#!/bin/bash
# embed-frontend.sh — Convert built frontend assets into linkable object files.
#
# Usage: scripts/embed-frontend.sh <dist_dir> <output_dir>
#
# For each file in dist_dir, creates:
#   1. An object file via `ld -r -b binary` (raw bytes, zero bloat)
#   2. A generated embedded_assets.c with a lookup table
#
# Symbols created per file: _binary_<mangled_name>_start, _binary_<mangled_name>_end
# On macOS, these get a leading underscore: __binary_<mangled_name>_start

set -euo pipefail

DIST_DIR="${1:?Usage: embed-frontend.sh <dist_dir> <output_dir>}"
OUTPUT_DIR="${2:?Usage: embed-frontend.sh <dist_dir> <output_dir>}"

# Clean old embedded objects (asset hashes change on each build)
rm -rf "$OUTPUT_DIR"
mkdir -p "$OUTPUT_DIR"

# Detect platform — Linux uses ld -r -b binary, everything else uses xxd+cc
IS_LINUX=false
if [[ "$(uname -s)" == "Linux" ]] && ! [[ "$(uname -s)" =~ MINGW|MSYS ]]; then
    IS_LINUX=true
fi

# Content-type detection
content_type_for() {
    local f="$1"
    case "$f" in
        *.html) echo "text/html" ;;
        *.js)   echo "application/javascript" ;;
        *.css)  echo "text/css" ;;
        *.json) echo "application/json" ;;
        *.svg)  echo "image/svg+xml" ;;
        *.png)  echo "image/png" ;;
        *.ico)  echo "image/x-icon" ;;
        *.woff2) echo "font/woff2" ;;
        *.woff) echo "font/woff" ;;
        *.map)  echo "application/json" ;;
        *)      echo "application/octet-stream" ;;
    esac
}

# Mangle filename to valid C symbol: replace non-alnum with _
mangle() {
    echo "$1" | sed 's/[^a-zA-Z0-9]/_/g'
}

# Collect all files
FILES=()
while IFS= read -r -d '' file; do
    FILES+=("$file")
done < <(find "$DIST_DIR" -type f -print0 | sort -z)

if [[ ${#FILES[@]} -eq 0 ]]; then
    echo "Error: no files found in $DIST_DIR" >&2
    exit 1
fi

echo "Embedding ${#FILES[@]} files from $DIST_DIR"

# Generate object files
OBJ_FILES=()
for file in "${FILES[@]}"; do
    rel="${file#$DIST_DIR/}"
    mangled=$(mangle "$rel")
    obj="$OUTPUT_DIR/embed_${mangled}.o"

    if $IS_LINUX; then
        # Linux: ld -r -b binary (zero bloat, ELF only)
        abs_obj="$(cd "$(dirname "$0")/.." && pwd)/$obj"
        (cd "$DIST_DIR" && ld -r -b binary -o "$abs_obj" "$rel")
    else
        # macOS/Windows/MSYS2: generate C byte array + cc (no xxd dependency)
        local_c="$OUTPUT_DIR/embed_${mangled}.c"
        local_sym="_binary_${mangled}"

        echo "/* Generated from $rel */" > "$local_c"
        echo "const unsigned char ${local_sym}_data[] = {" >> "$local_c"
        # Use od (POSIX) to generate hex bytes — works everywhere without xxd/vim
        od -An -tx1 -v < "$file" | tr -s ' ' '\n' | grep -v '^$' | sed 's/^/0x/; s/$/,/' | paste -sd' ' - | fold -s -w 76 | sed 's/^/  /' >> "$local_c"
        echo "};" >> "$local_c"
        echo "const unsigned int ${local_sym}_size = sizeof(${local_sym}_data);" >> "$local_c"

