package main

import (
	"errors"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"time"
)

const OCRMyPDFExecutable = "ocrmypdf"

type Runner struct {
	InputPatterns []string // The "Glob" patterns used for searching input files.
	OutputPath    string   // The output directory passed to OCRmyPDF.

	Interval time.Duration
}

func (r Runner) Run() {
	if r.Interval == 0 {
		r.Interval = 5 * time.Second
	}

	go func() {
		log.Printf("Starting runner polling %q every %s.", r.InputPatterns, r.Interval)

		ticker := time.NewTicker(r.Interval)
		for range ticker.C {

			for _, inputPattern := range r.InputPatterns {
				filenames, err := filepath.Glob(inputPattern)
				if err != nil {
					log.Panicf("Failed to get input files: %v.", err)
				}

				for _, filename := range filenames {

					base := filepath.Base(filename)
					outputPath := filepath.Join(r.OutputPath, base)

					log.Printf("Starting to process %q into %q.", base, outputPath)

					args := []string{
						"-l", "deu+eng",
						"--rotate-pages",
						"--optimize", "1",
						"--skip-text",
					}
					args = append(args, filename, outputPath)
					cmd := exec.Command(OCRMyPDFExecutable, args...)

					if output, err := cmd.CombinedOutput(); err != nil {
						log.Printf("OCRmyPDF stdout + stderr: %v.", string(output))
						var exitErr *exec.ExitError
						if errors.As(err, &exitErr) {
							log.Printf("OCRmyPDF failed with ExitCode: %v.", exitErr)
							log.Printf("We will move the document into the output directory instead.")
							if err := os.Rename(filename, outputPath); err != nil {
								log.Panicf("Failed to move %q to %q.", filename, outputPath)
							}
							log.Printf("Exec: %q", cmd)
						} else {
							log.Panicf("Failed to run OCRmyPDF: %v.", err)
						}
					} else {
						// Only delete the PDF if the previous steps did succeed.
						if err := os.Remove(filename); err != nil {
							log.Printf("Failed to remove original document: %v.", err)
						}
					}

					log.Printf("Finished processing of %q.", base)
				}
			}

		}
	}()
}