import os
import ycm_core

# Set this to the absolute path to the folder (NOT the file!) containing the
# compile_commands.json file to use that instead of "flags". See here for
# more details: http://clang.llvm.org/docs/JSONCompilationDatabase.html
#
# Most projects will NOT need to set this to anything; you can just change the
# "flags" list of compilation flags. Notice that YCM itself uses that approach.
compilation_database_folder = ""

flags = [ "-Wall", "-Werror", "-std=c99" ]

if os.path.exists( compilation_database_folder ):
    database = ycm_core.CompilationDatabase( compilation_database_folder )
else:
    database = None

#SOURCE_EXTENSIONS = [ ".cpp", ".cxx", ".cc", ".c", ".m", ".mm" ]

def DirectoryOfThisScript():
  return os.path.dirname( os.path.abspath( __file__ ) )

def MakeRelativePathsInFlagsAbsolute( flags, working_directory ):
    if not working_directory:
        return list( flags )
    new_flags = []
    make_next_absolute = False
    path_flags = [ "-isystem", "-I", "-iquote", "--sysroot=" ]
    for flag in flags:
        new_flag = flag

    if make_next_absolute:
        make_next_absolute = False
        if not flag.startswith( "/" ):
            new_flag = os.path.join( working_directory, flag )

    for path_flag in path_flags:
        if flag == path_flag:
            make_next_absolute = True
            break

        if flag.startswith( path_flag ):
            path = flag[ len( path_flag ): ]
            new_flag = path_flag + os.path.join( working_directory, path )
            break

    if new_flag:
        new_flags.append( new_flag )
    return new_flags

def IsHeaderFile( filename ):
    extension = os.path.splitext( filename )[ 1 ]
    return extension in [ ".h", ".hxx", ".hpp", ".hh" ]

def GetCompilationInfoForFile( filename ):
    # The compilation_commands.json file generated by CMake does not have entries
    # for header files. So we do our best by asking the db for flags for a
    # corresponding source file, if any. If one exists, the flags for that file
    # should be good enough.
    if IsHeaderFile( filename ):
        basename = os.path.splitext( filename )[ 0 ]
        for extension in SOURCE_EXTENSIONS:
            replacement_file = basename + extension
            if os.path.exists( replacement_file ):
                compilation_info = database.GetCompilationInfoForFile(
                replacement_file )
            if compilation_info.compiler_flags_:
                return compilation_info
        return None
    return database.GetCompilationInfoForFile( filename )

def FlagsForFile( filename, **kwargs ):
    if database:
        # Bear in mind that compilation_info.compiler_flags_ does NOT return a
        # python list, but a "list-like" StringVec object
        compilation_info = GetCompilationInfoForFile( filename )
        if not compilation_info:
            return None

        final_flags = MakeRelativePathsInFlagsAbsolute(
                      compilation_info.compiler_flags_,
                      compilation_info.compiler_working_dir_ )

    else:
        relative_to = DirectoryOfThisScript()
        final_flags = MakeRelativePathsInFlagsAbsolute( flags, relative_to )

    return {
        "flags": final_flags,
        "do_cache": True
    }