, line, pos, errMsg)
+	} else {
+		msg = fmt.Sprintf("template error: %s:%s:%d : %s", layer, tmplName, line, errMsg)
+	}
+	return msg + "\n" + dashSeparator + "\n" + detail + "\n" + dashSeparator
+}
+
+func extractErrorLine(code []byte, lineNum, posNum int, target string) string {
+	b := bufio.NewReader(bytes.NewReader(code))
+	var line []byte
+	var err error
+	for i := 0; i < lineNum; i++ {
+		if line, err = b.ReadBytes('\n'); err != nil {
+			if i == lineNum-1 && errors.Is(err, io.EOF) {
+				err = nil
+			}
+			break
+		}
+	}
+	if err != nil {
+		return fmt.Sprintf("unable to find target line %d", lineNum)
+	}
+
+	line = bytes.TrimRight(line, "\r\n")
+	var indicatorLine []byte
+	targetBytes := []byte(target)
+	targetLen := len(targetBytes)
+	for i := 0; i < len(line); {
+		if posNum == -1 && target != "" && bytes.HasPrefix(line[i:], targetBytes) {
+			for j := 0; j < targetLen && i < len(line); j++ {
+				indicatorLine = append(indicatorLine, '^')
+				i++
+			}
+		} else if i == posNum {
+			indicatorLine = append(indicatorLine, '^')
+			i++
+		} else {
+			if line[i] == '\t' {
+				indicatorLine = append(indicatorLine, '\t')
+			} else {
+				indicatorLine = append(indicatorLine, ' ')
+			}
+			i++
+		}
+	}
+	// if the indicatorLine only contains spaces, trim it together
+	return strings.TrimRight(string(line)+"\n"+string(indicatorLine), " \t\r\n")
+}