/*******************************************************************************
* Copyright 2022 Stefan Majewsky <majewsky@gmx.net>
* SPDX-License-Identifier: GPL-3.0-only
* Refer to the file "LICENSE" for details.
*******************************************************************************/

package main

import (
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
)

type ScanResult struct {
	//episode date
	Day   int
	Month int
	Year  int
	//files discovered
	AudioFileNames []string
	//parts extracted from the shownotes
	Title       string
	AuthorNames string
	Description string
	//parts extracted from the chaptermarks
	ChapterMarks []ChapterMark
}

type ChapterMark struct {
	StartTime string
	Title     string
	URL       string
}

func Scan() (result ScanResult) {
	//determine episode date by finding shownotes file
	names, err := filepath.Glob("shownotes-pentaradio-*.txt")
	must(err)
	if len(names) == 0 {
		fail("no files found: shownotes-pentaradio-*.txt")
	}
	if len(names) > 1 {
		fail("multiple files found: shownotes-pentaradio-*.txt")
	}
	match := regexp.MustCompile(`^shownotes-pentaradio-(\d{4})-(\d{2})-(\d{2})\.txt$`).FindStringSubmatch(names[0])
	if match == nil {
		fail("cannot extract date from file name: %s", names[0])
	}

	//validate episode date
	result.Year, _ = strconv.Atoi(match[1])
	if result.Year < 2000 || result.Year > 2999 {
		fail("invalid year in filename: %s", names[0])
	}
	result.Month, _ = strconv.Atoi(match[2])
	if result.Month < 1 || result.Month > 12 {
		fail("invalid month in filename: %s", names[0])
	}
	result.Day, _ = strconv.Atoi(match[3])
	if result.Day < 1 || result.Day > 31 {
		fail("invalid day in filename: %s", names[0])
	}

	//parse input files
	result.ParseShownotes()
	result.ParseChapterMarks()

	//collect audio files
	pattern := fmt.Sprintf("pentaradio-%04d-%02d-%02d.*", result.Year, result.Month, result.Day)
	result.AudioFileNames, err = filepath.Glob(pattern)
	must(err)
	if len(names) == 0 {
		fail("no files found: %s", pattern)
	}

	return
}

var monthWords = []string{
	"Null",
	"Januar", "Februar", "März", "April",
	"Mai", "Juni", "Juli", "August",
	"September", "Oktober", "November", "Dezember",
}

func (scan ScanResult) ShowNotesFile() string {
	return fmt.Sprintf("shownotes-pentaradio-%04d-%02d-%02d.txt", scan.Year, scan.Month, scan.Day)
}

func (scan *ScanResult) ParseShownotes() {
	buf, err := os.ReadFile(scan.ShowNotesFile())
	must(err)

	expectedTitle := fmt.Sprintf("Pentaradio vom %d. %s %d", scan.Day, monthWords[scan.Month], scan.Year)
	shownotesRx := regexp.MustCompile(
		fmt.Sprintf(`^# %s\n`, expectedTitle) + //header line
			`# Titel: "(.*)"\n\n` + //episode title
			`Mit (.*)\.\n\n` + //author names
			`((?s:.*?))\n\n##\s`, //short description (everything up until the first <h2>)
	)
	match := shownotesRx.FindStringSubmatch(string(buf))
	if match == nil {
		fail("shownotes do not match expected format: /%s/", shownotesRx.String())
	}

	scan.Title = match[1]
	scan.AuthorNames = match[2]
	scan.Description = match[3]
}

func (scan ScanResult) ChapterMarksFile() string {
	return fmt.Sprintf("chapter-pentaradio-%04d-%02d-%02d.dat", scan.Year, scan.Month, scan.Day)
}

func (scan *ScanResult) ParseChapterMarks() {
	buf, err := os.ReadFile(scan.ChapterMarksFile())
	must(err)

	lineRx := regexp.MustCompile(`^(\d\d:\d\d:\d\d.\d\d\d) (\S.*?\S)(?: <(https?://.*)>)?$`)
	for _, line := range strings.Split(string(buf), "\n") {
		if strings.TrimSpace(line) == "" {
			continue
		}
		match := lineRx.FindStringSubmatch(line)
		if match == nil {
			fail("invalid format for chapter mark: %s", line)
		}
		scan.ChapterMarks = append(scan.ChapterMarks, ChapterMark{
			StartTime: match[1],
			Title:     match[2],
			URL:       match[3],
		})
	}
}