#!/bin/sh
# Alpine Reproducible Build Script
# Builds packages with deterministic settings for fingerprint generation
#
# Usage: build.sh [build|diff] <package> <version> [patch_url...]
#
# Examples:
#   build.sh build openssl 3.0.7-r0
#   build.sh diff openssl 3.0.7-r0 3.0.8-r0
#   build.sh build openssl 3.0.7-r0 https://patch.url/CVE-2023-1234.patch

set -eu

COMMAND="${1:-help}"
PACKAGE="${2:-}"
VERSION="${3:-}"
OUTPUT_DIR="${OUTPUT_DIR:-/output}"

log() {
    echo "[$(date -u +%Y-%m-%dT%H:%M:%SZ)] $*" >&2
}

show_help() {
    cat <<EOF
Alpine Reproducible Builder

Usage:
    build.sh build <package> <version> [patch_urls...]
        Build a package with reproducible settings
    
    build.sh diff <package> <vuln_version> <patched_version>
        Build two versions and compute fingerprint diff
    
    build.sh --help
        Show this help message

Environment:
    SOURCE_DATE_EPOCH    Override timestamp (extracted from APKBUILD if not set)
    OUTPUT_DIR           Output directory (default: /output)
    CFLAGS              Additional compiler flags
    LDFLAGS             Additional linker flags

Examples:
    build.sh build openssl 3.0.7-r0
    build.sh build curl 8.1.0-r0 https://patch/CVE-2023-1234.patch
    build.sh diff openssl 3.0.7-r0 3.0.8-r0
EOF
}

setup_reproducible_env() {
    local pkg="$1"
    local ver="$2"
    
    # Extract SOURCE_DATE_EPOCH from APKBUILD if not set
    if [ -z "${SOURCE_DATE_EPOCH:-}" ]; then
        if [ -f "aports/main/$pkg/APKBUILD" ]; then
            # Use pkgrel date or fallback to current
            SOURCE_DATE_EPOCH=$(stat -c %Y "aports/main/$pkg/APKBUILD" 2>/dev/null || date +%s)
        else
            SOURCE_DATE_EPOCH=$(date +%s)
        fi
        export SOURCE_DATE_EPOCH
    fi
    
    log "SOURCE_DATE_EPOCH=$SOURCE_DATE_EPOCH"
    
    # Reproducible compiler flags
    export CFLAGS="${CFLAGS:-} -fno-record-gcc-switches -fdebug-prefix-map=$(pwd)=/build"
    export CXXFLAGS="${CXXFLAGS:-} ${CFLAGS}"
    export LDFLAGS="${LDFLAGS:-}"
    
    # Locale for deterministic sorting
    export LC_ALL=C.UTF-8
    export TZ=UTC
}

fetch_source() {
    local pkg="$1"
    local ver="$2"
    
    log "Fetching source for $pkg-$ver"
    
    # Clone aports if needed
    if [ ! -d "aports" ]; then
        git clone --depth 1 https://gitlab.alpinelinux.org/alpine/aports.git
    fi
    
    # Find package
    local pkg_dir=""
    for repo in main community testing; do
        if [ -d "aports/$repo/$pkg" ]; then
            pkg_dir="aports/$repo/$pkg"
            break
        fi
    done
    
    if [ -z "$pkg_dir" ]; then
        log "ERROR: Package $pkg not found in aports"
        return 1
    fi
    
    # Checkout specific version if needed
    cd "$pkg_dir"
    abuild fetch
    abuild unpack
}

apply_patches() {
    local src_dir="$1"
    shift
    
    for patch_url in "$@"; do
        log "Applying patch: $patch_url"
        curl -sSL "$patch_url" | patch -d "$src_dir" -p1
    done
}

build_package() {
    local pkg="$1"
    local ver="$2"
    shift 2
    local patches="$@"
    
    log "Building $pkg-$ver"
    
    setup_reproducible_env "$pkg" "$ver"
    
    cd /build
    fetch_source "$pkg" "$ver"
    
    if [ -n "$patches" ]; then
        apply_patches "src/$pkg-*" $patches
    fi
    
    # Build with reproducible settings
    abuild -r
    
    # Copy output
    local out_dir="$OUTPUT_DIR/$pkg-$ver"
    mkdir -p "$out_dir"
    cp -r ~/packages/*/*.apk "$out_dir/" 2>/dev/null || true
    
    # Extract binaries and fingerprints
    for apk in "$out_dir"/*.apk; do
        [ -f "$apk" ] || continue
        local apk_name=$(basename "$apk" .apk)
        mkdir -p "$out_dir/extracted/$apk_name"
        tar -xzf "$apk" -C "$out_dir/extracted/$apk_name"
        
        # Extract function fingerprints
        /usr/local/bin/extract-functions.sh "$out_dir/extracted/$apk_name" > "$out_dir/$apk_name.functions.json"
    done
    
    log "Build complete: $out_dir"
}

diff_versions() {
    local pkg="$1"
    local vuln_ver="$2"
    local patched_ver="$3"
    
    log "Building and diffing $pkg: $vuln_ver vs $patched_ver"
    
    # Build vulnerable version
    build_package "$pkg" "$vuln_ver"
    
    # Build patched version
    build_package "$pkg" "$patched_ver"
    
    # Compute diff
    local diff_out="$OUTPUT_DIR/$pkg-diff-$vuln_ver-vs-$patched_ver.json"
    
    # Simple diff of function fingerprints
    jq -s '
        .[0] as $vuln |
        .[1] as $patched |
        {
            package: "'"$pkg"'",
            vulnerable_version: "'"$vuln_ver"'",
            patched_version: "'"$patched_ver"'",
            vulnerable_functions: ($vuln | length),
            patched_functions: ($patched | length),
            added: [($patched[] | select(.name as $n | ($vuln | map(.name) | index($n)) == null))],
            removed: [($vuln[] | select(.name as $n | ($patched | map(.name) | index($n)) == null))],
            modified: [
                $vuln[] | .name as $n | .hash as $h |
                ($patched[] | select(.name == $n and .hash != $h)) |
                {name: $n, vuln_hash: $h, patched_hash: .hash}
            ]
        }
    ' \
        "$OUTPUT_DIR/$pkg-$vuln_ver"/*.functions.json \
        "$OUTPUT_DIR/$pkg-$patched_ver"/*.functions.json \
        > "$diff_out"
    
    log "Diff complete: $diff_out"
}

case "$COMMAND" in
    build)
        if [ -z "$PACKAGE" ] || [ -z "$VERSION" ]; then
            log "ERROR: Package and version required"
            show_help
            exit 1
        fi
        shift 2  # Remove command, package, version
        build_package "$PACKAGE" "$VERSION" "$@"
        ;;
    diff)
        PATCHED_VERSION="${4:-}"
        if [ -z "$PACKAGE" ] || [ -z "$VERSION" ] || [ -z "$PATCHED_VERSION" ]; then
            log "ERROR: Package, vulnerable version, and patched version required"
            show_help
            exit 1
        fi
        diff_versions "$PACKAGE" "$VERSION" "$PATCHED_VERSION"
        ;;
    --help|help)
        show_help
        ;;
    *)
        log "ERROR: Unknown command: $COMMAND"
        show_help
        exit 1
        ;;
esac