package publicrelease

import (
	"context"
	"crypto/ed25519"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"fmt"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
)

func testFeed(t *testing.T, sign bool, assets map[string][]byte) (Feed, string) {
	t.Helper()
	pub, priv, _ := ed25519.GenerateKey(nil)
	var sums strings.Builder
	for name, body := range assets {
		s := sha256.Sum256(body)
		fmt.Fprintf(&sums, "%s  %s\n", hex.EncodeToString(s[:]), name)
	}
	sig := ed25519.Sign(priv, []byte(sums.String()))
	mux := http.NewServeMux()
	mux.HandleFunc("/latest.txt", func(w http.ResponseWriter, r *http.Request) { fmt.Fprintln(w, "v0.18.0") })
	mux.HandleFunc("/dl/v0.18.0/SHA256SUMS.txt", func(w http.ResponseWriter, r *http.Request) { fmt.Fprint(w, sums.String()) })
	mux.HandleFunc("/dl/v0.18.0/SHA256SUMS.txt.sig", func(w http.ResponseWriter, r *http.Request) {
		if sign {
			fmt.Fprintln(w, base64.StdEncoding.EncodeToString(sig))
		} else {
			fmt.Fprintln(w, base64.StdEncoding.EncodeToString(make([]byte, ed25519.SignatureSize)))
		}
	})
	for name, body := range assets {
		body := body
		mux.HandleFunc("/dl/v0.18.0/"+name, func(w http.ResponseWriter, r *http.Request) { w.Write(body) })
	}
	ts := httptest.NewServer(mux)
	t.Cleanup(ts.Close)
	return Feed{LatestURL: ts.URL + "/latest.txt", DownloadBase: ts.URL + "/dl", PubKey: base64.StdEncoding.EncodeToString(pub)}, ts.URL
}

func TestFeedLatestAndVerifiedAsset(t *testing.T) {
	body := []byte("ELF arm64")
	f, _ := testFeed(t, true, map[string][]byte{"carlos-linux-arm64": body, "carlos-linux-amd64": []byte("ELF amd64")})
	ctx := context.Background()
	tag, err := f.Latest(ctx)
	if err != nil || tag != "v0.18.0" {
		t.Fatalf("latest = %q %v", tag, err)
	}
	data, sha, err := f.Asset(ctx, tag, AssetName("linux-arm64"), 1<<20)
	if err != nil || string(data) != string(body) {
		t.Fatalf("asset: %v", err)
	}
	s := sha256.Sum256(body)
	if sha != hex.EncodeToString(s[:]) {
		t.Fatalf("sha = %s", sha)
	}
	if _, _, err := f.Asset(ctx, tag, "carlos-windows-amd64.zip", 1<<20); err == nil {
		t.Fatal("an asset absent from the sums was accepted")
	}
}

func TestFeedRefusesABadSignatureAndATamperedAsset(t *testing.T) {
	body := []byte("ELF")
	f, _ := testFeed(t, false, map[string][]byte{"carlos-linux-arm64": body})
	if _, err := f.Sums(context.Background(), "v0.18.0"); err == nil || !strings.Contains(err.Error(), "signature") {
		t.Fatalf("bad signature: %v", err)
	}
	// Signed sums, but the served asset differs from the sum.
	f2, _ := testFeed(t, true, map[string][]byte{"carlos-linux-arm64": body})
	// Simulate tampering by asking for a limit smaller than the asset: the
	// truncated download cannot match its sum.
	if _, _, err := f2.Asset(context.Background(), "v0.18.0", "carlos-linux-arm64", 1); err == nil {
		t.Fatal("a truncated asset matched its sum")
	}
}

func TestFeedLatestRequiresATag(t *testing.T) {
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { fmt.Fprintln(w, "main") }))
	defer ts.Close()
	f := Feed{LatestURL: ts.URL, DownloadBase: ts.URL, PubKey: ""}
	if _, err := f.Latest(context.Background()); err == nil {
		t.Fatal("accepted a non-tag latest")
	}
}