'''
Support for accessing parse tree for MuPDF headers.
'''

import time

import jlib

from . import classes
from . import cpp
from . import state
from . import util

clang = state.clang


def get_extras(tu, type_):
    '''
    Returns (cursor, typename, extras):
        cursor: for base type.
        typename:
        extras: None or from classes.classextras.
    '''
    base_type = get_base_type( type_)
    base_type_cursor = base_type.get_declaration()
    base_typename = get_base_typename( base_type)
    extras = classes.classextras.get( tu, base_typename)
    return base_type_cursor, base_typename, extras


def prefix( name):
    if name.startswith( 'fz_'):
        return 'fz_'
    if name.startswith( 'pdf_'):
        return 'pdf_'
    assert 0, f'unrecognised prefix (not fz_ or pdf_) in name={name}'


def get_fz_extras( tu, fzname):
    '''
    Finds ClassExtra for <fzname>, coping if <fzname> starts with 'const ' or
    'struct '. Returns None if not found.
    '''
    fzname = util.clip( fzname, 'const ')
    fzname = util.clip( fzname, 'struct ')
    ce = classes.classextras.get( tu, fzname)
    return ce

def get_field0( type_):
    '''
    Returns cursor for first field in <type_> or None if <type_> has no fields.
    '''
    assert isinstance( type_, clang.cindex.Type)
    type_ = type_.get_canonical()
    for field in type_.get_fields():
        return field

get_base_type_cache = dict()
def get_base_type( type_):
    '''
    Repeatedly dereferences pointer and returns the ultimate type.
    '''
    # Caching reduces time from to 0.24s to 0.1s.
    key = type_.spelling
    ret = get_base_type_cache.get( key)
    if ret is None:
        while 1:
            type_ = type_.get_canonical()
            if type_.kind != clang.cindex.TypeKind.POINTER:
                break
            type_ = type_.get_pointee()
        ret = type_
        get_base_type_cache[ key] = ret

    return ret

def get_base_typename( type_):
    '''
    Follows pointer to get ultimate type, and returns its name, with any
    leading 'struct ' or 'const ' removed.
    '''
    type_ = get_base_type( type_)
    ret = type_.spelling
    ret = util.clip( ret, 'const ')
    ret = util.clip( ret, 'struct ')
    return ret

def is_double_pointer( type_):
    '''
    Returns true if <type_> is double pointer.
    '''
    type_ = type_.get_canonical()
    if type_.kind == clang.cindex.TypeKind.POINTER:
        type_ = type_.get_pointee().get_canonical()
        if type_.kind == clang.cindex.TypeKind.POINTER:
            return True

has_refs_cache = dict()
def has_refs( tu, type_):
    '''
    Returns (offset, bits) if <type_> has a 'refs' member, otherwise False.
        offset:
            Byte offset of 'refs' or name of 'refs' for use with offsetof(),
            e.g. 'super.refs'.
        bits:
            Size of 'refs' in bits.
    '''
    type0 = type_
    type_ = type_.get_canonical()

    key = type_.spelling
    key = util.clip(key, 'struct ')
    ret = has_refs_cache.get( key, None)
    if ret is None:
        ret = False
        #jlib.log( 'Analysing {type0.spelling=} {type_.spelling=} {key=}')

        for prefix in (
                'fz_',
                'pdf_',
                ):
            #jlib.log( '{type_.spelling=} {prefix=}')
            if key.startswith( prefix):
                #jlib.log( 'Type is a fz_ or pdf_ struct: {key=}')
                keep_name = f'{prefix}keep_{key[len(prefix):]}'
                keep_fn_cursor = state.state_.find_function( tu, keep_name, method=False)
                #jlib.log( '{keep_name=} {keep_fn_cursor=}')
                if keep_fn_cursor:
                    #jlib.log( 'There is a keep() fn for this type so it uses reference counting: {keep_name=}')
                    base_type_cursor = get_base_type( type_).get_declaration()
                    if base_type_cursor.is_definition():
                        #jlib.log( 'Type definition is available so we look for .refs member: {key=}')
                        for cursor in type_.get_fields():
                            name = cursor.spelling
                            type2 = cursor.type.get_canonical()
                            #jlib.log( '{name=} {type2.spelling=}')
                            if name == 'refs' and type2.spelling == 'int':
                                ret = 'refs', 32
                                break
                            if name == 'storable' and type2.spelling == 'struct fz_storable':
                                ret = 'storable.refs', 32
                                break
                    else:
                        #jlib.log('Definition is not available for {key=}')
                        pass

