package update

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"io"
	"log/slog"
	"os"
	"path/filepath"
	"testing"

	"internetpressure.io/probe-agent/internal/protocol"
)

type fakeFetcher struct {
	latest    protocol.AgentLatest
	asset     []byte
	downloads int
}

func (f *fakeFetcher) AgentLatest(context.Context) (*protocol.AgentLatest, error) {
	return &f.latest, nil
}
func (f *fakeFetcher) Download(_ context.Context, _ string, w io.Writer, _ int64) (int64, error) {
	f.downloads++
	n, err := w.Write(f.asset)
	return int64(n), err
}

func TestUpdateReplacesBinary(t *testing.T) {
	dir := t.TempDir()
	exe := filepath.Join(dir, "bin", "ip-probe")
	os.MkdirAll(filepath.Dir(exe), 0o755)
	os.WriteFile(exe, []byte("old"), 0o755)

	newBin := []byte("#!/bin/sh\necho new\n")
	sum := sha256.Sum256(newBin)
	f := &fakeFetcher{asset: newBin, latest: protocol.AgentLatest{Version: "0.2.0",
		Assets: map[string]protocol.Asset{Platform(): {URL: "https://x/ip-probe", SHA256: hex.EncodeToString(sum[:])}}}}
	u := &Updater{Fetcher: f, Version: "0.1.0", DataDir: dir, ExePath: exe, Log: slog.New(slog.DiscardHandler)}

	updated, err := u.Check(context.Background())
	if err != nil || !updated {
		t.Fatalf("updated=%v err=%v", updated, err)
	}
	got, _ := os.ReadFile(exe)
	if string(got) != string(newBin) {
		t.Fatalf("binary not replaced: %q", got)
	}
	if fi, _ := os.Stat(exe); fi.Mode().Perm() != 0o755 {
		t.Fatalf("mode %v", fi.Mode())
	}
	if _, err := os.Stat(filepath.Join(dir, tmpFile)); !errors.Is(err, os.ErrNotExist) {
		t.Fatal("tmp file left behind")
	}
	// Same version offered again (e.g. the new binary crashes and the old one is restored) → not re-attempted.
	os.WriteFile(exe, []byte("old"), 0o755)
	updated, err = u.Check(context.Background())
	if err != nil || updated || f.downloads != 1 {
		t.Fatalf("loop guard failed: updated=%v err=%v downloads=%d", updated, err, f.downloads)
	}
}

func TestUpdateRejectsBadHashAndSameVersion(t *testing.T) {
	dir := t.TempDir()
	exe := filepath.Join(dir, "ip-probe")
	os.WriteFile(exe, []byte("old"), 0o755)
	f := &fakeFetcher{asset: []byte("evil"), latest: protocol.AgentLatest{Version: "0.3.0",
		Assets: map[string]protocol.Asset{Platform(): {URL: "u", SHA256: "00"}}}}
	u := &Updater{Fetcher: f, Version: "0.1.0", DataDir: dir, ExePath: exe, Log: slog.New(slog.DiscardHandler)}
	updated, err := u.Check(context.Background())
	if updated || err == nil {
		t.Fatalf("bad hash accepted: updated=%v err=%v", updated, err)
	}
	if got, _ := os.ReadFile(exe); string(got) != "old" {
		t.Fatal("binary modified despite bad hash")
	}
	// Same version → nothing to do, no download.
	f.latest.Version = "0.1.0"
	f.downloads = 0
	if updated, err := u.Check(context.Background()); updated || err != nil || f.downloads != 0 {
		t.Fatalf("same version: updated=%v err=%v downloads=%d", updated, err, f.downloads)
	}
	// No asset for this platform → skip quietly.
	f.latest = protocol.AgentLatest{Version: "0.4.0", Assets: map[string]protocol.Asset{"plan9-mips": {URL: "u", SHA256: "00"}}}
	if updated, err := u.Check(context.Background()); updated || err != nil {
		t.Fatalf("missing platform: updated=%v err=%v", updated, err)
	}
}