package main // import "git.fromouter.space/mcg/htmlroc"
import (
	"flag"
	"fmt"
	"html/template"
	"io/ioutil"
	"os"
	"strings"
)

// Where are we in the file
const (
	FStart   = "start"    // File start
	InTOC    = "intoc"    // In Table of content
	AfterTOC = "aftertoc" // After Table of content
)

// TemplateData is the data that is filled and passed to the HTML template
type TemplateData struct {
	Title    string
	Credits  string
	Sections []*TemplateSection
}

// TemplateSection is a section of the rules
type TemplateSection struct {
	ID    string
	Title string
	Extra bool
	Rules []TemplateRule
	Text  string
}

// TemplateRule is a single rule
type TemplateRule struct {
	ID    string
	Text  string
	Depth int
}

var funmap = template.FuncMap{
	"toCredits": tplToCredits,
	"htmlify":   tplHtmlify,
}

// HTMLrocCredits is the credit string to append to the other credits
const HTMLrocCredits = "Converted to HTML using <a href=\"https://git.fromouter.space/mcg/htmlroc\">htmlroc</a>"

func main() {
	// Command line flags
	txtfile := flag.String("in", "rules.txt", "Path to rules.txt file")
	tplfile := flag.String("template", "template.html", "Path to template file")
	outname := flag.String("out", "out.html", "Output file")
	flag.Parse()

	// Read template file
	tpl, err := template.New(*tplfile).Funcs(funmap).ParseFiles(*tplfile)
	checkErr(err, "Could not load template file \"%s\"", *tplfile)

	tpldata := TemplateData{}

	// Read rules file
	filebytes, err := ioutil.ReadFile(*txtfile)
	checkErr(err, "Could not read rules file \"%s\"", *txtfile)

	filestr := string(filebytes)

	// Use table of content as delimiter between credits and rule text
	toc := strings.Index(filestr, "Table of Contents")
	if toc < 0 {
		fmt.Fprintln(os.Stderr, "could not find TOC")
		os.Exit(1)
	}

	// Extract credits
	tpldata.Credits, filestr = strings.TrimSpace(filestr[:toc]), filestr[toc:]

	// Add our own credits
	tpldata.Credits += "\n" + HTMLrocCredits

	// Rules are after TOC
	tocend := strings.Index(filestr, "\n\n")
	if tocend < 0 {
		fmt.Fprintln(os.Stderr, "could not find end of TOC")
		os.Exit(1)
	}

	// Strip TOC out
	filestr = filestr[tocend+2:]

	// Every rule is a line (pretty handy!)
	lines := strings.Split(filestr, "\n")
	var currentSection *TemplateSection
	for _, line := range lines {
		// Trim line (used for several purposes)
		trimmed := strings.TrimSpace(line)

		// Skip empty lines
		if len(trimmed) < 1 {
			continue
		}

		// All rules begin with "(ID)"
		isRule := trimmed[0] == '('

		// All sections begin with "N. "
		// for sake of not making this check extra complicated we're going to
		// assume it has to be within the first 5 characters
		isSection := strings.Index(trimmed[:5], ". ") > 0

		// Calculate depth based on number of whitespace (/2)
		depth := len(line) - len(trimmed)

		switch {
		// It's a section
		case isSection:
			parts := strings.SplitN(trimmed, ". ", 2)
			if len(parts) < 2 {
				// ???
				fmt.Fprintf(os.Stderr, "Found unexpected line: \"%s\"\n", trimmed)
				continue
			}
			// Create new section
			currentSection = &TemplateSection{
				ID:    parts[0],
				Title: parts[1],
				Rules: []TemplateRule{},
				Extra: false,
			}
			tpldata.Sections = append(tpldata.Sections, currentSection)

		// It's a new rule
		case isRule:

			// ID is between ()s
			endID := strings.IndexRune(trimmed, ')')
			if endID < 0 {
				// ???
				fmt.Fprintf(os.Stderr, "Found unexpected or malformed line: \"%s\"\n", trimmed)
				continue
			}

			currentSection.Rules = append(currentSection.Rules, TemplateRule{
				ID:    trimmed[1:endID],
				Text:  strings.TrimSpace(trimmed[endID+1:]),
				Depth: depth,
			})

		// It's something else
		default:
			// If there is at least a rule, assume it's a continuation of the last rule
			if len(currentSection.Rules) > 0 {
				currentSection.Rules[len(currentSection.Rules)-1].Text += "\n" + line
			} else {
				// No rules? Might be an extra
				currentSection.Extra = true
				currentSection.Text += line + "\n"
			}
		}
	}

	// Create output file
	outfile, err := os.Create(*outname)
	checkErr(err, "Could not create output file \"%s\"", *outname)
	defer outfile.Close()

	// Run template on output file stream
	checkErr(tpl.Execute(outfile, tpldata), "Error running template")
}

func checkErr(err error, fmtstr string, args ...interface{}) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "FATAL: "+fmtstr+":\n  ", args...)
		fmt.Fprintln(os.Stderr, err.Error())
		os.Exit(1)
	}
}

func tplToCredits(str string) template.HTML {
	// Make first line an heading
	idx := strings.IndexRune(str, '\n')
	if idx > 0 {
		str = "<h1>" + str[:idx] + "</h1><p>" + str[idx+1:]
	}
	// Wrap other lines in <p> tags
	str = strings.ReplaceAll(str, "\n", "</p><p>") + "</p>"
	return template.HTML(str)
}

func tplHtmlify(str string) template.HTML {
	// Replace newlines with <br />
	str = strings.ReplaceAll(str, "\n", "<br />")
	return template.HTML(str)
}