package apply

import (
	"archive/tar"
	"bytes"
	"compress/gzip"
	"context"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"os"
	"strings"
	"testing"

	"github.com/novox/mesh-host/internal/declaration"
	"github.com/novox/mesh-host/internal/store"
)

// The shapes added so that most of what a person installs is expressible.
//
// A shell, a chat client, a desktop are a package plus configuration in somebody's home, and a
// mesh with no user can manage /etc and nothing anybody looks at.

func declare(t *testing.T, resources string) *declaration.Declaration {
	t.Helper()
	d, err := declaration.Parse([]byte(`{"declaration":1,"resources":[` + resources + `]}`))
	if err != nil {
		t.Fatal(err)
	}
	return d
}

func TestAFileMayBeBytesRatherThanText(t *testing.T) {
	// A wallpaper, a font, an icon. Stored as its own encoding it would be a wallpaper nothing
	// can open.
	dir := t.TempDir()
	original := []byte{0x89, 'P', 'N', 'G', 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0xff}
	d := declare(t, `{"id":"w","type":"file","path":"`+dir+`/wall.png","bytes":"`+
		base64.StdEncoding.EncodeToString(original)+`"}`)

	if _, _, err := Apply(context.Background(), archHost(t), d, store.State{},
		store.OriginCarried, noServices, nil, nil); err != nil {
		t.Fatal(err)
	}
	on, err := os.ReadFile(dir + "/wall.png")
	if err != nil {
		t.Fatal(err)
	}
	if !bytes.Equal(on, original) {
		t.Fatalf("the bytes did not survive: %x", on)
	}
}

func TestAFileSaysWhatIsInItExactlyOnce(t *testing.T) {
	// Three ways of saying it and no precedence between them, so "what is in this file" is
	// answerable by looking rather than by knowing which field wins.
	_, err := declaration.Parse([]byte(`{"declaration":1,"resources":[
		{"id":"f","type":"file","path":"/etc/x","content":"a","bytes":"YQ=="}]}`))
	if err == nil {
		t.Fatal("a file that was both text and bytes was accepted")
	}
	if !strings.Contains(err.Error(), "exactly once") {
		t.Fatalf("unhelpful refusal: %v", err)
	}
}

func TestBytesThatAreNotBase64AreRefused(t *testing.T) {
	dir := t.TempDir()
	d := declare(t, `{"id":"w","type":"file","path":"`+dir+`/x","bytes":"not base64!!"}`)
	_, _, err := Apply(context.Background(), archHost(t), d, store.State{},
		store.OriginCarried, noServices, nil, nil)
	if err == nil {
		t.Fatal("a file carrying nonsense was written")
	}
	if _, statErr := os.Stat(dir + "/x"); statErr == nil {
		t.Fatal("something was written before the failure")
	}
}

// A gzipped tar, and its digest, built here so the test does not depend on a fixture nobody can
// regenerate.
func anArchive(t *testing.T, files map[string]string) ([]byte, string) {
	t.Helper()
	var raw bytes.Buffer
	zipped := gzip.NewWriter(&raw)
	writer := tar.NewWriter(zipped)
	for name, body := range files {
		if err := writer.WriteHeader(&tar.Header{
			Name: name, Mode: 0o644, Size: int64(len(body)), Typeflag: tar.TypeReg,
		}); err != nil {
			t.Fatal(err)
		}
		if _, err := writer.Write([]byte(body)); err != nil {
			t.Fatal(err)
		}
	}
	if err := writer.Close(); err != nil {
		t.Fatal(err)
	}
	if err := zipped.Close(); err != nil {
		t.Fatal(err)
	}
	sum := sha256.Sum256(raw.Bytes())
	return raw.Bytes(), "sha256:" + hex.EncodeToString(sum[:])
}

func serving(t *testing.T, body []byte) string {
	t.Helper()
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		_, _ = w.Write(body)
	}))
	t.Cleanup(server.Close)
	return server.URL + "/theme.tar.gz"
}

func TestAnArchiveIsUnpacked(t *testing.T) {
	body, digest := anArchive(t, map[string]string{
		"config/theme.conf": "dark", "config/icons/one.svg": "<svg/>",
	})
	dir := t.TempDir()
	d := declare(t, `{"id":"theme","type":"archive","source":"`+serving(t, body)+
		`","digest":"`+digest+`","path":"`+dir+`/theme"}`)

	report, _, err := Apply(context.Background(), archHost(t), d, store.State{},
		store.OriginCarried, noServices, nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	if !report.Changed() {
		t.Fatal("nothing changed")
	}
	on, err := os.ReadFile(dir + "/theme/config/theme.conf")
	if err != nil {
		t.Fatal(err)
	}
	if string(on) != "dark" {
		t.Fatalf("got %q", on)
	}
}

func TestAnArchiveThatIsNotWhatWasDeclaredIsRefusedBeforeAnythingIsWritten(t *testing.T) {
	// The only thing making bytes from a network the mesh does not control safe to unpack is
	// that they hash to what was declared.
	body, _ := anArchive(t, map[string]string{"a": "b"})
	dir := t.TempDir()
	d := declare(t, `{"id":"theme","type":"archive","source":"`+serving(t, body)+
		`","digest":"sha256:`+strings.Repeat("ab", 32)+`","path":"`+dir+`/theme"}`)

