package cmd

import (
	"flag"
	"fmt"
	"io"
	"log/slog"
	"os"
	"path/filepath"
	"time"

	"codeflow.dananglin.me.uk/apollo/spruce/internal/pdf"
)

type GenerateCommand struct {
	*flag.FlagSet
	summary           string
	input             string
	output            string
	employmentHistory int
	verbose           bool
}

type noInputSpecifiedError struct{}

func (e noInputSpecifiedError) Error() string {
	return "no input file specified, please set the --input field"
}

func NewGenerateCommand() *GenerateCommand {
	gc := GenerateCommand{
		FlagSet: flag.NewFlagSet("generate", flag.ExitOnError),
		summary: "Generate a PDF file from an existing CV JSON file.",
	}

	gc.StringVar(&gc.input, "input", "", "specify the CV JSON file that you want to input to the builder.")
	gc.StringVar(&gc.output, "output", "cv.pdf", "specify the name of the output CV file.")
	gc.IntVar(&gc.employmentHistory, "employment-history", 10, "show employment history within these number of years.")
	gc.BoolVar(&gc.verbose, "verbose", false, "set to true to enable verbose logging.")

	gc.Usage = usageFunc(gc.Name(), gc.summary, gc.FlagSet)

	return &gc
}

func (g *GenerateCommand) Run() error {
	if g.input == "" {
		return noInputSpecifiedError{}
	}

	historyLimit := time.Now().AddDate(-1*g.employmentHistory, 0, 0)

	tempDir, err := os.MkdirTemp("/tmp", "cv-builder-")
	if err != nil {
		return fmt.Errorf("unable to create a temporary directory; %w", err)
	}

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

	pdfFileName, err := pdf.Generate(tempDir, g.input, historyLimit, g.verbose)
	if err != nil {
		return fmt.Errorf("unable to create the PDF file; %w", err)
	}

	if err := copyfile(filepath.Join(tempDir, "cv.pdf"), g.output); err != nil {
		return fmt.Errorf("unable to copy %s to %s; %w", pdfFileName, g.output, err)
	}

	return nil
}

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

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

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

	slog.Info("File successfully copied.", "source", source, "destination", destination)

	return nil
}