#!/usr/bin/env bash

#################################################################################
# This script is run by git before a commit is made.                            #
# To use it, copy it to .git/hooks/pre-commit and make it executable.           #
# Alternatively, run the following command from the root of the repo:           #
# git config core.hooksPath .githooks                                           #
#                                                                               #
#                                  FEATURES                                     #
# Updates the "updated" field in the front matter of .md files.                 #
# Compresses PNG files with either oxipng or optipng if available.              #
# Runs subset_font if config.toml has been modified.                            #
#                                                                               #
# Stops you from commiting:                                                     #
# - a draft .md file                                                            #
# - a file with a "TODO"                                                        #
# - a JS file without a minified version                                        #
# - a minified JS file that isn't as small as it can be                         #
# - a config.toml and theme.toml with different amounts of lines in [extra]     #
#################################################################################

# Function to exit the script with an error message.
function error_exit() {
    echo "ERROR: $1" >&2
    exit "${2:-1}"
}

# Function to extract the date from the front matter.
function extract_date() {
    local file="$1"
    local field="$2"
    grep -m 1 "^$field =" "$file" | sed -e "s/$field = //" -e 's/ *$//'
}

# Function to check if the .md file is a draft.
function is_draft() {
    local file="$1"
    awk '/^\+\+\+$/,/^\+\+\+$/ { if(/draft = true/) exit 0 } END { exit 1 }' "$file"
}

# Check if the file contains "TODO".
function contains_todo() {
    local file="$1"
    grep -q "TODO" "$file"
}

# Check for changes outside of the front matter.
function has_body_changes() {
    local file="$1"
    local in_front_matter=1
    local triple_plus_count=0

    diff_output=$(git diff --unified=999 --cached --output-indicator-new='%' --output-indicator-old='&' "$file")

    while read -r line; do
        if [[ "$line" =~ ^\+\+\+$ ]]; then
            triple_plus_count=$((triple_plus_count + 1))
            if [[ $triple_plus_count -eq 2 ]]; then
                in_front_matter=0
            fi
        elif [[ $in_front_matter -eq 0 ]]; then
            if [[ "$line" =~ ^[\%\&] ]]; then
                return 0
            fi
        fi
    done <<< "$diff_output"
    return 1
}

# Function to update the social media card for a post or section.
function generate_and_commit_card {
    local file=$1
    social_media_card=$(social-cards-zola -o static/img/social_cards -b http://127.0.0.1:1111 -u -p -i "$file") || {
        echo "Failed to update social media card for $file"
        exit 1
    }

    git add "$social_media_card" || {
        echo "Failed to add social media card $social_media_card"
        exit 1
    }

    git add "$file" || {
        echo "Failed to add $file"
        exit 1
    }
}

export -f generate_and_commit_card

function has_minified_version() {
    local file="$1"
    local extension="${file##*.}"
    local minified_file="${file%.*}.min.$extension"
    [ -f "$minified_file" ]
}

function is_minified() {
    local file="$1"

    # Check if terser and uglifyjs are installed.
    if ! command -v terser &> /dev/null || ! command -v uglifyjs &> /dev/null; then
        echo "Either terser or uglifyjs is not installed. Skipping minification check."
        return 0
    fi

    # Original file size.
    local original_size=$(wc -c < "$file")

    # File size after compression with terser.
    local terser_size=$(terser --compress --mangle -- "$file" | wc -c)

    # File size after compression with uglifyjs.
    local uglifyjs_size=$(uglifyjs --compress --mangle -- "$file" | wc -c)

    # Check if the file is already as small as or smaller than both minified versions.
    if (( original_size <= terser_size && original_size <= uglifyjs_size )); then
        return 0
    fi

    # If the file isn't as small as it can be, suggest the better compressor in the error message
    if (( terser_size < uglifyjs_size )); then
        error_exit "Minified JS file $file isn't as small as it can be! Try using terser for better compression."
    else
        error_exit "Minified JS file $file isn't as small as it can be! Try using uglifyjs for better compression."
    fi
}

# Check if the script is being run from the root of the repo.
if [[ ! $(git rev-parse --show-toplevel) == $(pwd) ]]; then
    error_exit "This script must be run from the root of the repo."
fi

# Check if oxipng is installed.
png_compressor=""
if command -v oxipng &> /dev/null; then
    png_compressor="oxipng -o max"
elif command -v optipng &> /dev/null; then
    png_compressor="optipng -o 7"
fi

##################################################################
# Compress PNG files with either oxipng or optipng if available. #
# Update the "updated" field in the front matter of .md files.   #
#          https://osc.garden/blog/zola-date-git-hook/           #
# Ensure the [extra] section from config.toml and theme.toml     #
# have the same amount of lines.                                 #
# Ensure JavaScript files are minified.                          #
##################################################################

# Get the newly added and modified files.
all_changed_files=$(git diff --cached --name-only --diff-filter=AM)

script_name=$(basename "$0")
# Loop through all newly added or modified files.
for file in $all_changed_files; do
    file_name=$(basename "$file")

