feat(server): apis, test, readme, ui, storage, metrics

Author: paologallinaharbur

.gitignore

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+my.db

.idea/.gitignore

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+
+URL shortener
+-
+This is an example of how to create a URL shortener using:
+
+ - go-swagger as api Framework (OpenAPI 2.0)
+ - swagger-ui as frontend to publish documentation and provide a way to test APIs
+ - The apis logic need storage, that is passed as an `interface` to make easier change it
+ 	"github.com/boltdb/bolt" has been chosen as implementation since it is a quick key-value db
+ - prometheus is used to expose metrics under /metrics.
+ - dependencies are managed through `go mod`
+ - redirection is performed before hitting the API in the middleware
+ - error management is present but covers only most common cases
+ 
+The code NOT autogenerated is:
+   
+   - `storage` package (logic of storage)
+   - `middlewares` package (logic to redirect, prometheus)
+   - `url_implementation` package (logic of APIs)
+   - `restapi/operation/configure_url_shortener.go` file (linking pieces)
+   - `swagger-ui/swagger.yml` file (open-api definition, used to auto-generate the code)
+
+The code autogenerated is NOT covered by tests, everything else has a coverage of ~ 80%
+
+![image](./UI.png)
+
+
+Development:
+-
+
+To add new Api modify `swagger-ui/swagger.yml` and run:
+ 
+ `$swagger generate server  -f ./swagger-ui/swagger.yml --exclude-main`
+
+Be aware, if you modify any autogenerated file it will be overwritten running such command.
+
+Run test running:
+  `$go test ./...`
+
+Usage
+-
+To execute the server clone the repo, cd into it and run:
+
+`$go run ./cmd/url-shortener-server/main.go --port 35307`
+
+Navigate to `localhost:35307/swagger-ui` to visualise the UI and test APIs with a frontend
+Navigate to `localhost:35307/metrics` to check metrics, in particular `url_redirected` keeps track of redirection since last execution
+
+There are three methods under `/api`:
+ - POST `/api` that accept in the json body the URL to make shorter
+ - GET `/api/{shortURL}` that returns the URL corresponding to shortURL
+ - DELETE `/api/{shortURL}` that delete the URL
+
+Shortened URLs will be like `short-abcdefghil` and can be used as follows `localhost:35307/short-abcdefghil`
+
+If you try to navigate to a shortened url that does not exist (es: `localhost:35307/short-notExisting`) you will be redirected to `http://www.notfound.com`

.idea/misc.xml

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+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/go-openapi/loads"
+	flags "github.com/jessevdk/go-flags"
+	"github.com/paologallinaharbur/shorturl/restapi"
+	"github.com/paologallinaharbur/shorturl/restapi/operations"
+)
+
+func main() {
+
+	swaggerSpec, err := loads.Embedded(restapi.SwaggerJSON, restapi.FlatSwaggerJSON)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	api := operations.NewURLShortenerAPI(swaggerSpec)
+	server := restapi.NewServer(api)
+	defer server.Shutdown()
+
+	parser := flags.NewParser(server, flags.Default)
+	parser.ShortDescription = "url shortener"
+	parser.LongDescription = swaggerSpec.Spec().Info.Description
+	server.ConfigureFlags()
+	for _, optsGroup := range api.CommandLineOptionsGroups {
+		_, err := parser.AddGroup(optsGroup.ShortDescription, optsGroup.LongDescription, optsGroup.Options)
+		if err != nil {
+			log.Fatalln(err)
+		}
+	}
+
+	if _, err := parser.Parse(); err != nil {
+		code := 1
+		if fe, ok := err.(*flags.Error); ok {
+			if fe.Type == flags.ErrHelp {
+				code = 0
+			}
+		}
+		os.Exit(code)
+	}
+
+	server.ConfigureAPI()
+
+	if err := server.Serve(); err != nil {
+		log.Fatalln(err)
+	}
+
+}

.idea/modules.xml

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+module github.com/paologallinaharbur/shorturl
+
+go 1.14
+
+require (
+	github.com/boltdb/bolt v1.3.1
+	github.com/go-openapi/errors v0.19.6
+	github.com/go-openapi/loads v0.19.5
+	github.com/go-openapi/runtime v0.19.19
+	github.com/go-openapi/spec v0.19.8
+	github.com/go-openapi/strfmt v0.19.5
+	github.com/go-openapi/swag v0.19.9
+	github.com/go-openapi/validate v0.19.10
+	github.com/jessevdk/go-flags v1.4.0
+	github.com/prometheus/client_golang v1.7.1
+	github.com/stretchr/testify v1.6.1
+	golang.org/x/net v0.0.0-20200707034311-ab3426394381
+	golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae // indirect
+)