                    if not ret:
                        if 0:
                            jlib.log(
                                    'Cannot find .refs member or we only have forward'
                                    ' declaration, so have to hard-code the size and offset'
                                    ' of the refs member.'
                                    )
                        if base_type_cursor.is_definition():
                            if key == 'pdf_document':
                                ret = 'super.refs', 32
                            elif key == 'fz_pixmap':
                                ret = 'storable.refs', 32
                            elif key in (
                                    'fz_colorspace',
                                    'fz_image',
                                    ):
                                return 'key_storable.storable.refs', 32
                            elif key == 'pdf_cmap':
                                return 'storable.refs', 32
                        else:
                            #jlib.log( 'No defintion available, i.e. forward decl only.')
                            if key == 'pdf_obj':
                                ret = 0, 16
                            elif key == 'fz_path':
                                ret = 0, 8
                            elif key in (
                                    'fz_separations',
                                    'fz_halftone',
                                    'pdf_annot',
                                    'pdf_graft_map',
                                    ):
                                # Forward decl, first member is 'int regs;'.
                                return 0, 32
                            elif key in (
                                    'fz_display_list',
                                    'fz_glyph',
                                    'fz_jbig2_globals',
                                    'pdf_function',
                                    ):
                                # Forward decl, first member is 'fz_storable storable;'.
                                return 0, 32

                        if ret is None:
                            # Need to hard-code info for this type.
                            assert 0, jlib.expand_nv(
                                    '{key=} has {keep_name}() fn but is forward decl or we cannot find .regs,'
                                    ' and we have no hard-coded info about size and offset of .regs.'
                                    ' {type0.spelling=} {type_.spelling=} {base_type_cursor.spelling}'
                                    )
                    assert ret, f'{key} has {keep_name}() but have not found size/location of .refs member.'

        if type_.spelling in (
                'struct fz_document',
                'struct fz_buffer',
                ):
            assert ret
        #jlib.log('Populating has_refs_cache with {key=} {ret=}')
        has_refs_cache[ key] = ret
    return ret

def get_value( item, name):
    '''
    Enhanced wrapper for getattr().

    We call ourselves recursively if name contains one or more '.'. If name
    ends with (), makes fn call to get value.
    '''
    if not name:
        return item
    dot = name.find( '.')
    if dot >= 0:
        item_sub = get_value( item, name[:dot])
        return get_value( item_sub, name[dot+1:])
    if name.endswith('()'):
        value = getattr( item, name[:-2])
        assert callable(value)
        return value()
    return getattr( item, name)

def get_list( item, *names):
    '''
    Uses get_value() to find values of specified fields in <item>.

    Returns list of (name,value) pairs.
    '''
    ret = []
    for name in names:
        value = get_value( item, name)
        ret.append((name, value))
    return ret

def get_text( item, prefix, sep, *names):
    '''
    Returns text describing <names> elements of <item>.
    '''
    ret = []
    for name, value in get_list( item, *names):
        ret.append( f'{name}={value}')
    return prefix + sep.join( ret)

class Clang6FnArgsBug( Exception):
    def __init__( self, text):
        Exception.__init__( self, f'clang-6 unable to walk args for fn type. {text}')

def dump_ast( cursor, depth=0):
    indent = depth*4*' '
    for cursor2 in cursor.get_children():
        jlib.log( indent * ' ' + '{cursor2.kind=} {cursor2.mangled_name=} {cursor2.displayname=} {cursor2.spelling=}')
        dump_ast( cursor2, depth+1)


def show_ast( filename):
    index = clang.cindex.Index.create()
    tu = index.parse( filename,
            args=( '-I', clang_info().include_path),
            )
    dump_ast( tu.cursor)

class Arg:
    '''
    Information about a function argument.

