package ocrmypdf

import (
	"bytes"
	"fmt"
	"io"
	"os/exec"
	"strings"
)

type CLI struct {
	// The OCRmyPDF executable path can be overridden here. Otherwise the default path will be used.
	// Special cases:
	// - "py -m ocrmypdf": This will run "py -m ocrmypdf".
	ExecutablePath string
}

// executableAndArgs returns the executable name and its base arguments.
func (c CLI) executableAndArgs() (string, []string) {
	// Get path of executable.
	execPath := ExecutablePath
	if c.ExecutablePath != "" {
		execPath = c.ExecutablePath
	}

	// Special cases.
	var args []string
	switch execPath {
	case "py -m ocrmypdf":
		execPath, args = "py", []string{"-m", "ocrmypdf"}
	}

	return execPath, args
}

// VersionString returns the version string as returned by OCRmyPDF.
func (c CLI) VersionString() (string, error) {
	execPath, args := c.executableAndArgs()

	args = append(args, "--version")

	cmd := exec.Command(execPath, args...)

	var output, errBuffer bytes.Buffer
	cmd.Stdout = &output
	cmd.Stderr = &errBuffer

	if err := cmd.Run(); err != nil {
		switch err := err.(type) {
		case *exec.ExitError:
			return "", fmt.Errorf("OCRmyPDF stopped with exit code %v: %v", err.ExitCode(), errBuffer.String())
		default:
			return "", err
		}
	}

	return strings.TrimRight(output.String(), "\n\r"), nil
}

// Run takes a document from input, and writes the resulting document into output.
// The options parameter is optional.
func (c CLI) Run(input io.Reader, output io.Writer, options *CLIOptions) error {
	execPath, args := c.executableAndArgs()

	if options != nil {
		args = append(args, options.Args()...)
	}

	args = append(args, "-", "-")

	cmd := exec.Command(execPath, args...)
	cmd.Stdin = input
	cmd.Stdout = output

	errBuffer := bytes.Buffer{}
	cmd.Stderr = &errBuffer

	if err := cmd.Run(); err != nil {
		switch err := err.(type) {
		case *exec.ExitError:
			return fmt.Errorf("OCRmyPDF stopped with exit code %v: %v", err.ExitCode(), errBuffer.String())
		default:
			return err
		}
	}

	return nil
}