ai-commit-msg

#!/usr/bin/env bash

# Exit if the `SKIP_AI_COMMIT_MSG_HOOK` environment variable is set
if [ -n "$GITAI_SKIP_AI_COMMIT_MSG_HOOK" ]; then
    exit 0
fi

# ANSI color codes for styling the output
RED='\033[0;31m'    # Sets text to red
GREEN='\033[0;32m'  # Sets text to green
YELLOW='\033[0;33m' # Sets text to yellow
BLUE='\033[0;34m'   # Sets text to blue
NC='\033[0m'        # Resets the text color to default, no color

DEFAULT_PROMPT_FILE=$HOME/.config/gitai/prompts/ai-commit-msg-prompt.txt

# Function to display help message
show_help() {
    cat <<EOF
Usage: $(basename "$0") [options]

Automatically generates a commit message for staged changes using an LLM.
This script is typically used as a 'prepare-commit-msg' Git hook.

Options:
  -h, --help    Display this help message and exit.

Environment Variables:
  GITAI_SKIP_AI_COMMIT_MSG_HOOK  If set to a non-empty value, the script will exit without generating a message.
  GITAI_MODEL                    Specifies the LLM model to use (e.g., 'gpt-4o'). Defaults to the model set as default in the 'llm' tool.
  GITAI_COMMIT_MSG_PROMPT        Path to a custom prompt file. Defaults to '$DEFAULT_PROMPT_FILE'.
  GITAI_LANG                     The language for the generated commit message. Defaults to 'English'.
EOF
}

# Function to display a spinning animation during the LLM processing
spin_animation() {
    local msg="$1"
    # Only show animation if output is going to a terminal
    if ! [ -t 1 ]; then
        echo "$1..." # Just show the message without animation
        return
    fi

    # Array of spinner characters for the animation
    local spinner=("⠋" "⠙" "⠹" "⠸" "⠼" "⠴" "⠦" "⠧" "⠇" "⠏")
    # Infinite loop to keep the animation running
    while true; do
        for i in "${spinner[@]}"; do
            tput civis                                    # Hide the cursor to enhance the animation appearance
            tput el1                                      # Clear the line from the cursor to the beginning to display the spinner
            printf "\r${YELLOW}%s${NC} %s..." "$i" "$msg" # Print the spinner and message
            sleep 0.1                                     # Delay to control the speed of the animation
            tput cub $((${#msg} + 5))                     # Move the cursor back to reset the spinner position
        done
    done
}

kill_spin() {
    if [ -n "$SPIN_PID" ]; then
        kill $SPIN_PID
        wait $SPIN_PID 2>/dev/null # Wait for the process to terminate and suppress error messages
        SPIN_PID=
        printf "\n"
    fi
}

# Function to handle interrupts
cleanup() {
    echo -e "\n${RED}Script interrupted. Cleaning up...${NC}"
    kill_spin
    tput cnorm # Show the cursor
    exit 1
}

init_config() {
    if [ ! -f "$DEFAULT_PROMPT_FILE" ]; then
        brew_prompt=$(brew --prefix)/share/gitai/prompts/ai-commit-msg-prompt.txt
        if [ ! -f "$brew_prompt" ]; then
            echo "Can't find a default configuration file. Please create one at $DEFAULT_PROMPT_FILE" >&2
            exit 1
        fi

        dir=$(dirname "$DEFAULT_PROMPT_FILE")
        mkdir -p "$dir"
        cp "$brew_prompt" "$DEFAULT_PROMPT_FILE"
    fi
}

init_config

trap cleanup SIGINT

# Parse command-line arguments for help flag
if [[ "$1" == "-h" || "$1" == "--help" ]]; then
    show_help
    exit 0
fi

# Check if the commit is a merge commit based on the presence of a second argument
if [ -n "$2" ]; then
    exit 0 # Exit script if it's a merge commit, no custom message needed
fi

# Check if the `llm` command is installed
if ! command -v llm &>/dev/null; then
    echo -e "${RED}Error: 'llm' command is not installed. Please install it and try again.${NC}"
    exit 1
fi

# The LLM command will use the model by the environment `MODEL`
MODEL=${GITAI_MODEL}
if [ -z "$MODEL" ]; then
    MODEL=$(llm models default)
fi
export LLM_MODEL="$MODEL"

PROMPT_FILE=${GITAI_COMMIT_MSG_PROMPT:-$DEFAULT_PROMPT_FILE}
LANGUAGE=${GITAI_LANG:-English}

if [ ! -f "$PROMPT_FILE" ]; then
    echo -e "${RED}Error: Prompt file not found: $PROMPT_FILE${NC}" >&2
    exit 1
fi
PROMPT_CONTENT="$(cat "$PROMPT_FILE")"
PROMPT=$(
    cat <<EOF
All non-code text responses must be written in the $LANGUAGE language indicated.

$PROMPT_CONTENT
EOF
)

diff=$(git diff --cached)
if [ -z "$diff" ]; then
    exit 0
fi

# Start the spinning animation in the background
spin_animation "Generating LLM commit message using $MODEL" &
SPIN_PID=$!

# Generate the commit message using `git diff` piped into `llm` command
# The LLM command takes a system prompt from a file as input
if ! commit_msg=$(echo "$diff" | llm -s "$PROMPT" 2>&1); then
    # Stop the spinning animation by killing its process
    kill_spin

    # Finalizing output
    tput cnorm  # Show the cursor again
    printf "\n" # Move the cursor to the next line

    printf "${RED}Error: 'llm' command failed to generate the commit message:\n${commit_msg}${NC}\n\nManually set the commit message"
    exit 1
fi

# Stop the spinning animation by killing its process
kill_spin

# Display the generated commit message with color-coded headings
# echo -e "${BLUE}=== Generated Commit Message ===${NC}"
# echo -e "${GREEN}$commit_msg${NC}"
# echo -e "${BLUE}=================================${NC}"
# echo

# Write the generated commit message to the specified file (usually the commit message file in .git)
TMP_FILE=$(mktemp)
if [ -z "$TMP_FILE" ]; then
    exit 1
fi
trap 'rm -f -- "$TMP_FILE"' EXIT

if ! {
    echo "$commit_msg"
    cat -- "$1"
} >"$TMP_FILE"; then
    echo "Error: Failed to stage new commit message, preserving original." >&2
    exit 1
fi
mv -- "$TMP_FILE" "$1"