package tequat

import (
    "bufio"
    "fmt"
    "html"
    "html/template"
    "mime"
    "net/http"
    "strings"

    "pkg.jfrech.com/brief/mailx"
    "pkg.jfrech.com/brief/tequat/internal/formathtml"
)

// TODO export when an HTML frontend is sincerely considered
func (tqa TQA) formatHTML(as *AttachmentStore, fields []mailx.Field, w http.ResponseWriter) error {
    w.Header().Set("Content-Type", "text/html; charset=utf-8")
    w.Header().Set("X-Content-Type-Options", "nosniff")

    var parts []template.HTML
    for _, atom := range []Atom(tqa) {
        switch a := atom.(type) {
        case Text:
            parts = append(parts, template.HTML(`<pre>` + html.EscapeString(a.Raw) + `</pre>`))
        case Quote:
            parts = append(parts, template.HTML(`<pre class="quote">` + html.EscapeString(addprefix(">", a.Raw)) + `</pre>`))
        case SignatureBlock:
            parts = append(parts, template.HTML(`<pre class="signature-block">-- ` + "\n" + html.EscapeString(a.Raw) + `</pre>`))

        case Attachment:
            asi, err := as.Put(a)
            if err != nil {
                return err
            }

            webviewableimage := func(t string) bool { return t == "image/png" || t == "image/jpeg" || t == "image/gif" } // TODO extend
            if t, _, err := mime.ParseMediaType(a.ContentType()); err == nil && webviewableimage(t) {
                parts = append(parts, template.HTML(`<img src="` + html.EscapeString("/attachment/" + string(asi)) + `">`))
            } else {
                parts = append(parts, template.HTML(`<pre>attached <a href="` + html.EscapeString("/attachment/" + string(asi)) + `">` + html.EscapeString(fmt.Sprintf("%s (%dB)", a.ContentType(), len(a.Data))) + `</a></pre>`))
            }

        // TODO case DroppedAlternatives:
        default:
            parts = append(parts, template.HTML(`<pre class="erroneous">` + html.EscapeString(fmt.Sprintf("unrecognised type: %T", a)) + `</pre>`))
        }
    }

    return formathtml.Templates.ExecuteTemplate(w, "mail.html", struct{
        Fields []mailx.Field;
        Parts []template.HTML;
    }{
        Fields: fields,
        Parts: parts,
    })
}

func addprefix(prefix string, lines string) string {
    b := new(strings.Builder)
    scanner := bufio.NewScanner(strings.NewReader(lines))
    for scanner.Scan() {
        b.WriteString(prefix)
        b.Write(scanner.Bytes())
        b.WriteString("\n")
    }
    if scanner.Err() != nil {
        panic("unreachable")
    }
    return b.String()
}