commit 47340aebb8a405b1d72f3b98d971fbd42d619aa5
Author: antanst <antanst@antanst.com>
Date:   Fri Feb 28 12:11:24 2025 +0200

    Initial commit

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0ba4b46
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,48 @@
+SHELL := /bin/env oksh
+export PATH := $(PATH)
+
+all: fmt lintfix tidy test clean build
+
+debug:
+	@echo "PATH: $(PATH)"
+	@echo "GOPATH: $(shell go env GOPATH)"
+	@which go
+	@which gofumpt
+	@which gci
+	@which golangci-lint
+
+clean:
+	rm -rf ./dist
+
+# Test
+test:
+	go test -race ./...
+
+tidy:
+	go mod tidy
+
+# Format code
+fmt:
+	gofumpt -l -w .
+	gci write .
+
+# Run linter
+lint: fmt
+	golangci-lint run
+
+# Run linter and fix
+lintfix: fmt
+	golangci-lint run --fix
+
+build: clean
+	mkdir ./dist
+	go build -race -o ./dist/gmi2html ./bin/gmi2html/gmi2html.go
+
+show-updates:
+	go list -m -u all
+
+update:
+	go get -u all
+
+update-patch:
+	go get -u=patch all
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..89b9cbd
--- /dev/null
+++ b/README.md
@@ -0,0 +1,15 @@
+# gmi2html
+
+A small library (and CLI tool) that converts Gemini text to HTML.
+
+To run tests and build:
+
+```shell
+make
+```
+
+Running:
+
+```shell
+./dist/gmi2html <gemtext.gmi >gemtext.html
+```
\ No newline at end of file
diff --git a/bin/gmi2html/gmi2html.go b/bin/gmi2html/gmi2html.go
new file mode 100644
index 0000000..d253967
--- /dev/null
+++ b/bin/gmi2html/gmi2html.go
@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/antanst/gmi2html"
+)
+
+func main() {
+	err := runApp()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+}
+
+func runApp() error {
+	data, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		return err
+	}
+
+	html := gmi2html.Gmi2html(string(data), "")
+	_, err = fmt.Fprintf(os.Stdout, "%s", html)
+	if err != nil {
+		return err
+	}
+	return nil
+}
diff --git a/gmi2html.go b/gmi2html.go
new file mode 100644
index 0000000..1e2de68
--- /dev/null
+++ b/gmi2html.go
@@ -0,0 +1,135 @@
+package gmi2html
+
+import (
+	"bytes"
+	"fmt"
+	"html/template"
+	"net/url"
+	"regexp"
+	"strings"
+)
+
+// Based on https://geminiprotocol.net/docs/gemtext-specification.gmi
+
+// Gmi2html converts Gemini text to HTML with proper escaping and wraps it in a container with typography-focused CSS
+func Gmi2html(text string, title string) string {
+	content := convertGeminiContent(text)
+
+	// Handle any template errors with container
+	var buffer bytes.Buffer
+	err := containerTmpl.Execute(&buffer, struct {
+		Title   string
+		Content template.HTML
+	}{
+		Title:   title,
+		Content: template.HTML(content), // Content already properly escaped in convertGeminiContent
+	})
+	if err != nil {
+		fmt.Printf("Error executing container template: %s\n", err)
+		return ""
+	}
+
+	return buffer.String()
+}
+
+// convertGeminiContent converts Gemini text to HTML with proper escaping
+func convertGeminiContent(text string) string {
+	lines := strings.Split(text, "\n")
+	var buffer bytes.Buffer
+	normalMode := true
+
+	for _, line := range lines {
+		switch {
+		case strings.HasPrefix(line, "=>"):
+			handleLinkLine(&buffer, line)
+		case strings.HasPrefix(line, "```"):
+			normalMode = !normalMode
+			// Don't output the ``` line
+		case strings.HasPrefix(line, "###"):
+			content := strings.TrimSpace(strings.TrimPrefix(line, "###"))
+			err := h3Tmpl.Execute(&buffer, content)
+			if err != nil {
+				return ""
+			}
+		case strings.HasPrefix(line, "##"):
+			content := strings.TrimSpace(strings.TrimPrefix(line, "##"))
+			err := h2Tmpl.Execute(&buffer, content)
+			if err != nil {
+				return ""
+			}
+		case strings.HasPrefix(line, "#"):
+			content := strings.TrimSpace(strings.TrimPrefix(line, "#"))
+			err := h1Tmpl.Execute(&buffer, content)
+			if err != nil {
+				return ""
