package main

import (
	"embed"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"text/template"
	"io"
)

//go:embed templates/tex/*
var templates embed.FS

func main() {
	var input, output string

	flag.StringVar(&input, "input", "", "specify the CV JSON file that you want to input to the builder.")
	flag.StringVar(&output, "output", "", "specify the name of the output CV file.")
	flag.Parse()

	tempDir, err := os.MkdirTemp("/tmp", "cv-builder-")
	if err != nil {
		log.Fatalf("ERROR: Unable to create a temporary directory; %v", err)
	}

	defer func() {
		err := os.RemoveAll(tempDir)
		if err != nil {
			log.Printf("WARN: An error occurred when removing the temporary directory; %v", err)
		}
	}()

	texFile, err := tex(input, tempDir)
	if err != nil {
		log.Fatalf("ERROR: %v", err)
	}

	if err := pdf(tempDir, texFile, output); err != nil {
		log.Fatalf("ERROR: %v", err)
	}
}

// tex generates the CV document as a Tex file.
func tex(input, tempDir string) (string, error) {
	data, err := os.ReadFile(input)
	if err != nil {
		return "", fmt.Errorf("unable to read data from file; %w", err)
	}

	var cv Cv
	if err = json.Unmarshal(data, &cv); err != nil {
		return "", fmt.Errorf("unable to decode JSON data; %w", err)
	}

	output := filepath.Join(tempDir, "cv.tex")

	file, err := os.Create(output)
	if err != nil {
		return "", fmt.Errorf("unable to create output file %s; %w", output, err)
	}
	defer file.Close()

	fmap := template.FuncMap{
		"notLastElement":   notLastElement,
		"join":             join,
		"durationToString": durationToString,
	}

	t := template.Must(template.New("cv.tmpl.tex").
		Funcs(fmap).
		Delims("<<", ">>").
		ParseFS(templates, "templates/tex/*.tmpl.tex"),
	)

	if err = t.Execute(file, cv); err != nil {
		return "", fmt.Errorf("unable to execute the CV template. %w", err)
	}

	log.Printf("INFO: Tex file %s was successfully created.", output)

	return output, nil
}

// pdf generates the CV document as a PDF file from the tex file.
func pdf(tempDir, texFile, output string) error {
	pathArg := "--path=" + tempDir

	command := exec.Command("mtxrun", pathArg, "--script", "context", texFile)

	command.Stderr = os.Stderr
	command.Stdout = os.Stdout

	if err := command.Run(); err != nil {
		return err
	}

	if output == "" {
		output = "./cv.pdf"
	}

	if err := copy(filepath.Join(tempDir, "cv.pdf"), output); err != nil {
		return err
	}

	return nil
}

func copy(input, output string) error {
	inputFile, err := os.Open(input)
	if err != nil {
		return fmt.Errorf("unable to open %s; %w", input, err)
	}
	defer inputFile.Close()

	outputFile, err := os.Create(output)
	if err != nil {
		return fmt.Errorf("unable to create %s; %w", output, err)
	}
	defer outputFile.Close()

	_, err = io.Copy(outputFile, inputFile)
	if err != nil {
		return fmt.Errorf("unable to copy %s to %s; %w", input, output, err)
	}

	return nil
}