package gitea

import (
	"context"
	"errors"
	"math"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
	"time"
)

func TestGetPullRequestDiff_SizeLimits(t *testing.T) {
	tests := []struct {
		name        string
		diff        string
		maxDiffSize int64
		wantErr     error
		wantDiff    string
	}{
		{
			name:        "exceeds max size",
			diff:        strings.Repeat("+ added line\n", 1000), // ~13 KB
			maxDiffSize: 100,
			wantErr:     ErrDiffTooLarge,
		},
		{
			name:        "within max size",
			diff:        "diff --git a/f.go b/f.go\n--- a/f.go\n+++ b/f.go\n@@ -1 +1 @@\n-old\n+new\n",
			maxDiffSize: 1024,
			wantDiff:    "diff --git a/f.go b/f.go\n--- a/f.go\n+++ b/f.go\n@@ -1 +1 @@\n-old\n+new\n",
		},
		{
			name:        "exactly at limit",
			diff:        strings.Repeat("x", 50),
			maxDiffSize: 50,
			wantDiff:    strings.Repeat("x", 50),
		},
		{
			name:        "one byte over limit",
			diff:        strings.Repeat("x", 51),
			maxDiffSize: 50,
			wantErr:     ErrDiffTooLarge,
		},
		{
			name:        "disabled limit",
			diff:        strings.Repeat("x", 10000),
			maxDiffSize: -1,
			wantDiff:    strings.Repeat("x", 10000),
		},
		{
			name:        "math.MaxInt64 treated as disabled",
			diff:        strings.Repeat("x", 10000),
			maxDiffSize: math.MaxInt64,
			wantDiff:    strings.Repeat("x", 10000),
		},
		{
			name:        "default limit",
			diff:        "diff content",
			maxDiffSize: 0, // zero means use DefaultMaxDiffSize
			wantDiff:    "diff content",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
				w.Write([]byte(tt.diff)) //nolint:errcheck // test handler
			}))
			defer server.Close()

			client := NewTestClient(server.URL, "test-token")
			client.MaxDiffSize = tt.maxDiffSize
			client.RetryBackoff = []time.Duration{}

			got, err := client.GetPullRequestDiff(context.Background(), "owner", "repo", 1)

			if tt.wantErr != nil {
				if err == nil {
					t.Fatal("expected error, got nil")
				}
				if !errors.Is(err, tt.wantErr) {
					t.Errorf("expected %v, got: %v", tt.wantErr, err)
				}
				return
			}

			if err != nil {
				t.Fatalf("unexpected error: %v", err)
			}
			if got != tt.wantDiff {
				t.Errorf("diff mismatch: got length %d, want length %d", len(got), len(tt.wantDiff))
			}
		})
	}
}