package fileops

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

type DeleteResult struct {
	File         string
	DeletedLines []int
}

// DeleteLinesInFile removes all lines matching pattern (fixed string) from the file.
// Returns the original 1-indexed line numbers that were deleted.
func DeleteLinesInFile(path, pattern string, dryRun bool) (DeleteResult, error) {
	result := DeleteResult{File: path}

	f, err := os.Open(path)
	if err != nil {
		return result, err
	}

	var kept []string
	scanner := bufio.NewScanner(f)
	lineNum := 0
	for scanner.Scan() {
		lineNum++
		line := scanner.Text()
		if strings.Contains(line, pattern) {
			result.DeletedLines = append(result.DeletedLines, lineNum)
		} else {
			kept = append(kept, line)
		}
	}
	f.Close()
	if err := scanner.Err(); err != nil {
		return result, err
	}

	if len(result.DeletedLines) == 0 || dryRun {
		return result, nil
	}

	content := ""
	if len(kept) > 0 {
		content = strings.Join(kept, "\n") + "\n"
	}
	return result, atomicWrite(path, content)
}

// DeleteLinesInFileRegex removes lines matching the regex pattern from the file.
func DeleteLinesInFileRegex(path, pattern string, dryRun bool) (DeleteResult, error) {
	result := DeleteResult{File: path}

	f, err := os.Open(path)
	if err != nil {
		return result, err
	}

	re, err := compilePattern(pattern)
	if err != nil {
		f.Close()
		return result, err
	}

	var kept []string
	scanner := bufio.NewScanner(f)
	lineNum := 0
	for scanner.Scan() {
		lineNum++
		line := scanner.Text()
		if re.MatchString(line) {
			result.DeletedLines = append(result.DeletedLines, lineNum)
		} else {
			kept = append(kept, line)
		}
	}
	f.Close()
	if err := scanner.Err(); err != nil {
		return result, err
	}

	if len(result.DeletedLines) == 0 || dryRun {
		return result, nil
	}

	content := ""
	if len(kept) > 0 {
		content = strings.Join(kept, "\n") + "\n"
	}
	return result, atomicWrite(path, content)
}

func PrintDeleteResults(results []DeleteResult) {
	totalFiles := 0
	totalLines := 0
	for _, r := range results {
		if len(r.DeletedLines) == 0 {
			continue
		}
		totalFiles++
		totalLines += len(r.DeletedLines)
		nums := formatLineNums(r.DeletedLines)
		fmt.Printf("%s: deleted lines %s\n", r.File, nums)
	}
	fmt.Printf("%d file(s) modified, %d line(s) deleted.\n", totalFiles, totalLines)
}