#!/bin/bash
# Detects local OS and maps to containerfiles target
# Returns target if found in buildtools/containerfiles/, empty string otherwise

set -euo pipefail

CONTAINERFILES_DIR="buildtools/containerfiles"

# Detect system architecture and map to containerfiles format
detect_arch() {
    local arch
    arch=$(uname -m)
    case "$arch" in
        x86_64)     echo "amd64" ;;
        aarch64)    echo "arm64" ;;
        armv7l)     echo "armhf" ;;
        i686|i386)  echo "i386" ;;
        riscv64)    echo "riscv64" ;;
        *)          echo "" ;;
    esac
}

# Detect distro and version from os-release
detect_distro() {
    local os_release="${1:-}"
    if [[ ! -r "$os_release" ]]; then
        return 1
    fi
    
    # Source the file safely - ID and VERSION_ID are environment variables
    . "$os_release"
    
    local distro="$ID"
    local version="$VERSION_ID"
    
    # Map distro ID to containerfiles naming convention
    case "$distro" in
        ubuntu|debian|fedora) ;;
        rocky|rhel|centos|almalinux) distro="rockylinux" ;;
        *)
            # Fallback to ID_LIKE for derivatives
            if [[ -n "${ID_LIKE:-}" ]]; then
                case "$ID_LIKE" in
                    *ubuntu*) distro="ubuntu" ;;
                    *debian*) distro="debian" ;;
                    *fedora*) distro="fedora" ;;
                esac
            fi
            ;;
    esac
    
    # Only return if we have valid distro and version
    if [[ -n "$distro" && -n "$version" ]]; then
        echo "$distro:$version"
    else
        return 1
    fi
}

# Try to find a matching containerfile target
find_containerfile() {
    local target="$1"
    local containerfile="${CONTAINERFILES_DIR}/${target}"
    
    # Direct match
    if [[ -d "$containerfile" || -f "$containerfile" ]]; then
        echo "$target"
        return 0
    fi
    
    return 1
}

# Main detection logic
main() {
    local arch
    
    # Detect architecture
    arch=$(detect_arch)
    if [[ -z "$arch" ]]; then
        echo "WARNING: Could not detect system architecture" >&2
        exit 1
    fi
    
    # Try to detect distro from multiple locations
    local distro_ver
    distro_ver=$(detect_distro "/etc/os-release") || \
    distro_ver=$(detect_distro "/usr/lib/os-release") || {
        echo "WARNING: Could not detect distro from os-release" >&2
        exit 1
    }
    
    # Build target string
    local target="${distro_ver}.${arch}"
    
    # Try to find matching containerfile
    if find_containerfile "$target"; then
        exit 0
    fi
    
    # Try with partial version matching (e.g., 25.10 → 25)
    local distro="${distro_ver%%:*}"
    local version="${distro_ver##*:}"
    
    # Strip last minor version number and try again
    local short_version="${version%.*}"
    if [[ -n "$short_version" ]]; then
        target="${distro}:${short_version}.${arch}"
        if find_containerfile "$target"; then
            exit 0
        fi
    fi
    
    # No match found
    echo "WARNING: No containerfile found for target: ${distro_ver}.${arch}" >&2
    exit 1
}

main "$@"