package httpdl

import (
	"context"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"testing"

	"github.com/hanbok/got/download"
)

// TestConditionalGet304 checks that --conditional-get sends If-Modified-Since
// for an existing local file and treats a 304 as success without rewriting the
// file.
func TestConditionalGet304(t *testing.T) {
	dir := t.TempDir()
	out := filepath.Join(dir, "file.bin")
	const existing = "already here"
	if err := os.WriteFile(out, []byte(existing), 0o644); err != nil {
		t.Fatal(err)
	}

	gotIfModSince := false
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Header.Get("If-Modified-Since") != "" {
			gotIfModSince = true
		}
		w.WriteHeader(http.StatusNotModified)
	}))
	defer srv.Close()

	d := New([]string{srv.URL + "/file.bin"}, Config{
		Dir:              dir,
		Out:              "file.bin",
		MaxConnPerServer: 1,
		ConditionalGet:   true,
		AllowOverwrite:   true,
		UserAgent:        "got-test",
	})
	if err := d.Run(context.Background()); err != nil {
		t.Fatalf("conditional-get 304 should succeed, got %v", err)
	}
	if !gotIfModSince {
		t.Fatal("expected an If-Modified-Since header on the request")
	}
	if d.Stat().Status != download.Complete {
		t.Fatalf("status = %v, want Complete", d.Stat().Status)
	}
	// The file must be untouched: 304 means "up to date".
	b, err := os.ReadFile(out)
	if err != nil {
		t.Fatal(err)
	}
	if string(b) != existing {
		t.Fatalf("file was rewritten: %q, want %q", b, existing)
	}
}

// TestConditionalGetSkippedWithControlFile verifies the rule that
// --conditional-get is ignored when a .got control file exists, so an
// in-progress resume is never short-circuited by a 304.
func TestConditionalGetSkippedWithControlFile(t *testing.T) {
	dir := t.TempDir()
	out := filepath.Join(dir, "file.bin")
	if err := os.WriteFile(out, []byte("partial"), 0o644); err != nil {
		t.Fatal(err)
	}
	// A control file present means a resume is in flight.
	if err := os.WriteFile(controlPath(out), []byte("{}"), 0o644); err != nil {
		t.Fatal(err)
	}

	sawIfModSince := false
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Header.Get("If-Modified-Since") != "" {
			sawIfModSince = true
		}
		// Serve a small body so the run can complete.
		http.Error(w, "no range", http.StatusOK)
	}))
	defer srv.Close()

	d := New([]string{srv.URL + "/file.bin"}, Config{
		Dir:              dir,
		Out:              "file.bin",
		MaxConnPerServer: 1,
		ConditionalGet:   true,
		AllowOverwrite:   true,
		UserAgent:        "got-test",
	})
	_ = d.Run(context.Background())
	if sawIfModSince {
		t.Fatal("If-Modified-Since must not be sent when a control file exists")
	}
}