Init

LICENSE

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+MIT License
+
+Copyright (c) 2022 darkweak
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+go-esi
+------
+
+go-esi is the implementation of the non-standard ESI (Edge-Side-Include) specification from the w3. With that you'll be able to use the ESI tags and process them in your favorite golang servers.
+
+## References
+https://www.w3.org/TR/esi-lang/
+
+## Install
+```bash
+go get -u github.com/darkweak/go-esi
+```
+
+## Roadmap
+- [ ] choose tag
+- [x] comment tag
+- [ ] escape tag
+- [x] include tag
+- [x] remove tag
+- [ ] otherwise tag
+- [ ] try tag
+- [ ] vars tag
+- [ ] when tag

esi/errors.go

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+package esi
+
+import "errors"
+
+var errNotFound = errors.New("not found")

esi/esi.go

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+package esi
+
+import (
+	"net/http"
+)
+
+func findTagName(b []byte) tag {
+	name := tagname.FindSubmatch(b)
+	if name == nil {
+		return nil
+	}
+
+	switch string(name[1]) {
+	case comment:
+		return &commentTag{
+			baseTag: newBaseTag(),
+		}
+	case choose:
+	case escape:
+	case include:
+		return &includeTag{
+			baseTag: newBaseTag(),
+		}
+	case remove:
+		return &removeTag{
+			baseTag: newBaseTag(),
+		}
+	case otherwise:
+	case try:
+	case vars:
+	case when:
+	default:
+	}
+
+	return nil
+}
+
+func Parse(b []byte, req *http.Request) []byte {
+	pointer := 0
+
+	for pointer < len(b) {
+		next := b[pointer:]
+		tagIdx := esi.FindIndex(next)
+
+		if tagIdx == nil {
+			break
+		}
+
+		esiPointer := tagIdx[1]
+		t := findTagName(next[esiPointer:])
+
+		res, p := t.process(next[esiPointer:], req)
+		esiPointer += p
+
+		b = append(b[:pointer], append(next[:tagIdx[0]], append(res, next[esiPointer:]...)...)...)
+		pointer += len(res)
+	}
+
+	return b
+}

esi/esi_test.go

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+package esi
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+func loadFromFixtures(name string) []byte {
+	b, e := os.ReadFile("../fixtures/" + name)
+	if e != nil {
+		panic("The file " + name + " doesn't exist.")
+	}
+
+	return b
+}
+
+var (
+	commentMock = loadFromFixtures("comment")
+	// chooseMock  = loadFromFixtures("choose")
+	// escapeMock  = loadFromFixtures("escape")
+	includeMock = loadFromFixtures("include")
+	removeMock  = loadFromFixtures("remove")
+	// tryMock     = loadFromFixtures("try")
+	// varsMock    = loadFromFixtures("vars")
+)
+
+func Test_Parse_includeMock(t *testing.T) {
+	fmt.Println(string(commentMock))
+	fmt.Println(string(includeMock))
+	fmt.Println(string(removeMock))
+	// x := Parse(removeMock, httptest.NewRequest(http.MethodGet, "/", nil))
+	// t.Error(string(x))
+}

esi/tags.go

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+package esi
+
+import "regexp"
+
+const (
+	choose    = "choose"
+	comment   = "comment"
+	escape    = "escape"
+	include   = "include"
+	remove    = "remove"
+	otherwise = "otherwise"
+	try       = "try"
+	vars      = "vars"
+	when      = "when"
+)
+
+var (
+	esi     = regexp.MustCompile("<esi:")
+	tagname = regexp.MustCompile("^([a-z]+?)( |>)")
+
+	// closeChoose    = regexp.MustCompile("</esi:choose>")
+	closeComment = regexp.MustCompile("/>")
+	closeInclude = regexp.MustCompile("/>")
+	closeRemove  = regexp.MustCompile("</esi:remove>")
+	// closeOtherwise = regexp.MustCompile("</esi:otherwise>")
+	// closeTry       = regexp.MustCompile("</esi:try>")
+	// closeVars      = regexp.MustCompile("</esi:vars>")
+	// closeWhen      = regexp.MustCompile("</esi:when>")
+
+	srcAttribute = regexp.MustCompile(`src="?(.+?)"?( |/>)`)
+	altAttribute = regexp.MustCompile(`alt="?(.+?)"?( |/>)`)
+)

