#!/bin/bash
# RHEL Function Extraction Script
# Sprint: SPRINT_1227_0002_0001 (Reproducible Builders)
#
# Extracts function-level fingerprints from RPM packages

set -euo pipefail

RPM_PATH="${1:-}"
OUTPUT_DIR="${2:-/build/fingerprints}"

[[ -z "${RPM_PATH}" ]] && { echo "Usage: $0 <rpm_path> [output_dir]"; exit 1; }
[[ ! -f "${RPM_PATH}" ]] && { echo "RPM not found: ${RPM_PATH}"; exit 1; }

mkdir -p "${OUTPUT_DIR}"

RPM_NAME=$(rpm -qp --qf '%{NAME}' "${RPM_PATH}" 2>/dev/null)
RPM_VERSION=$(rpm -qp --qf '%{VERSION}-%{RELEASE}' "${RPM_PATH}" 2>/dev/null)

WORK_DIR=$(mktemp -d)
trap "rm -rf ${WORK_DIR}" EXIT

cd "${WORK_DIR}"

# Extract RPM contents
rpm2cpio "${RPM_PATH}" | cpio -idmv 2>/dev/null

# Find ELF binaries
find . -type f -exec file {} \; | grep -E 'ELF.*(executable|shared object)' | cut -d: -f1 | while read -r binary; do
    BINARY_NAME=$(basename "${binary}")
    BINARY_PATH="${binary#./}"
    
    # Get build-id if present
    BUILD_ID=$(readelf -n "${binary}" 2>/dev/null | grep 'Build ID:' | awk '{print $3}' || echo "")
    
    # Extract function symbols
    OUTPUT_FILE="${OUTPUT_DIR}/${RPM_NAME}_${BINARY_NAME}.json"
    
    {
        echo "{"
        echo "  \"package\": \"${RPM_NAME}\","
        echo "  \"version\": \"${RPM_VERSION}\","
        echo "  \"binary\": \"${BINARY_PATH}\","
        echo "  \"build_id\": \"${BUILD_ID}\","
        echo "  \"extracted_at\": \"$(date -u '+%Y-%m-%dT%H:%M:%SZ')\","
        echo "  \"functions\": ["
        
        # Extract function addresses and sizes using nm and objdump
        FIRST=true
        nm -S --defined-only "${binary}" 2>/dev/null | grep -E '^[0-9a-f]+ [0-9a-f]+ [Tt]' | while read -r addr size type name; do
            if [[ "${FIRST}" == "true" ]]; then
                FIRST=false
            else
                echo ","
            fi
            
            # Calculate function hash from disassembly
            FUNC_HASH=$(objdump -d --start-address=0x${addr} --stop-address=$((0x${addr} + 0x${size})) "${binary}" 2>/dev/null | \
                        grep -E '^\s+[0-9a-f]+:' | awk '{$1=""; print}' | sha256sum | cut -d' ' -f1)
            
            printf '    {"name": "%s", "address": "0x%s", "size": %d, "hash": "%s"}' \
                "${name}" "${addr}" "$((0x${size}))" "${FUNC_HASH}"
        done || true
        
        echo ""
        echo "  ]"
        echo "}"
    } > "${OUTPUT_FILE}"
    
    echo "Extracted: ${OUTPUT_FILE}"
done

echo "Function extraction complete for: ${RPM_NAME}"