all: implement /s and /x redirector

Fixes #1
Fixes #2

Author: changkun

.gitignore

@@ -10,6 +10,8 @@
 
 # Output of the go coverage tool, specifically when used with LiteIDE
 *.out
+*.app
+*.rdb
 
 # Dependency directories (remove the comment below to include it)
-# vendor/
+vendor/

Makefile

@@ -0,0 +1,29 @@
+# Copyright 2020 The golang.design Initiative authors.
+# All rights reserved. Use of this source code is governed
+# by a MIT license that can be found in the LICENSE file.
+
+VERSION = $(shell git describe --always --tags)
+BUILDTIME = $(shell date +%FT%T%z)
+GOPATH=$(shell go env GOPATH)
+IMAGE = golang-design/redir
+BINARY = redir.app
+TARGET = -o $(BINARY)
+BUILD_SETTINGS = -ldflags="-X main.Version=$(VERSION) -X main.BuildTime=$(BUILDTIME)"
+BUILD_FLAGS = $(TARGET) $(BUILD_SETTINGS)
+
+all: native
+native:
+	GO111MODULE=on go build $(BUILD_FLAGS)
+run:
+	./$(BINARY) -s
+build:
+	docker build -t $(IMAGE):$(VERSION) -t $(IMAGE):latest -f docker/Dockerfile .
+compose:
+	docker-compose -f docker/docker-compose.yml up -d
+compose-down:
+	docker-compose -f docker/docker-compose.yml down
+clean:
+	rm redir.app
+	docker rmi -f $(shell docker images -f "dangling=true" -q) 2> /dev/null; true
+	docker rmi -f $(IMAGE):latest $(IMAGE):$(VERSION) 2> /dev/null; true
+.PHONY: native run build compose clean

README.md

@@ -1,2 +1,82 @@
 # redir
+
 a request redirector that is dedicated for golang.design
+
+## Design Purpose
+
+The current `redir` implementation talks to a redis data store for PV/UV counting,
+as well as short alias storage. In the booting phase, it will read `REDIR_CONF`
+from environment variable to identify configuration file (default: `./config.yml`).
+
+`redir` is designed for the following purpose: serve two major
+redirectors `/s` and `/x` (at the moment).
+
+### 1. Redirect `golang.design/x/pkg` to the `pkg`'s actual VCS.
+
+This is based on the `go get` vanity import path convention. With this
+feature, all packages issued by [golang.design](https://golang.design) 
+requires to use `golang.design/x/` import path.
+That is saying, any `pkg` will be redirected to `github.com/golang-design/pkg`
+if exist. The website itself will redirect the request to [pkg.go.dev](https://pkg.go.dev).
+
+There is a reserved ping router for debugging purpose `/x/.ping` which will
+give you a pong.
+
+### 2. Redirect `golang.design/s/alias`
+
+The served alias can be allocated by [golang.design](https://golang.design/) members.
+The current approach is to use `redir` command on the [golang.design](https://golang.design/)
+server. Here is the overview of its usage:
+
+```
+usage: redir [-s] [-op <operator> -a <alias> -l <link>]
+options:
+  -a string
+        alias for a new link
+  -l string
+        actual link for the alias, optional for delete/fetch
+  -op string
+        operators, create/update/delete/fetch (default "create")
+  -s    run redir service
+example:
+redir -s                  run the redir service
+redir -a alias -l link    allocate new short link if possible
+redir -op fetch -a alias  fetch alias information
+```
+
+For the command line usage, one only need to use `-a`, `-l` and `-op` if needed.
+The command will talk to the redis data store and issue a new allocated alias.
+For instance, the following command:
+
+```
+redir -a changkun -l https://changkun.de
+```
+
+creates a new alias under [golang.design/s/changkun](https://golang.design/s/changkun).
+
+Moreover, it is possible to visit [`/s`](https://golang.design/s) directly listing all exist aliases under [golang.design](https://golang.design/).
+
+## Build
+
+`Makefile` defines different ways to build the service:
+
+```bash
+make              # build native binary
+make run          # assume your local redis is running
+make build        # build docker images
+make compose      # run via docker-compose
+make compose-down # remove compose stuff
+make clean        # cleanup
+```
+
+## Troubleshooting
+
+### private golang.design projects `go get` failure
+
+1. make sure you are a member of golang.design
+2. add ssh public key to your account
+3. `git config --global url."[email protected]:".insteadOf "https://github.com/"`
+
+## License
+
+MIT &copy; The golang.design Initiative Authors

config.go

@@ -0,0 +1,59 @@
+// Copyright 2020 The golang.design Initiative authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"runtime"
+
+	"gopkg.in/yaml.v2"
+)
+
+// build info, assign by compile time or runtime.
+var (
+	Version   string
+	BuildTime string
+	GoVersion = runtime.Version()
+)
+
+type config struct {
+	Host  string `json:"host"`
+	Addr  string `json:"addr"`
+	Store string `json:"store"`
+	Log   string `json:"log"`
+	S     struct {
+		Prefix string `json:"prefix"`
+	} `json:"s"`
+	X struct {
+		Prefix     string `json:"prefix"`
+		VCS        string `json:"vcs"`
+		ImportPath string `json:"import_path"`
+		RepoPath   string `json:"repo_path"`
+	} `json:"x"`
+}
+
+func (c *config) parse() {
+	f := os.Getenv("REDIR_CONF")
+	d, err := ioutil.ReadFile(f)
+	if err != nil {
+		// Just try again with default setting.
+		d, err = ioutil.ReadFile("./config.yml")
+		if err != nil {
+			log.Fatalf("cannot read configuration, err: %v\n", err)
+		}
+	}
+	err = yaml.Unmarshal(d, c)
+	if err != nil {
+		log.Fatalf("cannot parse configuration, err: %v\n", err)
+	}
+}
+
+var conf config
+
+func init() {
+	conf.parse()
+}

config.yml

@@ -0,0 +1,16 @@
+# Copyright 2020 The golang.design Initiative authors.
+# All rights reserved. Use of this source code is governed
+# by a MIT license that can be found in the LICENSE file.
+
+---
+host: https://golang.design
+addr: :8080
+store: redis://localhost:6379/9
+log: "golang.design/redir: "
+s:
+  prefix: /s/
+x:
+  prefix: /x/
+  vcs: git
+  import_path: golang.design/x/*
+  repo_path: https://github.com/golang-design/*

config_test.go

@@ -0,0 +1,27 @@
+// Copyright 2020 The golang.design Initiative authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestParseConfig(t *testing.T) {
+	conf.parse()
+
+	// Test if all fields are filled.
+	v := reflect.ValueOf(conf)
+	for i := 0; i < v.NumField(); i++ {
+		if v.Field(i).Kind() == reflect.Struct {
+			continue
+		}
+		vv, ok := v.Field(i).Interface().(string)
+		if ok && len(vv) > 0 {
+			continue
+		}
+		t.Fatalf("read empty from config, field: %v", v.Type().Field(i).Name)
+	}
+}

data/container.yml

@@ -0,0 +1,16 @@
+# Copyright 2020 The golang.design Initiative authors.
+# All rights reserved. Use of this source code is governed
+# by a MIT license that can be found in the LICENSE file.
+
+---
+host: https://golang.design/
+addr: :8080
+store: redis://redis:6379/9
+log: "golang.design/redir: "
+s:
+  prefix: /s/
+x:
+  prefix: /x/
+  vcs: git
+  import_path: golang.design/x/*
+  repo_path: https://github.com/golang-design/*