esi/type.go

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+package esi
+
+import (
+	"io"
+	"net/http"
+	"sync"
+)
+
+var clientPool = &sync.Pool{
+	New: func() any {
+		return &http.Client{}
+	},
+}
+
+type (
+	tag interface {
+		process([]byte, *http.Request) ([]byte, int)
+	}
+
+	baseTag struct {
+		length int
+	}
+	includeTag struct {
+		*baseTag
+		src string
+		alt string
+	}
+	removeTag struct {
+		*baseTag
+	}
+	commentTag struct {
+		*baseTag
+	}
+)
+
+func newBaseTag() *baseTag {
+	return &baseTag{}
+}
+
+func (b *baseTag) process(content []byte, _ *http.Request) ([]byte, int) {
+	return []byte{}, len(content)
+}
+
+func (i *includeTag) loadAttributes(b []byte) error {
+	src := srcAttribute.FindSubmatch(b)
+	if src == nil {
+		return errNotFound
+	}
+	i.src = string(src[1])
+
+	alt := altAttribute.FindSubmatch(b)
+	if alt != nil {
+		i.alt = string(alt[1])
+	}
+
+	return nil
+}
+
+// Input (e.g. include src="https://domain.com/esi-include" alt="https://domain.com/alt-esi-include" />)
+// With or without the alt
+// With or without a space separator before the closing
+// With or without the quotes around the src/alt value
+func (i *includeTag) process(b []byte, req *http.Request) ([]byte, int) {
+	closeIdx := closeInclude.FindIndex(b)
+
+	if closeIdx == nil {
+		return nil, len(b)
+	}
+
+	i.length = closeIdx[1]
+	if e := i.loadAttributes(b[8:i.length]); e != nil {
+		return nil, len(b)
+	}
+
+	rq, _ := http.NewRequest(http.MethodGet, i.src, nil)
+	response, err := clientPool.Get().(*http.Client).Do(rq)
+	if err != nil || response.StatusCode >= 400 {
+		rq, _ = http.NewRequest(http.MethodGet, i.src, nil)
+		response, err = clientPool.Get().(*http.Client).Do(rq)
+		if err != nil || response.StatusCode >= 400 {
+			return nil, len(b)
+		}
+	}
+
+	x, _ := io.ReadAll(response.Body)
+	b = Parse(x, req)
+
+	return b, i.length
+}
+
+// Input (e.g. comment text="This is a comment." />)
+func (c *commentTag) process(b []byte, req *http.Request) ([]byte, int) {
+	found := closeComment.FindIndex(b)
+	if found == nil {
+		return nil, len(b)
+	}
+	c.length = found[1]
+
+	return []byte{}, len(b)
+}
+
+func (r *removeTag) process(b []byte, req *http.Request) ([]byte, int) {
+	closeIdx := closeRemove.FindIndex(b)
+	if closeIdx == nil {
+		return []byte{}, len(b)
+	}
+	r.length = closeIdx[1]
+
+	return []byte{}, r.length
+}

fixtures/choose

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+<esi:choose> 
+    <esi:when test="$(HTTP_COOKIE{group})=='Advanced'"> 
+        <esi:include src="http://www.example.com/advanced.html"/> 
+    </esi:when> 
+    <esi:when test="$(HTTP_COOKIE{group})=='Basic User'">
+        <esi:include src="http://www.example.com/basic.html"/>
+    </esi:when> 
+    <esi:otherwise> 
+        <esi:include src="http://www.example.com/new_user.html"/> 
+    </esi:otherwise>
+</esi:choose>

fixtures/comment

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+<esi:comment text="the following animation will have a 24 hr TTL." />
+<esi:include src="http://domain.com/chained-esi-include-1" alt=http://domain.com/alt-esi-include/>

fixtures/escape

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+<!--esi  
+  <p><esi:vars>Hello, $(HTTP_COOKIE{name})!</esi:vars></p>
+-->

fixtures/include

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+<esi:include src="http://domain.com/chained-esi-include-1" alt=http://domain.com/alt-esi-include/>
+<h2>blah</h2>

fixtures/remove

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+<esi:include src="http://domain.com/chained-esi-include-1"/>
+<esi:remove>
+  <a href="http://www.example.com">www.example.com</a>
+</esi:remove>
+<esi:include src="http://domain.com/chained-esi-include-1"/>
+<esi:include src="http://domain.com/chained-esi-include-1"/>

fixtures/try

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+<esi:try> 
+    <esi:attempt>
+        <esi:comment text="Include an ad"/> 
+        <esi:include src="http://www.example.com/ad1.html"/> 
+    </esi:attempt>
+    <esi:except> 
+        <esi:comment text="Just write some HTML instead"/> 
+        <a href="www.akamai.com">www.example.com</a>
+    </esi:except> 
+</esi:try>

fixtures/vars

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+<esi:vars>
+  <img src="http://www.example.com/$(HTTP_COOKIE{type})/hello.gif"/ >
+</esi:vars>

go.mod

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+module github.com/darkweak/go-esi
+
+go 1.18

mock/Caddyfile

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+{
+    debug
+}
+
+:80 {
+    respond 404
+
+    route /chained-esi-include-1 {
+        header Content-Type text/html
+        respond `<esi:include src="http://domain.com/chained-esi-include-2"/>`
+    }
+
+    route /chained-esi-include-2 {
+        header Content-Type text/html
+        respond "<h1>CHAINED 2</h1>"
+    }
+
+    route /esi-include {
+        header Content-Type text/html
+        respond "<h1>ESI INCLUDE</h1>"
+    }
+
+    route /alt-esi-include {
+        header Content-Type text/html
+        respond "<h1>ALTERNATE ESI INCLUDE</h1>"
+    }
+}