+			}
+		case strings.HasPrefix(line, "*"):
+			content := strings.TrimSpace(strings.TrimPrefix(line, "*"))
+			err := listItemTmpl.Execute(&buffer, content)
+			if err != nil {
+				return ""
+			}
+		case strings.HasPrefix(line, ">"):
+			content := strings.TrimSpace(strings.TrimPrefix(line, ">"))
+			err := blockquoteTmpl.Execute(&buffer, content)
+			if err != nil {
+				return ""
+			}
+		default:
+			if normalMode {
+				err := textLineTmpl.Execute(&buffer, line)
+				if err != nil {
+					return ""
+				}
+			} else {
+				err := preformattedTmpl.Execute(&buffer, line)
+				if err != nil {
+					return ""
+				}
+			}
+		}
+	}
+
+	return buffer.String()
+}
+
+// handleLinkLine parses and renders a link line
+func handleLinkLine(buffer *bytes.Buffer, linkLine string) {
+	url, description, err := parseGeminiLink(linkLine)
+	if err != nil {
+		fmt.Printf("Error parsing gemini link line: %s\n", err)
+		return
+	}
+
+	err = linkTmpl.Execute(buffer, struct {
+		URL, Description string
+	}{url, description})
+	if err != nil {
+		return
+	}
+}
+
+// parseGeminiLink extracts URL and description from a link line
+func parseGeminiLink(linkLine string) (string, string, error) {
+	re := regexp.MustCompile(`^=>[ \t]+(\S+)([ \t]+.*)?`)
+	matches := re.FindStringSubmatch(linkLine)
+	if len(matches) == 0 {
+		return "", "", fmt.Errorf("error parsing link line: no regexp match for line %s", linkLine)
+	}
+
+	urlStr := matches[1]
+
+	// Check: Unescape the URL if escaped
+	_, err := url.QueryUnescape(urlStr)
+	if err != nil {
+		return "", "", fmt.Errorf("error parsing link line: %w input '%s'", err, linkLine)
+	}
+
+	// Set description to URL if not provided
+	description := urlStr
+	if len(matches) > 2 && strings.TrimSpace(matches[2]) != "" {
+		description = strings.TrimSpace(matches[2])
+	}
+
+	return urlStr, description, nil
+}
diff --git a/gmi2html_test.go b/gmi2html_test.go
new file mode 100644
index 0000000..bb82ffc
--- /dev/null
+++ b/gmi2html_test.go
@@ -0,0 +1,159 @@
+package gmi2html
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestConvertGeminiContent(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "Simple text line",
+			input:    "This is a simple text line",
+			expected: `<p class="gemini-textline">This is a simple text line</p>`,
+		},
+		{
+			name:     "Heading line level 1",
+			input:    "# Main heading",
+			expected: `<h1 class="gemini-heading-1">Main heading</h1>`,
+		},
+		{
+			name:     "Link line with description",
+			input:    "=> https://example.com Example site",
+			expected: `<div class="gemini-link-container"><a href="https://example.com">Example site</a></div>`,
+		},
+		{
+			name:     "List item",
+			input:    "* List item 1",
+			expected: `<p class="gemini-list-item">• List item 1</p>`,
+		},
+		{
+			name:     "Quote line",
+			input:    "> This is a quote",
+			expected: `<blockquote class="gemini-blockquote">This is a quote</blockquote>`,
+		},
+		{
+			name:     "Preformatted text",
+			input:    "```\ncode line 1\ncode line 2\n```",
+			expected: `<pre class="gemini-preformatted">code line 1</pre><pre class="gemini-preformatted">code line 2</pre>`,
+		},
+		{
+			name:     "Mixed content",
+			input:    "# Title\n\nNormal paragraph\n\n=> https://example.com Link to example",
+			expected: `<h1 class="gemini-heading-1">Title</h1><p class="gemini-textline"></p><p class="gemini-textline">Normal paragraph</p><p class="gemini-textline"></p><div class="gemini-link-container"><a href="https://example.com">Link to example</a></div>`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := convertGeminiContent(tt.input)
+			if result != tt.expected {
+				t.Errorf("convertGeminiContent(%q):\ngot:  %s\nwant: %s",
+					tt.input, result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestGmi2html(t *testing.T) {
