#!/bin/bash

# Simple Static Gallery Generator
# Generates a single-page gallery from images in the images/ directory

set -e

IMAGES_DIR="images"
OUTPUT_DIR="output"
TEMPLATES_DIR="templates"
ASSETS_DIR="assets"

# Load .env if present; see .env.example for every option and its default.
# Precedence: command line flags > environment > .env > built-in defaults.
ENV_FILE="${ENV_FILE:-.env}"
if [[ -f "$ENV_FILE" ]]; then
    # Remember caller-supplied values so the file cannot clobber them
    env_override=$(export -p | grep -E '^declare -x (STRIP_EXIF|GALLERY_TITLE|SHOW_FOOTER)=' || true)
    # shellcheck source=/dev/null
    source "$ENV_FILE"
    if [[ -n "$env_override" ]]; then
        eval "$env_override"
    fi
    unset env_override
fi

# Image metadata (EXIF/GPS/IPTC/XMP) is stripped by default.
# Opt out with STRIP_EXIF=0 or --keep-exif.
STRIP_EXIF="${STRIP_EXIF:-1}"

# Page title, used for both <title> and the <h1> header
GALLERY_TITLE="${GALLERY_TITLE:-Gallery}"

# Show the "Powered by shellery" footer; set to 0 to hide it
SHOW_FOOTER="${SHOW_FOOTER:-1}"

for arg in "$@"; do
    case "$arg" in
        --keep-exif) STRIP_EXIF=0 ;;
        --no-footer) SHOW_FOOTER=0 ;;
        --title=*)   GALLERY_TITLE="${arg#--title=}" ;;
        -h|--help)
            echo "usage: ./build.sh [--keep-exif] [--no-footer] [--title=TEXT]"
            echo "  --keep-exif    do not strip image metadata (env: STRIP_EXIF=0)"
            echo "  --no-footer    hide the 'Powered by shellery' footer (env: SHOW_FOOTER=0)"
            echo "  --title=TEXT   page title and header, default 'Gallery' (env: GALLERY_TITLE)"
            echo ""
            echo "Options may also be set in .env (see .env.example)."
            echo "Precedence: flags > environment > .env > defaults."
            exit 0 ;;
        *) echo "unknown option: $arg" >&2; exit 1 ;;
    esac
done

# Fail before writing any output if the default cannot be honoured
if [[ "$STRIP_EXIF" == "1" ]] && ! command -v exiftool >/dev/null 2>&1; then
    echo "error: exiftool is required to strip image metadata." >&2
    echo "  install: apt install libimage-exiftool-perl   (or: brew install exiftool)" >&2
    echo "  bypass:  STRIP_EXIF=0 ./build.sh   or   ./build.sh --keep-exif" >&2
    exit 1
fi

# Escape text destined for HTML body content
html_escape() {
    local s=$1
    # Replacements are quoted: bash 5.2+ expands an unquoted & to the matched text
    s="${s//&/"&amp;"}"
    s="${s//</"&lt;"}"
    s="${s//>/"&gt;"}"
    printf '%s' "$s"
}

TITLE_HTML=$(html_escape "$GALLERY_TITLE")

# Create output directory
mkdir -p "$OUTPUT_DIR"

# Start building the HTML file
OUTPUT_FILE="$OUTPUT_DIR/index.html"
> "$OUTPUT_FILE"

# Assemble templates in order
for template in $(ls "$TEMPLATES_DIR"/*.tmpl | sort); do
    skip_block=0
    # Process each template line by line to handle placeholders
    while IFS= read -r line; do
        # Optional block: <!-- IF_FOOTER --> ... <!-- ENDIF_FOOTER -->
        if [[ "$line" == *"<!-- IF_FOOTER -->"* ]]; then
            if [[ "$SHOW_FOOTER" != "1" ]]; then
                skip_block=1
            fi
            continue
        fi
        if [[ "$line" == *"<!-- ENDIF_FOOTER -->"* ]]; then
            skip_block=0
            continue
        fi
        if [[ "$skip_block" == "1" ]]; then
            continue
        fi

        # Replacement is quoted: bash 5.2+ expands an unquoted & to the matched text
        line="${line//<!-- TITLE -->/"$TITLE_HTML"}"

        if [[ "$line" == *"<!-- IMAGES -->"* ]]; then
            # Generate gallery items (reversed order)
            images=("$IMAGES_DIR"/*)
            for ((i=${#images[@]}-1; i>=0; i--)); do
                img="${images[$i]}"
                if [[ -f "$img" ]]; then
                    img_name=$(basename "$img")
                    echo "        <div class=\"gallery-item\">" >> "$OUTPUT_FILE"
                    echo "            <a href=\"#$img_name\">" >> "$OUTPUT_FILE"
                    echo "                <img src=\"images/$img_name\" alt=\"$img_name\" loading=\"lazy\">" >> "$OUTPUT_FILE"
                    echo "            </a>" >> "$OUTPUT_FILE"
                    echo "        </div>" >> "$OUTPUT_FILE"
                fi
            done
        elif [[ "$line" == *"<!-- LIGHTBOXES -->"* ]]; then
            # Generate lightboxes outside the gallery grid (reversed order)
            images=("$IMAGES_DIR"/*)
            for ((i=${#images[@]}-1; i>=0; i--)); do
                img="${images[$i]}"
                if [[ -f "$img" ]]; then
                    img_name=$(basename "$img")
                    echo "    <div id=\"$img_name\" class=\"lightbox\">" >> "$OUTPUT_FILE"
                    echo "        <a href=\"#\" class=\"lightbox-close\">&times;</a>" >> "$OUTPUT_FILE"
                    echo "        <img src=\"images/$img_name\" alt=\"$img_name\">" >> "$OUTPUT_FILE"
                    echo "    </div>" >> "$OUTPUT_FILE"
                fi
            done
        else
            echo "$line" >> "$OUTPUT_FILE"
        fi
    done < "$template"
done

# Copy assets
cp -r "$ASSETS_DIR"/* "$OUTPUT_DIR/"

# Copy images, then strip metadata from the copies (originals are never touched)
cp -r "$IMAGES_DIR" "$OUTPUT_DIR/"

if [[ "$STRIP_EXIF" == "1" ]]; then
    if compgen -G "$OUTPUT_DIR/$IMAGES_DIR/*" > /dev/null; then
        if ! exiftool -all= -overwrite_original -q -q "$OUTPUT_DIR/$IMAGES_DIR"; then
            echo "error: exiftool failed; output images may still contain metadata" >&2
            exit 1
        fi
    fi
else
    echo "warning: EXIF stripping disabled, image metadata will be published as-is" >&2
fi

echo "Gallery generated successfully in $OUTPUT_DIR/index.html"