From 4a1b6faf26ede830e84b9903651ce673327b43ba Mon Sep 17 00:00:00 2001
From: Eduardo Cuducos <4732915+cuducos@users.noreply.github.com>
Date: Tue, 27 Feb 2024 15:36:03 -0500
Subject: [PATCH] Adds mirror download option

Closes #206
---
 cmd/download.go      |  5 ++++
 docs/servidor.md     |  5 ++++
 download/download.go | 12 +++++++++
 download/mirror.go   | 60 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 82 insertions(+)
 create mode 100644 download/mirror.go

diff --git a/cmd/download.go b/cmd/download.go
index 1c14b40f..5f898547 100644
--- a/cmd/download.go
+++ b/cmd/download.go
@@ -36,6 +36,7 @@ var (
 	chunkSize         int64
 	skipExistingFiles bool
 	restart           bool
+	mirror            string
 )
 
 var downloadCmd = &cobra.Command{
@@ -50,6 +51,9 @@ var downloadCmd = &cobra.Command{
 		if err != nil {
 			return err
 		}
+		if mirror != "" {
+			return download.DownloadFromMirror(mirror, dir, dur, skipExistingFiles, restart, parallelDownloads, downloadRetries, chunkSize)
+		}
 		return download.Download(dir, dur, skipExistingFiles, restart, parallelDownloads, downloadRetries, chunkSize)
 	},
 }
@@ -93,6 +97,7 @@ func downloadCLI() *cobra.Command {
 	downloadCmd.Flags().IntVarP(&parallelDownloads, "parallel", "p", download.DefaultMaxParallel, "maximum parallel downloads")
 	downloadCmd.Flags().Int64VarP(&chunkSize, "chunk-size", "c", download.DefaultChunkSize, "max length of the bytes range for each HTTP request")
 	downloadCmd.Flags().BoolVarP(&restart, "restart", "e", false, "restart all downloads from the beginning")
+	downloadCmd.Flags().StringVarP(&mirror, "mirror", "m", "", "download from the mirror, not from the original source (YYYY-MM-DD)")
 	return downloadCmd
 }
 
diff --git a/docs/servidor.md b/docs/servidor.md
index 9fd1d61a..58ef4ee2 100644
--- a/docs/servidor.md
+++ b/docs/servidor.md
@@ -29,6 +29,10 @@ Caso o download falhe, é recomendado variar as configurações explicadas no `-
 
 Em último caso, é possível listar as URLs para download dos arquivos com comando `urls`; e, então, tentar fazer o download de outra forma (manualmente, com alguma ferramenta que permite recomeçar downloads interrompidos, etc.).
 
+### Espelho dos dados
+
+O _Minha Receita_ mantém um [espelho dos dados em uma diretório compartilhado](https://mirror.minhareceita.org). Você pode fazer o download dos arquivos de lá (ao invés de utilisar o servidor oficial) com a opção `--mirror YYYY-MM-DD` substituindo a data por alguma das disponíveis no espelho.
+
 ### Exemplos de uso
 
 Sem Docker:
@@ -36,6 +40,7 @@ Sem Docker:
 ```console
 $ minha-receita download --urls-only
 $ minha-receita download --timeout 1h42m12s
+$ minha-receita download --mirror 2022-12-17
 ```
 
 Com Docker:
diff --git a/download/download.go b/download/download.go
index 1971ac76..0a0e1527 100644
--- a/download/download.go
+++ b/download/download.go
@@ -75,6 +75,18 @@ func Download(dir string, timeout time.Duration, skip, restart bool, parallel in
 	return nil
 }
 
+// Download all the files from the project's mirror
+func DownloadFromMirror(mirror string, dir string, timeout time.Duration, skip, restart bool, parallel int, retries uint, chunkSize int64) error {
+	urls, err := getMirrorURLs(mirror)
+	if err != nil {
+		return fmt.Errorf("error getting mirror urls: %w", err)
+	}
+	if err := download(dir, urls, parallel, retries, chunkSize, timeout, restart); err != nil {
+		return fmt.Errorf("error downloading files from the mirror: %w", err)
+	}
+	return nil
+}
+
 // URLs shows the URLs to be downloaded.
 func URLs(dir string, skip bool) error {
 	urls := []string{federalRevenueURL, nationalTreasureBaseURL}
diff --git a/download/mirror.go b/download/mirror.go
new file mode 100644
index 00000000..afa713d5
--- /dev/null
+++ b/download/mirror.go
@@ -0,0 +1,60 @@
+package download
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+const mirrorURL = "https://mirror.minhareceita.org"
+
+// TODO: do we need to export these structs?
+type MirrorFile struct {
+	URL  string `json:"url"`
+	Size uint   `json:"size"`
+}
+
+type MirrorGroup struct {
+	Name string       `json:"name"`
+	URLs []MirrorFile `json:"urls"`
+}
+
+type MirrorResponse struct {
+	Data []MirrorGroup `json:"data"`
+}
+
+func getMirrorURLs(t string) ([]string, error) {
+	c := &http.Client{}
+	req, err := http.NewRequest("GET", mirrorURL, nil)
+	if err != nil {
+		return []string{}, fmt.Errorf("error creating request for mirror: %w", err)
+	}
+	req.Header.Set("Accept", "application/json")
+	r, err := c.Do(req)
+	if err != nil {
+		return []string{}, fmt.Errorf("error sending request to mirror: %w", err)
+	}
+	defer r.Body.Close()
+	var gs MirrorResponse
+	if err = json.NewDecoder(r.Body).Decode(&gs); err != nil {
+		return []string{}, fmt.Errorf("error decoding response body: %w", err)
+	}
+	var urls []string
+	var opts []string
+	for _, g := range gs.Data {
+		if g.Name == t {
+			for _, u := range g.URLs {
+				if u.Size > 0 {
+					urls = append(urls, u.URL)
+				}
+			}
+			break
+		}
+		opts = append(opts, g.Name)
+	}
+	if len(urls) == 0 {
+		return []string{}, fmt.Errorf("unknown mirror identifier `%s`, options are: %s", t, strings.Join(opts, ", "))
+	}
+	return urls, nil
+}