package fileops

import (
	"fmt"
	"io"
	"math"
	"os"
	"strings"
)

// ReadFileBounded reads at most limit bytes from path using ordinary workspace
// path semantics. It does not return partial data when the limit is exceeded.
func ReadFileBounded(path string, limit int64) ([]byte, error) {
	if strings.TrimSpace(path) == "" {
		return nil, fmt.Errorf("file path is required")
	}
	if limit < 0 {
		return nil, fmt.Errorf("file read limit %d is invalid", limit)
	}
	file, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("open file %q: %w", path, err)
	}
	defer func() { _ = file.Close() }()
	readLimit := limit
	if limit < math.MaxInt64 {
		readLimit++
	}
	data, err := io.ReadAll(io.LimitReader(file, readLimit))
	if err != nil {
		return nil, fmt.Errorf("read file %q: %w", path, err)
	}
	if int64(len(data)) > limit {
		return nil, fmt.Errorf("file %q exceeds %d-byte limit", path, limit)
	}
	return data, nil
}