    # Ignore this script and the changelog.
    if [[ "$file_name" == "$script_name" ]] || [[ "$file_name" == "CHANGELOG.md" ]]; then
        continue
    fi

    # If the file is a PNG and png_compressor is set, compress it and add it to the commit.
    if [[ "$file" == *.png ]] && [[ -n "$png_compressor" ]]; then
        $png_compressor "$file" || error_exit "Failed to compress PNG file $file"
        git add --force "$file" || error_exit "Failed to add compressed PNG file $file"
        continue
    fi

    # If the file contains "TODO", abort the commit.
    if contains_todo "$file"; then
        error_exit "File $file contains TODO! Remove or complete the TODO before committing."
    fi

    # If the file is a JS file and it doesn't have a minified version, abort the commit.
    if [[ "$file" == *.js ]] && [[ "$file" != *.min.js ]] && ! has_minified_version "$file"; then
        error_exit "JS file $file doesn't have a minified version!"
    fi

    # If the file is a minified JS file and it isn't as small as it can be, abort the commit.
    # Error message shows which minifier is best for the file.
    if [[ "$file" == *.min.js ]]; then
        is_minified "$file"
    fi

    # Ensure the [extra] section from config.toml and theme.toml have the same amount of lines.
    if [[ "$file" == "config.toml" ]] || [[ "$file" == "theme.toml" ]]; then
        # Get the line number where [extra] starts in config.toml.
        extra_line_config=$(grep -n "^\[extra\]$" "config.toml" | cut -d: -f1)

        # Get the line number where [extra] starts in theme.toml.
        extra_line_theme=$(grep -n "^\[extra\]$" "theme.toml" | cut -d: -f1)

        # Get the number of lines in the [extra] section in config.toml.
        extra_lines_config=$(tail -n +"$extra_line_config" "config.toml" | wc -l)

        # Get the number of lines in the [extra] section in theme.toml.
        extra_lines_theme=$(tail -n +"$extra_line_theme" "theme.toml" | wc -l)

        # Abort the commit if the number of lines in the [extra] section don't match.
        if [[ "$extra_lines_config" -ne "$extra_lines_theme" ]]; then
            error_exit "The [extra] section in config.toml and theme.toml don't have the same amount of lines!"
        fi
    fi
done

# Get the modified .md to update the "updated" field in the front matter.
modified_md_files=$(git diff --cached --name-only --diff-filter=M | grep -E '\.md$' | grep -v '_index.md$')

# Loop through each modified .md file.
for file in $modified_md_files; do
echo $file
    # If the file is an .md file and it's a draft, abort the commit.
    if is_draft "$file"; then
        error_exit "Draft file $file is being committed!"
    fi

    # If changes are only in the front matter, skip the file.
    if ! has_body_changes "$file"; then
        continue
    fi

    # Modify the "updated" date, if necessary.
    # Get the last modified date from the filesystem.
    last_modified_date=$(date -r "$file" +'%Y-%m-%d')

    # Extract the "date" field from the front matter.
    date_value=$(extract_date "$file" "date")

    # Skip the file if the last modified date is the same as the "date" field.
    if [[ "$last_modified_date" == "$date_value" ]]; then
        continue
    fi

    # Update the "updated" field with the last modified date.
    # If the "updated" field doesn't exist, create it below the "date" field.
    if ! awk -v date_line="$last_modified_date" 'BEGIN{FS=OFS=" = "; first = 1} {
        if (/^date =/ && first) {
            print; getline;
            if (!/^updated =/) print "updated" OFS date_line;
            first=0;
        }
        if (/^updated =/ && !first) gsub(/[^ ]*$/, date_line, $2);
        print;
    }' "$file" > "${file}.tmp"
    then
        error_exit "Failed to process $file with AWK"
    fi

    mv "${file}.tmp" "$file" || error_exit "Failed to overwrite $file with updated content"

    # Stage the changes.
    git add "$file"

done

# Use `social-cards-zola` to create/update the social media card for Markdown files.
# See https://osc.garden/blog/automating-social-media-cards-zola/ for context.
# Use parallel to create the social media cards in parallel and commit them.
# echo "$modified_md_files" | parallel -j 8 generate_and_commit_card

#########################################################
# Run subset_font if config.toml has been modified.     #
# https://welpo.github.io/tabi/blog/custom-font-subset/ #
#########################################################
if git diff --cached --name-only | grep -q "config.toml"; then
    echo "config.toml modified. Attempting to run subset_font…"

    # Check if subset_font is available and exit early if not.
    if ! command -v subset_font &> /dev/null; then
        echo "subset_font command not found. Skipping this step."
        exit 0
    fi

    # Call the subset_font script.
    ~/bin/subset_font -c config.toml -f static/fonts/Inter4.woff2 -o static/

    # Add the generated subset.css file to the commit.
    git add static/custom_subset.css
fi
