package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

func main() {
	if len(os.Args) != 3 {
		fmt.Println("Usage: go run main.go <input_directory> <output_directory>")
		return
	}

	inputDir := os.Args[1]
	outputDir := os.Args[2]
	files, err := getGoFiles(inputDir)
	if err != nil {
		fmt.Println(err)
		return
	}

	for _, file := range files {
		typeDecls, importDecls, err := extractTypes(file)
		if err != nil {
			fmt.Println(err)
			continue
		}

		// Filter out structs with "Nullable" at the beginning of their names.
		typeDecls = filterNullableTypes(typeDecls)

		// Generate the adapted file name by inserting the "_adapted" string before the ".go" extension of the original file name.
		adaptedFile := strings.Replace(filepath.Base(file), ".go", "_adapted.go", 1)
		adaptedFile = filepath.Join(outputDir, adaptedFile)
		// Write the struct declarations and import declarations to the adapted file.
		err = writeStruct(typeDecls, importDecls, adaptedFile)
		if err != nil {
			fmt.Println(err)
			continue
		}

		// Reformat the adapted file using gofmt.
		err = runGoImports(adaptedFile)
		if err != nil {
			fmt.Println(err)
			continue
		}
	}
}

// getGoFiles returns a list of .go files in the given directory.
func getGoFiles(dir string) ([]string, error) {
	var files []string

	f, err := os.Open(dir)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	fi, err := f.Readdir(-1)
	if err != nil {
		return nil, err
	}

	for _, file := range fi {
		if !file.IsDir() && strings.HasSuffix(file.Name(), ".go") {
			// Concatenate the directory path and the file name to get the full path.
			files = append(files, dir+"/"+file.Name())
		}
	}

	return files, nil
}

// filterNullableTypes filters out structs with "Nullable" at the beginning of their names.
func filterNullableTypes(structDecls []string) []string {
	var filteredStructDecls []string
	for _, s := range structDecls {
		// Check if the struct name starts with "Nullable".
		if !strings.HasPrefix(s, "type Nullable") {
			filteredStructDecls = append(filteredStructDecls, s)
		}
	}
	return filteredStructDecls
}

// extractTypes reads a .go file and returns a list of type declarations and a list of import declarations.
func extractTypes(file string) ([]string, []string, error) {
	var typeDecls []string
	var importDecls []string

	f, err := os.Open(file)
	if err != nil {
		return nil, nil, err
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	var typeDecl, importDecl string
	inStruct, inImport := false, false
	for scanner.Scan() {
		line := scanner.Text()
		if strings.HasPrefix(line, "import") {
			inImport = true
			importDecl = line + "\n"
		} else if inImport && (line == "" || strings.HasPrefix(line, ")")) {
			importDecl += line + "\n"
			inImport = false
			importDecls = append(importDecls, importDecl)
		} else if inImport {
			importDecl += line + "\n"
		} else if strings.HasPrefix(line, "type") {
			inStruct = true
			typeDecl = line + "\n"
		} else if inStruct && strings.HasPrefix(line, "}") {
			typeDecl += line + "\n"
			typeDecls = append(typeDecls, typeDecl)
			inStruct = false
		} else if inStruct {
			typeDecl += line + "\n"
		}
	}

	if err := scanner.Err(); err != nil {
		return nil, nil, err
	}

	return typeDecls, importDecls, nil
}

// writeStruct writes the given struct declarations and import declarations to a new file with the given name.
func writeStruct(structDecls []string, importDecls []string, file string) error {
	f, err := os.Create(file)
	if err != nil {
		return err
	}
	defer f.Close()

	// Add the package dto declaration at the top of the file.
	_, err = io.WriteString(f, "package dto\n\n")
	if err != nil {
		return err
	}

	// Write the import declarations to the file.
	for _, importDecl := range importDecls {
		_, err = io.WriteString(f, importDecl)
		if err != nil {
			return err
		}
	}

	// Write the struct declarations to the file.
	for _, s := range structDecls {
		_, err = io.WriteString(f, s)
		if err != nil {
			return err
		}
	}

	return nil
}

// runimports reformats the given file using the goimports tool.
func runGoImports(file string) error {
	cmd := exec.Command("goimports", "-w", file)
	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("%s: %s", err, output)
	}
	return nil
}