glowm - Glow wrapper with mermaid-ascii support for rendering diagrams in terminal

README.md

glowm

A wrapper for glow that renders mermaid diagrams as ASCII art using mermaid-ascii.

Installation

1. Install dependencies:

brew install glow
go install github.com/AlexanderGrooff/mermaid-ascii@latest

2. Download and make executable:

curl -o ~/.local/bin/glowm https://gist.githubusercontent.com/olavocarvalho/749053cb283642044064b93f183a056b/raw/glowm
chmod +x ~/.local/bin/glowm

Usage

glowm README.md
glowm -p README.md        # pager mode
cat README.md | glowm -   # stdin

glowm

#!/usr/bin/env bash
#
# glowm - Glow with Mermaid support
#
# Pre-processes markdown files to render ```mermaid blocks as ASCII
# before passing to glow for display.
#
# Requirements:
#   - glow (brew install glow)
#   - mermaid-ascii (go install github.com/AlexanderGrooff/mermaid-ascii@latest)
#
# Usage:
#   glowm README.md
#   glowm -p README.md        # pager mode
#   cat README.md | glowm -   # stdin
#

set -euo pipefail

# Check dependencies
check_deps() {
    local missing=()
    command -v glow >/dev/null 2>&1 || missing+=("glow")
    command -v mermaid-ascii >/dev/null 2>&1 || missing+=("mermaid-ascii")

    if [[ ${#missing[@]} -gt 0 ]]; then
        echo "Error: Missing dependencies: ${missing[*]}" >&2
        echo "Install with:" >&2
        [[ " ${missing[*]} " =~ " glow " ]] && echo "  brew install glow" >&2
        [[ " ${missing[*]} " =~ " mermaid-ascii " ]] && echo "  go install github.com/AlexanderGrooff/mermaid-ascii@latest" >&2
        exit 1
    fi
}

# Process markdown: replace ```mermaid blocks with ASCII rendered output
process_mermaid() {
    awk '
    BEGIN { in_mermaid = 0; mermaid_content = "" }

    /^```mermaid[[:space:]]*$/ {
        in_mermaid = 1
        mermaid_content = ""
        next
    }

    /^```[[:space:]]*$/ && in_mermaid {
        in_mermaid = 0

        # Write mermaid content to temp file and render
        cmd = "mktemp"
        cmd | getline tmpfile
        close(cmd)

        print mermaid_content > tmpfile
        close(tmpfile)

        # Render with mermaid-ascii
        render_cmd = "mermaid-ascii -f " tmpfile " 2>/dev/null"

        # Wrap output in a code block for nice glow rendering
        print "```"
        while ((render_cmd | getline line) > 0) {
            print line
        }
        close(render_cmd)
        print "```"

        # Cleanup
        system("rm -f " tmpfile)

        mermaid_content = ""
        next
    }

    in_mermaid {
        if (mermaid_content != "") mermaid_content = mermaid_content "\n"
        mermaid_content = mermaid_content $0
        next
    }

    { print }
    '
}

# Main
main() {
    check_deps

    local glow_args=()
    local input_file=""

    # Parse arguments
    while [[ $# -gt 0 ]]; do
        case "$1" in
            -)
                input_file="-"
                shift
                ;;
            -*)
                glow_args+=("$1")
                shift
                ;;
            *)
                input_file="$1"
                shift
                ;;
        esac
    done

    # Read input
    local content
    if [[ "$input_file" == "-" ]] || [[ -z "$input_file" ]]; then
        content=$(cat)
    elif [[ -f "$input_file" ]]; then
        content=$(cat "$input_file")
    else
        echo "Error: File not found: $input_file" >&2
        exit 1
    fi

    # Process and render
    echo "$content" | process_mermaid | glow "${glow_args[@]}" -
}

main "$@"