Add GeminiToHTML renderer

render.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"bufio"
+	"io"
+	"strings"
+)
+
+// GeminiToHTML reads Gemini from the provided reader and returns an HTML string.
+func GeminiToHTML(r io.Reader) string {
+	const spacetab = " \t"
+
+	type parseCtx int
+
+	const (
+		parseCtxNone = iota
+		parseCtxPre
+		parseCtxList
+	)
+
+	var builder strings.Builder
+	var ctx parseCtx
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if len(line) == 0 {
+			continue
+		}
+
+		if strings.HasPrefix(line, "```") {
+			if ctx != parseCtxPre {
+				builder.WriteString("<pre>\n")
+				ctx = parseCtxPre
+			} else {
+				builder.WriteString("</pre>\n")
+				ctx = parseCtxNone
+			}
+		} else if ctx == parseCtxPre {
+			builder.WriteString(line)
+			builder.WriteString("\n")
+		} else if strings.HasPrefix(line, "*") {
+			if ctx != parseCtxList {
+				builder.WriteString("<ul>\n")
+				ctx = parseCtxList
+			}
+			builder.WriteString("<li>")
+			line = line[1:]
+			builder.WriteString(strings.TrimLeft(line, spacetab))
+			builder.WriteString("</li>\n")
+		} else if ctx == parseCtxList {
+			builder.WriteString("</ul>\n")
+			ctx = parseCtxNone
+		} else if strings.HasPrefix(line, "###") {
+			line = line[3:]
+			line = strings.TrimLeft(line, spacetab)
+			builder.WriteString("<h3>" + line + "</h3>\n")
+		} else if strings.HasPrefix(line, "##") {
+			line = line[2:]
+			line = strings.TrimLeft(line, spacetab)
+			builder.WriteString("<h2>" + line + "</h2>\n")
+		} else if strings.HasPrefix(line, "#") {
+			line = line[1:]
+			line = strings.TrimLeft(line, spacetab)
+			builder.WriteString("<h1>" + line + "</h1>\n")
+		} else if strings.HasPrefix(line, "=>") {
+			line = line[2:]
+			line = strings.TrimLeft(line, spacetab)
+			split := strings.IndexAny(line, spacetab)
+			url := line[:split]
+			name := line[split:]
+			name = strings.TrimLeft(name, spacetab)
+			builder.WriteString("<p><a href='" + url + "'>" + name + "</a></p>\n")
+		} else if strings.HasPrefix(line, ">") {
+			builder.WriteString("<blockquote>" + line + "</blockquote>")
+		} else {
+			builder.WriteString("<p>" + line + "</p>\n")
+		}
+	}
+
+	// Close any opened tags
+	switch ctx {
+	case parseCtxPre:
+		builder.WriteString("</pre>\n")
+	case parseCtxList:
+		builder.WriteString("</ul>\n")
+	}
+	return builder.String()
+}