	_, _, err := Apply(context.Background(), archHost(t), d, store.State{},
		store.OriginCarried, noServices, nil, nil)
	if err == nil {
		t.Fatal("an archive that was not what was declared was unpacked")
	}
	if entries, _ := os.ReadDir(dir); len(entries) != 0 {
		t.Fatal("something was written before the digest was checked")
	}
}

func TestAnArchiveCannotWriteOutsideWhereItWasUnpacked(t *testing.T) {
	// The oldest bug in unpacking. Checked against the resolved root rather than by looking for
	// "..", because there is more than one way to name a path that escapes.
	body, digest := anArchive(t, map[string]string{"../../escaped": "no"})
	dir := t.TempDir()
	d := declare(t, `{"id":"theme","type":"archive","source":"`+serving(t, body)+
		`","digest":"`+digest+`","path":"`+dir+`/theme"}`)

	_, _, err := Apply(context.Background(), archHost(t), d, store.State{},
		store.OriginCarried, noServices, nil, nil)
	if err != nil && !strings.Contains(err.Error(), "outside") {
		t.Fatalf("refused for the wrong reason: %v", err)
	}
	if _, statErr := os.Stat(dir + "/escaped"); statErr == nil {
		t.Fatal("a file landed outside the directory it was unpacked into")
	}
	if err == nil {
		t.Fatal("an escaping entry was accepted")
	}
}

func TestAnUnpackedArchiveIsNotFetchedAgainForNothing(t *testing.T) {
	// The digest is the whole identity of an archive, so a matching record means the tree came
	// from these exact bytes. Applying twice must not report work.
	body, digest := anArchive(t, map[string]string{"a": "b"})
	dir := t.TempDir()
	d := declare(t, `{"id":"theme","type":"archive","source":"`+serving(t, body)+
		`","digest":"`+digest+`","path":"`+dir+`/theme"}`)

	_, state, err := Apply(context.Background(), archHost(t), d, store.State{},
		store.OriginCarried, noServices, nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	again, _, err := Apply(context.Background(), archHost(t), d, state,
		store.OriginCarried, noServices, nil, nil)
	if err != nil {
		t.Fatal(err)
	}
	if again.Changed() {
		said, _ := json.Marshal(again)
		t.Fatalf("the second apply did work: %s", said)
	}
}

func TestAnArchiveWithSomethingThatIsNotAFileIsRefused(t *testing.T) {
	// A theme needing a symlink would otherwise arrive silently incomplete, and a device node in
	// an archive is not something to unpack quietly onto a machine.
	var raw bytes.Buffer
	zipped := gzip.NewWriter(&raw)
	writer := tar.NewWriter(zipped)
	if err := writer.WriteHeader(&tar.Header{
		Name: "link", Typeflag: tar.TypeSymlink, Linkname: "/etc/passwd", Mode: 0o777,
	}); err != nil {
		t.Fatal(err)
	}
	writer.Close()
	zipped.Close()
	sum := sha256.Sum256(raw.Bytes())
	digest := "sha256:" + hex.EncodeToString(sum[:])

	dir := t.TempDir()
	d := declare(t, `{"id":"theme","type":"archive","source":"`+serving(t, raw.Bytes())+
		`","digest":"`+digest+`","path":"`+dir+`/theme"}`)
	_, _, err := Apply(context.Background(), archHost(t), d, store.State{},
		store.OriginCarried, noServices, nil, nil)
	if err == nil {
		t.Fatal("a symlink was unpacked")
	}
	if !strings.Contains(err.Error(), "files and directories") {
		t.Fatalf("refused for the wrong reason: %v", err)
	}
}

func TestAnArchiveMustBePinned(t *testing.T) {
	_, err := declaration.Parse([]byte(`{"declaration":1,"resources":[
		{"id":"t","type":"archive","source":"https://example.invalid/a.tgz","path":"/opt/t"}]}`))
	if err == nil {
		t.Fatal("an unpinned archive was accepted")
	}
	if !strings.Contains(err.Error(), "digest") {
		t.Fatalf("unhelpful refusal: %v", err)
	}
}