package mdconv

import (
	"fmt"
	"io"
	"text/template"

	"tildegit.org/tjp/gus/gemtext"
)

func Convert(wr io.Writer, doc gemtext.Document, overrides *template.Template) error {
	tmpl, err := baseTmpl.Clone()
	if err != nil {
		return err
	}

	if overrides != nil {
		for _, override := range overrides.Templates() {
			tmpl, err = tmpl.AddParseTree(override.Name(), override.Tree)
			if err != nil {
				return err
			}
		}
	}

	return tmpl.ExecuteTemplate(wr, "mdconv", doc)
}

var baseTmpl = template.Must(template.New("mdconv").Parse(fmt.Sprintf((`
{{block "header" .}}{{end -}}
{{range . -}}
{{if .Type | eq %d}}{{block "textline" . -}}
	{{. -}}
{{end -}}
{{else if .Type | eq %d}}{{block "linkline" . -}}
	=> [{{if eq .Label ""}}{{.URL}}{{else}}{{.Label}}{{end}}]({{.URL}})
{{end -}}
{{else if .Type | eq %d}}{{block "preformattoggleline" . -}}
	` + "```" + `
{{end -}}
{{else if .Type | eq %d}}{{block "preformattedtextline" . -}}
	{{. -}}
{{end -}}
{{else if .Type | eq %d}}{{block "heading1line" . -}}
	# {{.Body}}
{{end -}}
{{else if .Type | eq %d}}{{block "heading2line" . -}}
	## {{.Body}}
{{end -}}
{{else if .Type | eq %d}}{{block "heading3line" . -}}
	### {{.Body}}
{{end -}}
{{else if .Type | eq %d}}{{block "listitemline" . -}}
	* {{.Body}}
{{end -}}
{{else if .Type | eq %d}}{{block "quoteline" . -}}
	> {{.Body}}
{{end -}}
{{end -}}
{{end -}}
{{block "footer" .}}{{end -}}
`)[1:],
	gemtext.LineTypeText,
	gemtext.LineTypeLink,
	gemtext.LineTypePreformatToggle,
	gemtext.LineTypePreformattedText,
	gemtext.LineTypeHeading1,
	gemtext.LineTypeHeading2,
	gemtext.LineTypeHeading3,
	gemtext.LineTypeListItem,
	gemtext.LineTypeQuote,
)))