from waflib import Utils

def __run(cmd):
    try:
        cmd = Utils.subprocess.Popen(cmd,
                                     stdout=Utils.subprocess.PIPE,
                                     stderr=Utils.subprocess.PIPE,
                                     shell=True)
        output = cmd.stdout.read().strip()
        return output
    except Exception:
        return ""

def __add_swift_flags(ctx):
    ctx.env.SWIFT_FLAGS = ('-frontend -c -sdk %s -enable-objc-interop -emit-objc-header'
                           ' -emit-module -parse-as-library') % (ctx.env.MACOS_SDK)
    swift_version = __run(ctx.env.SWIFT +  ' -version').split(' ')[3].split('.')
    major, minor, sub = [int(n) for n in swift_version]

    # the -swift-version parameter is only supported on swift 3.1 and newer
    if major >= 3 and minor >= 1 or major >= 4:
        ctx.env.SWIFT_FLAGS += ' -swift-version 3'

    if ctx.is_optimization():
        ctx.env.SWIFT_FLAGS += ' -O'

def __add_swift_library_linking_flags(ctx, swift_library):
    ctx.env.append_value('LINKFLAGS', [
        '-L%s' % swift_library,
        '-Xlinker', '-force_load_swift_libs', '-lc++',
    ])

def __find_swift_library(ctx):
    swift_library_paths = [
        'Toolchains/XcodeDefault.xctoolchain/usr/lib/swift_static/macosx',
        'usr/lib/swift_static/macosx'
    ]
    dev_path = __run('xcode-select -p')[1:]

    ctx.start_msg('Checking for Swift Library')
    for path in swift_library_paths:
        swift_library = ctx.root.find_dir([dev_path, path])
        if swift_library is not None:
            ctx.end_msg(swift_library)
            __add_swift_library_linking_flags(ctx, swift_library)
            return
    ctx.end_msg(None, "RED")

def __find_macos_sdk(ctx):
    ctx.start_msg('Checking for macOS SDK')
    sdk = __run('xcrun --sdk macosx --show-sdk-path')
    if sdk != "":
        ctx.end_msg(sdk)
        ctx.env.MACOS_SDK = sdk
    else:
        ctx.end_msg(None, "RED")

def __find_swift_compiler(ctx):
    ctx.start_msg('Checking for swift (Swift compiler)')
    swift = __run('xcrun -find swift')
    if swift != "":
        ctx.end_msg(swift)
        ctx.env.SWIFT = swift
        __add_swift_flags(ctx)
        __find_swift_library(ctx)
    else:
        ctx.end_msg(None, "RED")

def configure(ctx):
    __find_macos_sdk(ctx)
    __find_swift_compiler(ctx)