+	sample := "# Hello Gemini\n\nThis is a test document.\n\n=> https://gemini.circumlunar.space/ Project Gemini"
+	result := Gmi2html(sample, "Gemini Test")
+
+	// Check that it contains the expected elements
+	if !strings.Contains(result, "<title>Gemini Test</title>") {
+		t.Error("Output HTML missing title")
+	}
+
+	if !strings.Contains(result, "<h1 class=\"gemini-heading-1\">Hello Gemini</h1>") {
+		t.Error("Output HTML missing properly formatted heading")
+	}
+
+	if !strings.Contains(result, "<a href=\"https://gemini.circumlunar.space/\">Project Gemini</a>") {
+		t.Error("Output HTML missing properly formatted link")
+	}
+
+	// Check that CSS is included
+	if !strings.Contains(result, "<style>") {
+		t.Error("Output HTML missing style section")
+	}
+
+	// Check that basic HTML structure is there
+	if !strings.Contains(result, "<!DOCTYPE html>") {
+		t.Error("Output HTML missing doctype declaration")
+	}
+
+	if !strings.Contains(result, "<div class=\"gemini-container\">") {
+		t.Error("Output HTML missing container div")
+	}
+}
+
+func TestParseGeminiLink(t *testing.T) {
+	tests := []struct {
+		name         string
+		input        string
+		expectedURL  string
+		expectedDesc string
+		expectError  bool
+	}{
+		{
+			name:         "Valid link with description",
+			input:        "=> https://example.com Example site",
+			expectedURL:  "https://example.com",
+			expectedDesc: "Example site",
+			expectError:  false,
+		},
+		{
+			name:         "Valid link without description",
+			input:        "=> https://example.com",
+			expectedURL:  "https://example.com",
+			expectedDesc: "https://example.com",
+			expectError:  false,
+		},
+		{
+			name:         "Link with special characters",
+			input:        "=> https://example.com/search?q=test Test search",
+			expectedURL:  "https://example.com/search?q=test",
+			expectedDesc: "Test search",
+			expectError:  false,
+		},
+		{
+			name:         "Malformed link line",
+			input:        "=>",
+			expectedURL:  "",
+			expectedDesc: "",
+			expectError:  true,
+		},
+		{
+			name:         "Link with multiple spaces in description",
+			input:        "=> https://example.com   Multiple    spaces",
+			expectedURL:  "https://example.com",
+			expectedDesc: "Multiple    spaces",
+			expectError:  false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			url, desc, err := parseGeminiLink(tt.input)
+
+			// Check error expectation
+			if (err != nil) != tt.expectError {
+				t.Errorf("Expected error: %v, got error: %v", tt.expectError, err != nil)
+			}
+
+			// If we expect success, check the result
+			if !tt.expectError {
+				if url != tt.expectedURL {
+					t.Errorf("Expected URL: %s, got: %s", tt.expectedURL, url)
+				}
+				if desc != tt.expectedDesc {
+					t.Errorf("Expected description: %s, got: %s", tt.expectedDesc, desc)
+				}
+			}
+		})
+	}
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..0a70863
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/antanst/gmi2html
+
+go 1.23.6
diff --git a/templates.go b/templates.go
new file mode 100644
index 0000000..84e9938
--- /dev/null
+++ b/templates.go
@@ -0,0 +1,143 @@
+package gmi2html
+
+import "html/template"
+
+// Templates for different line types
+
+var (
+	textLineTmpl     = template.Must(template.New("textLine").Parse(`<p class="gemini-textline">{{.}}</p>`))
+	h1Tmpl           = template.Must(template.New("h1").Parse(`<h1 class="gemini-heading-1">{{.}}</h1>`))
+	h2Tmpl           = template.Must(template.New("h2").Parse(`<h2 class="gemini-heading-2">{{.}}</h2>`))
+	h3Tmpl           = template.Must(template.New("h3").Parse(`<h3 class="gemini-heading-3">{{.}}</h3>`))
+	listItemTmpl     = template.Must(template.New("listItem").Parse(`<p class="gemini-list-item">• {{.}}</p>`))