        .cursor:
            Cursor for the argument.
        .name:
            Arg name, or an invented name if none was present.
        .separator:
            '' for first returned argument, ', ' for the rest.
        .alt:
            Cursor for underlying fz_ struct type if <arg> is a pointer to or
            ref/value of a fz_ struct type that we wrap. Else None.
        .out_param:
            True if this looks like an out-parameter, e.g. alt is set and
            double pointer, or arg is pointer other than to char.
        .name_python:
            Same as .name or .name+'_' if .name is a Python keyword.
        .name_csharp:
            Same as .name or .name+'_' if .name is a C# keyword.
    '''
    def __init__(self, cursor, name, separator, alt, out_param):
        self.cursor = cursor
        self.name = name
        self.separator = separator
        self.alt = alt
        self.out_param = out_param
        if name in ('in', 'is'):
            self.name_python = f'{name}_'
        else:
            self.name_python = name
        self.name_csharp = f'{name}_' if name in ('out', 'is', 'in', 'params') else name

    def __str__(self):
        return f'Arg(name={self.name} alt={"true" if self.alt else "false"} out_param={self.out_param})'


get_args_cache = dict()

def get_args( tu, cursor, include_fz_context=False, skip_first_alt=False, verbose=False):
    '''
    Yields Arg instance for each arg of the function at <cursor>.

    Args:
        tu:
            A clang.cindex.TranslationUnit instance.
        cursor:
            Clang cursor for the function.
        include_fz_context:
            If false, we skip args that are 'struct fz_context*'
        skip_first_alt:
            If true, we skip the first arg with .alt set.
        verbose:
            .
    '''
    # We are called a few times for each function, and the calculations we do
    # are slow, so we cache the returned items. E.g. this reduces total time of
    # --build 0 from 3.5s to 2.1s.
    #
    key = tu, cursor.location.file, cursor.location.line, include_fz_context, skip_first_alt
    ret = get_args_cache.get( key)
    if not verbose and state.state_.show_details(cursor.spelling):
        verbose = True
        #jlib.log('Verbose because {cursor.spelling=}')
    if ret is None:
        ret = []
        i = 0
        i_alt = 0
        separator = ''
        for arg_cursor in cursor.get_arguments():
            assert arg_cursor.kind == clang.cindex.CursorKind.PARM_DECL
            if not include_fz_context and is_pointer_to( arg_cursor.type, 'fz_context'):
                # Omit this arg because our generated mupdf_*() wrapping functions
                # use internalContextGet() to get a context.
                continue
            name = arg_cursor.mangled_name or f'arg_{i}'
            if 0 and name == 'stmofsp':
                verbose = True
            alt = None
            out_param = False
            base_type_cursor, base_typename, extras = get_extras( tu, arg_cursor.type)
            if verbose:
                jlib.log( 'Looking at arg. {extras=}')
            if extras:
                if verbose:
                    jlib.log( '{extras.opaque=} {base_type_cursor.kind=} {base_type_cursor.is_definition()=}')
                if extras.opaque:
                    # E.g. we don't have access to defintion of fz_separation,
                    # but it is marked in classes.classextras with opaque=true,
                    # so there will be a wrapper class.
                    alt = base_type_cursor
                elif (1
                        and base_type_cursor.kind == clang.cindex.CursorKind.STRUCT_DECL
                        #and base_type_cursor.is_definition()
                        ):
                    alt = base_type_cursor
            if verbose:
                jlib.log( '{arg_cursor.type.spelling=} {base_typename=} {arg_cursor.type.kind=} {get_base_typename(arg_cursor.type)=}')
            if alt:
                if is_double_pointer( arg_cursor.type):
                    out_param = True
            elif get_base_typename( arg_cursor.type) in ('char', 'unsigned char', 'signed char', 'void', 'FILE'):
                if is_double_pointer( arg_cursor.type):
                    if verbose:
                        jlib.log( 'setting outparam: {cursor.spelling=} {arg_cursor.type=}')
                    if cursor.spelling == 'pdf_clean_file':
                        # Don't mark char** argv as out-param, which will also
                        # allow us to tell swig to convert python lists into
                        # (argc,char**) pair.
                        pass
                    else:
                        if verbose:
                            jlib.log('setting out_param to true')
                        out_param = True
            elif base_typename.startswith( ('fz_', 'pdf_')):
                # Pointer to fz_ struct is not usually an out-param.
                if verbose: jlib.log( 'not out-param because arg is: {arg_cursor.displayname=} {base_type.spelling=} {extras}')
            elif arg_cursor.type.kind == clang.cindex.TypeKind.POINTER:
                pointee = arg_cursor.type.get_pointee()
                if verbose:
                    jlib.log( 'clang.cindex.TypeKind.POINTER')
                if pointee.get_canonical().kind == clang.cindex.TypeKind.FUNCTIONPROTO:
                    # Don't mark function-pointer args as out-params.
                    if verbose:
                        jlib.log( 'clang.cindex.TypeKind.FUNCTIONPROTO')
                elif pointee.is_const_qualified():
                    if verbose:
                        jlib.log( 'is_const_qualified()')
                elif pointee.spelling == 'FILE':
                    pass
                else:
                    if verbose:
                        jlib.log( 'setting out_param = True')
                    out_param = True
            if alt:
                i_alt += 1
            i += 1
            if alt and skip_first_alt and i_alt == 1:
                continue
            arg =  Arg(arg_cursor, name, separator, alt, out_param)
            ret.append(arg)
            if verbose:
                jlib.log( 'Appending {arg=}')
            separator = ', '

