package main

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"math/rand"
	"regexp"
	"strconv"
	"strings"
	"time"
)

var (
	MetaKV          = regexp.MustCompile(`(\w+)::\s+(.*)`)
	niceDateParseRE = regexp.MustCompile(`^(\d{1,2})_([a-z]+)_(\d{4})$`)
	ParseFailed     = errors.New("parse failed")
	Months          = []string{
		"",
		"januari",
		"februari",
		"maart",
		"april",
		"mei",
		"juni",
		"juli",
		"augustus",
		"september",
		"oktober",
		"november",
		"december",
	}
)

type ParsedLink struct {
	ID       string `json:"ID"`
	Name     string `json:"title"`
	PageName string `json:"name"`
	Line     string `json:"line"`
	Href     string `json:"href"`
}

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

func RandStringBytes(n int) string {
	b := make([]byte, n)
	for i := range b {
		b[i] = letterBytes[rand.Intn(len(letterBytes))]
	}
	return string(b)
}

func ParseLinks(blockId string, content string) ([]ParsedLink, error) {
	hrefRE := regexp.MustCompile(`(#?\[\[\s*([^\]]+)\s*\]\])`)
	keywordsRE := regexp.MustCompile(`(\w+)::`)

	scanner := bufio.NewScanner(strings.NewReader(content))
	scanner.Split(bufio.ScanLines)

	var result []ParsedLink

	for scanner.Scan() {
		line := scanner.Text()

		links := hrefRE.FindAllStringSubmatch(line, -1)

		for _, matches := range links {
			link := matches[0]

			if link[0] == '#' {
				link = strings.TrimPrefix(link, "#[[")
			} else {
				link = strings.TrimPrefix(link, "[[")
			}

			link = strings.TrimSuffix(link, "]]")
			link = strings.TrimSpace(link)
			l := cleanNameURL(link)
			result = append(result, ParsedLink{blockId, link, l, line, ""})
		}

		keywords := keywordsRE.FindAllStringSubmatch(line, -1)
		for _, matches := range keywords {
			link := matches[1]
			l := cleanNameURL(link)
			result = append(result, ParsedLink{blockId, link, l, line, ""})
		}
	}

	return result, nil
}

func cleanNameURL(name string) string {
	return strings.Replace(name, " ", "_", -1)
}

func cleanTitle(name string) string {
	return strings.Replace(name, "_", " ", -1)
}

type stopwatch struct {
	start time.Time
	label string
}

func (sw *stopwatch) Start(label string) {
	sw.start = time.Now()
	sw.label = label
}

func (sw *stopwatch) Stop() {
	endTime := time.Now()
	d := endTime.Sub(sw.start)
	log.Printf("%-20s: %s\n", sw.label, d.String())
}

func todayPage() string {
	now := time.Now()
	return formatDatePageName(now)
}

func formatDateTitle(date time.Time) string {
	return fmt.Sprintf("%d %s %d", date.Day(), Months[date.Month()], date.Year())
}
func formatDatePageName(date time.Time) string {
	return fmt.Sprintf("%d_%s_%d", date.Day(), Months[date.Month()], date.Year())
}

func PageTitle(pageText string) (string, error) {
	var listItems []struct {
		Indented int
		Text     string
	}
	err := json.NewDecoder(strings.NewReader(pageText)).Decode(&listItems)
	if err != nil {
		return "", fmt.Errorf("while decoding page text: %w", err)
	}

	for _, li := range listItems {
		if matches := MetaKV.FindStringSubmatch(li.Text); matches != nil {
			if matches[1] == "Title" {
				return matches[2], nil
			}
		}
	}
	return "", fmt.Errorf("no meta title found in page text")
}

func parseMonth(month string) (time.Month, error) {
	for i, m := range Months {
		if m == month {
			return time.Month(i), nil
		}
	}
	return time.Month(0), fmt.Errorf("parseMonth: %q is not a recognized month", month)
}

func ParseDatePageName(name string) (time.Time, error) {
	if matches := niceDateParseRE.FindStringSubmatch(name); matches != nil {
		day, err := strconv.Atoi(matches[1])
		if err != nil {
			return time.Time{}, fmt.Errorf("%q: %s: %w", name, err, ParseFailed)
		}
		month, err := parseMonth(matches[2])
		if err != nil {
			return time.Time{}, fmt.Errorf("%q: %s: %w", name, err, ParseFailed)
		}
		year, err := strconv.Atoi(matches[3])
		if err != nil {
			return time.Time{}, fmt.Errorf("%q: %s: %w", name, err, ParseFailed)
		}
		return time.Date(year, month, day, 0, 0, 0, 0, time.Local), nil
	}
	return time.Time{}, fmt.Errorf("%q: invalid syntax: %w", name, ParseFailed)
}