+	blockquoteTmpl   = template.Must(template.New("blockquote").Parse(`<blockquote class="gemini-blockquote">{{.}}</blockquote>`))
+	preformattedTmpl = template.Must(template.New("preformatted").Parse(`<pre class="gemini-preformatted">{{.}}</pre>`))
+	linkTmpl         = template.Must(template.New("link").Parse(`<div class="gemini-link-container"><a href="{{.URL}}">{{.Description}}</a></div>`))
+
+	// Container template with typography-focused CSS
+	containerTmpl = template.Must(template.New("container").Parse(`<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>{{.Title}}</title>
+    <style>
+        :root {
+            --text-color: #333;
+            --bg-color: #fff;
+            --link-color: #0066cc;
+            --link-hover: #004080;
+            --quote-bg: #f5f5f5;
+            --quote-border: #ddd;
+            --pre-bg: #f8f8f8;
+            --pre-border: #eaeaea;
+        }
+        
+        @media (prefers-color-scheme: dark) {
+            :root {
+                --text-color: #eee;
+                --bg-color: #292929;
+                --link-color: #4a9eff;
+                --link-hover: #77b6ff;
+                --quote-bg: #333;
+                --quote-border: #444;
+                --pre-bg: #2a2a2a;
+                --pre-border: #3a3a3a;
+            }
+        }
+        
+body {
+    font-family: "Source Serif Pro", "Georgia", "Cambria", serif;
+    color: var(--text-color);
+    /* background-color: var(--bg-color); */
+    max-width: 34rem;
+    margin: 0 auto;
+    padding: 1rem 1rem;
+    font-size: 16px;
+    text-align: justify;
+    hyphens: auto;
+    -webkit-hyphens: auto;
+    -ms-hyphens: auto;
+}
+        
+        .gemini-container {
+            width: 100%;
+        }
+        
+        .gemini-heading-1 {
+            font-size: 2rem;
+            margin-top: 1rem;
+            margin-bottom: 1rem;
+            font-weight: 700;
+            line-height: 1.2;
+        }
+        
+        .gemini-heading-2 {
+            font-size: 1.6rem;
+            margin-top: 0.8rem;
+            margin-bottom: 0.8rem;
+            font-weight: 600;
+            line-height: 1.3;
+        }
+        
+        .gemini-heading-3 {
+            font-size: 1.3rem;
+            margin-top: 0.7rem;
+            margin-bottom: 0.7rem;
+            font-weight: 600;
+            line-height: 1.4;
+        }
+        
+        .gemini-textline {
+            margin-bottom: 1rem;
+        }
+        
+        .gemini-list-item {
+            margin: 0.5rem 0;
+            padding-left: 0.5rem;
+        }
+        
+        .gemini-link-container {
+            margin: 1rem 0;
+        }
+        
+        .gemini-link-container a {
+            color: var(--link-color);
+            text-decoration: none;
+            border-bottom: 1px solid transparent;
+            transition: border-color 0.2s ease;
+        }
+        
+        .gemini-link-container a:hover {
+            color: var(--link-hover);
+            border-bottom-color: var(--link-hover);
+        }
+        
+        .gemini-blockquote {
+            background-color: var(--quote-bg);
+            border-left: 3px solid var(--quote-border);
+            margin: 1.5rem 0;
+            padding: 0.8rem 1rem;
+            font-style: italic;
+        }
+        
+        .gemini-preformatted {
+            background-color: var(--pre-bg);
+            border: 1px solid var(--pre-border);
+            border-radius: 3px;
+            padding: 1rem;
+            overflow-x: auto;
+            font-family: monospace;
+            font-size: 0.9rem;
+            margin: 1rem 0;
+            white-space: pre-wrap;
+        }
+    </style>
+</head>
+<body>
+    <div class="gemini-container">
+        {{.Content}}
+    </div>
+</body>
+</html>`))
+)