/* Parse typography.com, find typeface file names. */
/* Missing some styles. Use https://www.typography.com/api/v1/product_lines/100054?include=multipurpose_styles,office_styles,screen_smart_styles. */
package main

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/fs"
	"log"
	"net/http"
	"os"
	"regexp"
	"strconv"
	"strings"
)

const (
	base = "https://typography.com/api/v1"
)

func request(url string) []byte {
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		log.Fatal(err)
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		log.Fatal(err)
	}

	rt, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Fatal(err)
	}
	resp.Body.Close()

	return rt
}

func dlThenRead(name, url string) []byte {
	_, err := os.Stat(name)
	if errors.Is(err, fs.ErrNotExist) {
		log.Print(err)
		out, err := os.Create(name)
		if err != nil {
			log.Fatal(err)
		}
		defer out.Close()

		outWriter := bufio.NewWriter(out)
		_, err = outWriter.Write(request(url))
		if err != nil {
			log.Fatal(err)
		}
		_ = outWriter.Flush()
	} else if err != nil {
		log.Fatal(err)
	}

	in, err := os.Open(name)
	if err != nil {
		log.Fatal(err)
	}
	defer in.Close()

	inReader := bufio.NewReader(in)
	data, err := io.ReadAll(inReader)
	if err != nil {
		log.Fatal(err)
	}

	return data
}

func parseAndPrint(shortName, css string) {
	/* Grep for lines containing CSS rules with font names, */
	for _, line := range strings.Split(css, "\n") {
		match, err := regexp.Match("font-family:.*", []byte(line))
		if err != nil {
			log.Fatal(err)
		}
		if match {
			/* Remove rule boilerplate. */
			line = strings.Replace(line, "  font-family: ", "", 1)
			line = strings.Replace(line, ", Fallback, Courier;", "", 1)

			/* Split list of file names. */
			for _, style := range strings.Split(line, ", ") {
				/* TDB or TDA should become TD. Decided
				against the complexity of regexp for this. */
				style = strings.Replace(style, "TDB", "TD", 1)
				style = strings.Replace(style, "TDA", "TD", 1)

				/* Each style has two files: one with most
				of the glpyhs, another with just the ' '.
				Both are necessary, and need merging later. */
				fmt.Println(shortName, style)
				fmt.Println(shortName, style+"-Space")
			}
		}
	}
}

func traverse(name, shortName string, id string) {
	//fmt.Printf("%s %s %s\n", id, name, shortName)

	/* Create a directory for each typeface. The short name
	used in URLs contains no spaces. It works well for this use. */
	_, err := os.Stat(shortName)
	if err != nil {
		err = os.Mkdir(shortName, 0666)
		if err != nil {
			log.Fatal(err)
		}
	}
	err = os.Chdir(shortName)
	defer os.Chdir("..")

	/* The long name of the typeface is worth keeping. */
	_, err = os.Stat("name")
	if errors.Is(err, fs.ErrNotExist) {
		out, err := os.Create("name")
		if err != nil {
			log.Fatal(err)
		}
		defer out.Close()

		_, err = out.Write([]byte(name))
		if err != nil {
			log.Fatal(err)
		}
	}

	/* Using the ID passed in from the initial JSON, retrieve new
	JSON. This contains details on the actual typeface. */
	/* Parsing for OTF names in progress. */
	detailsJson := dlThenRead(id, base+"/product_lines/"+id+
		"?include=special_offers,multipurpose_styles,office_styles,screen_smart_styles&quantity=1&serializer=array")
	var details interface{}
	json.Unmarshal(detailsJson, &details)
	m := details.(map[string]interface{})

	/* The important field is an alphabetic identifier. It must be used
	in the following step. Hoop jumping. */
	alphaId := m["desktop_try_code"].(string)

	/* This JSON contains information about how the typeface
	should be layed out. Embedded is a set of CSS rules.
	The CSS rules contain the file names of each style of
	the typeface. */
	layoutJson := dlThenRead(alphaId, base+"/try/layout/"+
		alphaId)
	var layout interface{}
	json.Unmarshal(layoutJson, &layout)
	layoutMap := layout.(map[string]interface{})

	/* Interesting data is a few layers deep. */
	for _, mL2 := range layoutMap {
		for _, mL3 := range mL2.(map[string]interface{}) {
			switch mL3.(type) {
			case map[string]interface{}:
				mL4 := mL3.(map[string]interface{})
				layoutL2Json := []byte(mL4["layout_data"].(string))
				var layoutL2 interface{}
				json.Unmarshal(layoutL2Json, &layoutL2)

				/* Send the CSS for parsing. */
				parseAndPrint(shortName,
					layoutL2.(map[string]interface{})["css"].(string))
			case string:
			default:
			}
		}
	}

	/* OTF names. Base names are available as woff. */
	otf := m["multipurpose_styles"].(map[string]interface{})["styles"].([]interface{})
	for _, otf := range otf {
		style := otf.(map[string]interface{})["file_name"].(string)
		style = strings.TrimSuffix(style, ".otf")
		style = strings.Replace(style, "-SC", "-TD", 1)
		if !strings.Contains(style, "-TD") || strings.Contains(style,"_TD") ||
			shortName == "whitney" {
			continue
		}
		fmt.Println(shortName, style)
		fmt.Println(shortName, style+"-Space")
	}
}

func main() {
	/* findByName serves as the index to each of
	the typefaces. If it doesn't exist, download it. */
	_, err := os.Stat("findByName")
	if errors.Is(err, fs.ErrNotExist) {
		log.Print(err)
		out, err := os.Create("findByName")
		if err != nil {
			log.Fatal(err)
		}
		defer out.Close()

		outWriter := bufio.NewWriter(out)
		_, err = outWriter.Write(request(base +
			"/findByName?serializer=array"))
		if err != nil {
			log.Fatal(err)
		}
		_ = outWriter.Flush()
	}

	in, err := os.Open("findByName")
	if err != nil {
		log.Fatal(err)
	}
	defer in.Close()

	inReader := bufio.NewReader(in)
	indexJson, err := io.ReadAll(inReader)
	if err != nil {
		log.Fatal(err)
	}

	/* findByName is in JSON. */
	var index interface{}
	err = json.Unmarshal(indexJson, &index)
	if err != nil {
		log.Fatal(err)
	}

	/* The actually interesting data is a few levels deep. */
	m := index.(map[string]interface{})
	for _, mL2 := range m {
		for _, mL3 := range mL2.([]interface{}) {
			arr := mL3.(map[string]interface{})
			/* "name" is the full name, "slug" is the short name,
			"type_id" is the identifier used in the traversal. */
			traverse(arr["name"].(string),
				arr["slug"].(string),
				strconv.Itoa(int(arr["type_id"].(float64))))
		}
	}
}