Rewrite project, add daily update of services list

The project was rewritten from Elixir to Go, primarily because:

- I don't write Elixir anymore and don't want to maintain a project in a
  language I no longer write
- I already write Go for other projects, including my day job, so it's
  a safer bet for a project that I want to maintain long term
- Go allows me to build portable executables that will make it easier
  for others to run farside on their own machines

The Go version of Farsside also has a built in task to fetch the latest
services{-full}.json file from the repo and ingest it, which makes
running a farside server a lot simpler.

It also automatically fetches the latest instance state from
https://farside.link unless configured as a primary farside node, which
will allow others to use farside without increasing traffic to all
instances that are queried by farside (just to the farside node itself).

2 files changed, 203 insertions, 0 deletions

diff --git a/services/mappings.go b/services/mappings.go
new file mode 100644
index 0000000..53731a6
--- /dev/null
+++ b/services/mappings.go
@@ -0,0 +1,110 @@
+package services
+
+import (
+	"errors"
+	"math/rand"
+	"regexp"
+)
+
+type RegexMapping struct {
+	Pattern *regexp.Regexp
+	Targets []string
+}
+
+var regexMap = []RegexMapping{
+	{
+		// YouTube
+		Pattern: regexp.MustCompile(`youtu(\.be|be\.com)|invidious|piped`),
+		Targets: []string{"piped", "invidious"},
+	},
+	{
+		// Twitter / X
+		Pattern: regexp.MustCompile(`twitter\.com|x\.com|nitter`),
+		Targets: []string{"nitter"},
+	},
+	{
+		// Reddit
+		Pattern: regexp.MustCompile(`reddit\.com|libreddit|redlib`),
+		Targets: []string{"libreddit", "redlib"},
+	},
+	{
+		// Google Search
+		Pattern: regexp.MustCompile(`google\.com|whoogle|searx|searxng`),
+		Targets: []string{"whoogle", "searx", "searxng"},
+	},
+	{
+		// Instagram
+		Pattern: regexp.MustCompile(`instagram\.com|proxigram`),
+		Targets: []string{"proxigram"},
+	},
+	{
+		// Wikipedia
+		Pattern: regexp.MustCompile(`wikipedia\.org|wikiless`),
+		Targets: []string{"wikiless"},
+	},
+	{
+		// Medium
+		Pattern: regexp.MustCompile(`medium\.com|scribe`),
+		Targets: []string{"scribe"},
+	},
+	{
+		// Odysee
+		Pattern: regexp.MustCompile(`odysee\.com|librarian`),
+		Targets: []string{"librarian"},
+	},
+	{
+		// Imgur
+		Pattern: regexp.MustCompile(`imgur\.com|rimgo`),
+		Targets: []string{"rimgo"},
+	},
+	{
+		// Google Translate
+		Pattern: regexp.MustCompile(`translate\.google\.com|lingva`),
+		Targets: []string{"lingva"},
+	},
+	{
+		// TikTok
+		Pattern: regexp.MustCompile(`tiktok\.com|proxitok`),
+		Targets: []string{"proxitok"},
+	},
+	{
+		// Fandom
+		Pattern: regexp.MustCompile(`fandom\.com|breezewiki`),
+		Targets: []string{"breezewiki"},
+	},
+	{
+		// IMDB
+		Pattern: regexp.MustCompile(`imdb\.com|libremdb`),
+		Targets: []string{"libremdb"},
+	},
+	{
+		// Quora
+		Pattern: regexp.MustCompile(`quora\.com|quetre`),
+		Targets: []string{"quetre"},
+	},
+	{
+		// GitHub
+		Pattern: regexp.MustCompile(`github\.com|gothub`),
+		Targets: []string{"gothub"},
+	},
+	{
+		// StackOverflow
+		Pattern: regexp.MustCompile(`stackoverflow\.com|anonymousoverflow`),
+		Targets: []string{"anonymousoverflow"},
+	},
+}
+
+func MatchRequest(service string) (string, error) {
+	for _, mapping := range regexMap {
+		hasMatch := mapping.Pattern.MatchString(service)
+		if !hasMatch {
+			continue
+		}
+
+		index := rand.Intn(len(mapping.Targets))
+		value := mapping.Targets[index]
+		return value, nil
+	}
+
+	return "", errors.New("no match found")
+}
diff --git a/services/services.go b/services/services.go
new file mode 100644
index 0000000..b9e5693
--- /dev/null
+++ b/services/services.go
@@ -0,0 +1,93 @@
+package services
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"os"
+)
+
+var (
+	ServiceList []Service
+	FallbackMap map[string]string
+)
+
+const (
+	baseRepoLink = "https://git.sr.ht/~benbusby/farside/blob/main/"
+
+	noCFServicesJSON = "services.json"
+	fullServicesJSON = "services-full.json"
+)
+
+type Service struct {
+	Type      string   `json:"type"`
+	TestURL   string   `json:"test_url,omitempty"`
+	Fallback  string   `json:"fallback,omimtempty"`
+	Instances []string `json:"instances"`
+}
+
+func ingestServicesList(servicesBytes []byte) error {
+	err := json.Unmarshal(servicesBytes, &ServiceList)
+	return err
+}
+
+func GetServicesFileName() string {
+	cloudflareEnabled := false
+
+	cfEnabledVar := os.Getenv("FARSIDE_CF_ENABLED")
+	if len(cfEnabledVar) > 0 && cfEnabledVar == "1" {
+		cloudflareEnabled = true
+	}
+
+	serviceJSON := noCFServicesJSON
+	if cloudflareEnabled {
+		serviceJSON = fullServicesJSON
+	}
+
+	return serviceJSON
+}
+
+
+func FetchServicesFile(serviceJSON string) ([]byte, error) {
+	resp, err := http.Get(baseRepoLink + serviceJSON)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+
+	bodyBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	err = os.WriteFile(serviceJSON, bodyBytes, 0666)
+	if err != nil {
+		return nil, err
+	}
+
+	return bodyBytes, nil
+}
+
+func InitializeServices() error {
+	serviceJSON := GetServicesFileName()
+	fileBytes, err := os.ReadFile(serviceJSON)
+	if err != nil {
+		fileBytes, err = FetchServicesFile(serviceJSON)
+		if err != nil {
+			return err
+		}
+	}
+
+	err = ingestServicesList(fileBytes)
+	if err != nil {
+		return err
+	}
+
+	FallbackMap = make(map[string]string)
+	for _, serviceElement := range ServiceList {
+		FallbackMap[serviceElement.Type] = serviceElement.Fallback
+	}
+
+	return nil
+}