package main

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

// applyStandardModifications handles `standard` type patches
func applyStandardModifications(filePath string, modifications []string) error {
	contentBytes, err := os.ReadFile(filePath)
	if err != nil {
		return fmt.Errorf("failed to read file: %v", err)
	}
	lines := strings.Split(string(contentBytes), "\n")

	var delBlock []string
	var addBlock []string
	var patchBlocks []struct {
		del []string
		add []string
	}

	// Group lines into delete and add blocks
	for _, line := range modifications {
		if strings.HasPrefix(line, "-") {
			delBlock = append(delBlock, strings.TrimPrefix(line, "-"))
		} else if strings.HasPrefix(line, "+") {
			addBlock = append(addBlock, strings.TrimPrefix(line, "+"))
		} else if line == "" && len(delBlock) > 0 {
			patchBlocks = append(patchBlocks, struct {
				del []string
				add []string
			}{append([]string{}, delBlock...), append([]string{}, addBlock...)})
			delBlock = nil
			addBlock = nil
		}
	}
	if len(delBlock) > 0 || len(addBlock) > 0 {
		patchBlocks = append(patchBlocks, struct {
			del []string
			add []string
		}{delBlock, addBlock})
	}

	// Apply each block
	for _, patch := range patchBlocks {
		matchIndex := -1
		for i := 0; i <= len(lines)-len(patch.del); i++ {
			matched := true
			for j := range patch.del {
				if strings.TrimSpace(lines[i+j]) != strings.TrimSpace(patch.del[j]) {
					matched = false
					break
				}
			}
			if matched {
				matchIndex = i
				break
			}
		}
		if matchIndex == -1 {
			return fmt.Errorf("patch block not found in file: %v", patch.del)
		}

		// Replace matched block
		newLines := append([]string{}, lines[:matchIndex]...)
		newLines = append(newLines, patch.add...)
		newLines = append(newLines, lines[matchIndex+len(patch.del):]...)
		lines = newLines
	}

	// Write updated file
	return os.WriteFile(filePath, []byte(strings.Join(lines, "\n")), 0644)
}