#!/usr/bin/env bash

# compressJPG.sh: compress a JPG with mozjpeg if the savings are worthwhile.
# Author: Gwern Branwen
# Date: 2020-02-07
# When:  Time-stamp: "2026-05-08 17:33:15 gwern"
# License: CC-0

set -e

## Inlining for portability
# shellcheck source=./bash.sh
# . ~/wiki/static/build/bash.sh # for 'get_image_files', 'green', 'red'
red  () { echo -e "\e[41m$@\e[0m"; }
green () { echo -e "\e[32m$@\e[0m"; }
warn () { printf 'Warning: %s\n' "$*" >&2; }
SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
run_compressPNG () {
    if command -v compressPNG > /dev/null; then
        compressPNG "$@"
    elif [ -x "$SCRIPT_DIR/compressPNG" ]; then
        "$SCRIPT_DIR/compressPNG" "$@"
    else
        red "Error: compressPNG not found." >&2
        return 1
    fi
}
get_image_files () {
    mapfile -t "$1" < <(find . -maxdepth 1 -type f \
                             \( -iname "*.jpg" -o -iname "*.jpeg" \) \
                            | sort --version-sort)
}

args=("$@")
if [ ${#args[@]} -eq 0 ]; then
    get_image_files args
    green "Attempting to use implied arguments: ${args[@]}"
fi

if [ ${#args[@]} -eq 0 ]; then
    red "Error: no arguments available!"; exit 1
else
    command -v file > /dev/null
    for FILE in "${args[@]}"; do

        MIME_TYPE="$(file --brief --mime-type -- "$FILE" 2>/dev/null)" || {
            red "Error: unable to determine file type for $FILE" >&2
            continue
        }
        case "$MIME_TYPE" in
            image/png)
                red "compressJPG was called on PNG data in '$FILE'!"
                warn "Continuing by using 'compressPNG' without changing the extension…"
                run_compressPNG "$FILE"
                continue
                ;;
            image/jpeg)
                command -v jpegtran > /dev/null
                command -v mogrify > /dev/null
                ;;
            *)
                red "Error: $FILE is neither JPEG nor PNG data (file reports: $MIME_TYPE). Skipping." >&2
                continue
                ;;
        esac

        JPG_OLD="$(mktemp /tmp/XXXXXX-original.jpg)"
        TMP_NEW="$(mktemp /tmp/XXXXXX-temp.jpg)"
        cp "$FILE" "$JPG_OLD"
        jpegtran -copy none -progressive -optimize -outfile "$TMP_NEW" "$JPG_OLD"
        mogrify -quality 60 "$TMP_NEW"
        ORIGINAL=$(wc -c < "$JPG_OLD") # NOTE: '-c' instead of '--bytes' for portability
        SMALL=$(wc -c < "$TMP_NEW")
        RATIO=$(echo "$ORIGINAL / $SMALL" | bc --mathlib)
        echo "$FILE : from $ORIGINAL to $SMALL ($RATIO)"
        if (( $(echo "$RATIO > 1.2" | bc --mathlib) )); then
            mv "$TMP_NEW" "$FILE"
        else
            green "(Not updating $FILE because savings insufficient.)"
        fi
        rm --force "$JPG_OLD" "$TMP_NEW"
    done
fi