package pierre

import (
	"github.com/google/go-cmp/cmp"
	"strings"
	"testing"
)

func TestSplitDiffIntoChunks_SmallDiff(t *testing.T) {
	diff := "diff --git a/file1.txt b/file1.txt\n+added line\n"
	max := 1000
	chunks := splitDiffIntoChunks([]byte(diff), max)
	if got, want := len(chunks), 1; got != want {
		t.Fatalf("expected %d chunk, got %d", want, got)
	}
	if diff != chunks[0] {
		t.Fatalf("chunk content changed: %s", diff)
	}
}

func TestSplitDiffIntoChunks_MultipleFiles(t *testing.T) {
	diff := "diff --git a/file1.txt b/file1.txt\n+added line 1\n" +
		"diff --git a/file2.txt b/file2.txt\n+added line 2\n"
	max := 50 // each file diff is less than this, but total exceeds
	chunks := splitDiffIntoChunks([]byte(diff), max)
	if got, want := len(chunks), 2; got != want {
		t.Fatalf("expected %d chunks, got %d", want, got)
	}
	// Ensure each chunk starts with the proper file header
	if !strings.HasPrefix(chunks[0], "diff --git a/file1.txt") {
		t.Fatalf("first chunk does not contain file1 header: %s", chunks[0])
	}
	if !strings.HasPrefix(chunks[1], "diff --git a/file2.txt") {
		t.Fatalf("second chunk does not contain file2 header: %s", chunks[1])
	}
}

func TestSplitDiffIntoChunks_LargeSingleFile(t *testing.T) {
	// Create a diff that exceeds maxSize by repeating a line
	line := "+very long added line that will be repeated many times to exceed the chunk size\n"
	diff := "diff --git a/large.txt b/large.txt\n" + strings.Repeat(line, 200)
	max := 500 // small limit
	chunks := splitDiffIntoChunks([]byte(diff), max)
	// Ensure no chunk exceeds max size
	for i, c := range chunks {
		if len(c) > max {
			t.Fatalf("chunk %d exceeds max size: %d > %d", i, len(c), max)
		}
	}
	// Recombine chunks and compare to original (ignoring possible split boundaries)
	recombined := strings.Join(chunks, "")
	if diff != recombined {
		if d := cmp.Diff(diff, recombined); d != "" {
			t.Fatalf("recombined diff differs:\n%s", d)
		}
	}
}