        ${CC:-cc} -c -O2 -o "$obj" "$local_c"
        rm -f "$local_c"
    fi

    OBJ_FILES+=("$obj")
    echo "  $rel -> $obj"
done

# Generate embedded_assets.c
ASSETS_C="src/ui/embedded_assets.c"
cat > "$ASSETS_C" <<'HEADER'
/*
 * embedded_assets.c — Generated file mapping URL paths to embedded bytes.
 * DO NOT EDIT — regenerated by scripts/embed-frontend.sh
 */
#include "ui/embedded_assets.h"
#include <string.h>

HEADER

# Declare extern symbols
for file in "${FILES[@]}"; do
    rel="${file#$DIST_DIR/}"
    mangled=$(mangle "$rel")
    sym="_binary_${mangled}"

    if ! $IS_LINUX; then
        echo "extern const unsigned char ${sym}_data[];" >> "$ASSETS_C"
        echo "extern const unsigned int ${sym}_size;" >> "$ASSETS_C"
    else
        echo "extern const unsigned char ${sym}_start[];" >> "$ASSETS_C"
        echo "extern const unsigned char ${sym}_end[];" >> "$ASSETS_C"
    fi
done

echo "" >> "$ASSETS_C"
echo "cbm_embedded_file_t CBM_EMBEDDED_FILES[] = {" >> "$ASSETS_C"

for file in "${FILES[@]}"; do
    rel="${file#$DIST_DIR/}"
    mangled=$(mangle "$rel")
    sym="_binary_${mangled}"
    ct=$(content_type_for "$rel")

    # URL path: /index.html for root, /assets/... for assets
    url_path="/$rel"

    if ! $IS_LINUX; then
        echo "    {\"$url_path\", ${sym}_data, 0, \"$ct\"}," >> "$ASSETS_C"
    else
        echo "    {\"$url_path\", ${sym}_start, 0, \"$ct\"}," >> "$ASSETS_C"
    fi
done

echo "};" >> "$ASSETS_C"
echo "const int CBM_EMBEDDED_FILE_COUNT = ${#FILES[@]};" >> "$ASSETS_C"

# Generate size fixup
if $IS_LINUX; then
    # Linux: compute size from start/end pointers (ld -r -b binary symbols)
    cat >> "$ASSETS_C" <<'SIZEINIT'

static void __attribute__((constructor)) init_embedded_sizes(void) {
    cbm_embedded_file_t *files = CBM_EMBEDDED_FILES;
SIZEINIT

    for i in "${!FILES[@]}"; do
        rel="${FILES[$i]#$DIST_DIR/}"
        mangled=$(mangle "$rel")
        sym="_binary_${mangled}"
        echo "    files[$i].size = (unsigned int)(${sym}_end - ${sym}_start);" >> "$ASSETS_C"
    done

    echo "}" >> "$ASSETS_C"
else
    # macOS/Windows: use explicit _size vars from xxd-generated C arrays
    cat >> "$ASSETS_C" <<'SIZEINIT'

static void __attribute__((constructor)) init_embedded_sizes(void) {
    cbm_embedded_file_t *files = CBM_EMBEDDED_FILES;
SIZEINIT

    for i in "${!FILES[@]}"; do
        rel="${FILES[$i]#$DIST_DIR/}"
        mangled=$(mangle "$rel")
        sym="_binary_${mangled}"
        echo "    files[$i].size = ${sym}_size;" >> "$ASSETS_C"
    done

    echo "}" >> "$ASSETS_C"
fi

# Add lookup function
cat >> "$ASSETS_C" <<'LOOKUP'

const cbm_embedded_file_t *cbm_embedded_lookup(const char *path) {
    for (int i = 0; i < CBM_EMBEDDED_FILE_COUNT; i++) {
        if (strcmp(CBM_EMBEDDED_FILES[i].path, path) == 0) {
            return &CBM_EMBEDDED_FILES[i];
        }
    }
    return NULL;
}
LOOKUP

echo "Generated $ASSETS_C with ${#FILES[@]} embedded files"
echo "Object files in $OUTPUT_DIR:"
printf '  %s\n' "${OBJ_FILES[@]}"