// Fenrir console screen reader.
// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along with
// this program. If not, see <https://www.gnu.org/licenses/gpl-3.0.html>.

//go:build linux && cgo

package console

import (
	"bytes"
	"errors"
	"io"
	"testing"
)

type unicodeReader struct {
	*bytes.Reader
	requests []int
	limit    int
}

func (r *unicodeReader) Read(data []byte) (int, error) {
	r.requests = append(r.requests, len(data))
	if r.limit > 0 && len(data) > r.limit {
		data = data[:r.limit]
	}
	return r.Reader.Read(data)
}

func TestUnicodeReadBoundedAlignedAndComplete(t *testing.T) {
	const cells = 80 * 25
	for _, size := range []int{0, 4, cells*4 - 4, cells * 4, cells*4 + 4, cells * 8} {
		for _, limit := range []int{0, 128} {
			reader := &unicodeReader{Reader: bytes.NewReader(make([]byte, size)), limit: limit}
			data, err := read_unicode(reader, cells)
			if err != nil || len(data) != min(size, (cells+1)*4) {
				t.Fatalf("size %d limit %d: got %d bytes, %v", size, limit, len(data), err)
			}
			for _, request := range reader.requests {
				if request%4 != 0 {
					t.Fatalf("unaligned request: %d", request)
				}
			}
			if limit == 0 && len(reader.requests) > 2 {
				t.Fatalf("unnecessary reads: %v", reader.requests)
			}
		}
	}
}

type failedReader struct{}

func (failedReader) Read([]byte) (int, error) { return 0, io.ErrClosedPipe }

func TestUnicodeReadPreservesIOError(t *testing.T) {
	if _, err := read_unicode(failedReader{}, 80*25); !errors.Is(err, io.ErrClosedPipe) {
		t.Fatalf("lost I/O error: %v", err)
	}
}