package store

import (
	"bytes"
	"io"
	"net/http"
	"net/http/httptest"
	"testing"
	"time"
)

// A reader over an in-memory slice, counting the fetches a query would cost.
func testReader(data []byte, chunk int64) (*chunkReader, *int) {
	calls := 0
	return newChunkReader(int64(len(data)), chunk, func(off, n int64) ([]byte, error) {
		calls++
		return data[off : off+n], nil
	}), &calls
}

func TestChunkReader(t *testing.T) {
	data := make([]byte, 3<<20+7)
	for i := range data {
		data[i] = byte(i * 31)
	}
	r, calls := testReader(data, 1000)
	got, err := io.ReadAll(r)
	if err != nil || !bytes.Equal(got, data) {
		t.Fatalf("ReadAll: err %v, %d bytes", err, len(got))
	}
	if want := (len(data) + 999) / 1000; *calls != want {
		t.Errorf("%d fetches, want %d", *calls, want)
	}
	if n, _ := r.Seek(0, io.SeekEnd); n != int64(len(data)) {
		t.Errorf("SeekEnd = %d", n)
	}
	if _, err := r.Seek(-1, io.SeekStart); err == nil {
		t.Error("negative seek should fail")
	}
	r.Seek(1500, io.SeekStart)
	buf := make([]byte, 1200)
	if _, err := io.ReadFull(r, buf); err != nil || !bytes.Equal(buf, data[1500:2700]) {
		t.Errorf("read after seek: %v", err)
	}
	if _, err := r.Read(buf); r.off != 2700 && err != nil {
		t.Errorf("continuing read: %v", err)
	}
}

func TestChunkReaderServeContent(t *testing.T) {
	data := bytes.Repeat([]byte("0123456789"), 500)
	r, calls := testReader(data, 512)
	w := httptest.NewRecorder()
	req := httptest.NewRequest("GET", "/media/x", nil)
	req.Header.Set("Range", "bytes=1500-2499")
	http.ServeContent(w, req, "x.bin", time.Now(), r)
	if w.Code != http.StatusPartialContent || !bytes.Equal(w.Body.Bytes(), data[1500:2500]) || w.Header().Get("Content-Range") != "bytes 1500-2499/5000" {
		t.Errorf("range: code %d, %d bytes, %s", w.Code, w.Body.Len(), w.Header().Get("Content-Range"))
	}
	if *calls != 2 {
		t.Errorf("a 1000-byte range cost %d fetches, want 2", *calls)
	}
	r, calls = testReader(data, 512)
	w = httptest.NewRecorder()
	http.ServeContent(w, httptest.NewRequest("HEAD", "/media/x", nil), "x.bin", time.Now(), r)
	if w.Code != http.StatusOK || w.Header().Get("Content-Length") != "5000" || *calls != 0 {
		t.Errorf("HEAD: code %d, length %s, %d fetches", w.Code, w.Header().Get("Content-Length"), *calls)
	}
}