        get_args_cache[ key] = ret

    for arg in ret:
        yield arg


def fn_has_struct_args( tu, cursor):
    '''
    Returns true if fn at <cursor> takes any fz_* struct args.
    '''
    for arg in get_args( tu, cursor):
        if arg.alt:
            return True

def get_first_arg( tu, cursor):
    '''
    Returns (arg, n), where <arg> is from get_args() for first argument (or
    None if no arguments), and <n> is number of arguments.
    '''
    n = 0
    ret = None
    for arg in get_args( tu, cursor):
        if n == 0:
            ret = arg
        n += 1
    return ret, n


is_pointer_to_cache = dict()

def is_pointer_to( type_, destination, verbose=False):
    '''
    Returns true if <type> is a pointer to <destination>.

    We do this using text for <destination>, rather than a clang.cindex.Type
    or clang.cindex.Cursor, so that we can represent base types such as int or
    char without having clang parse system headers. This involves stripping any
    initial 'struct ' text.

    Also, clang's representation of mupdf's varying use of typedef, struct and
    forward-declarations is rather difficult to work with directly.

    type_:
        A clang.cindex.Type.
    destination:
        Text typename.
    '''
    # Use cache - reduces time from 0.6s to 0.2.
    #
    key = type_.spelling, destination
    ret = is_pointer_to_cache.get( key)
    if ret is None:
        assert isinstance( type_, clang.cindex.Type)
        ret = None
        destination = util.clip( destination, 'struct ')
        if verbose:
            jlib.log('{type_.kind=}')
        if type_.kind == clang.cindex.TypeKind.POINTER:
            pointee = type_.get_pointee().get_canonical()
            d = cpp.declaration_text( pointee, '')
            d = util.clip( d, 'const ')
            d = util.clip( d, 'struct ')
            if verbose:
                jlib.log( '{destination!r=} {d!r=}')
            ret = d == f'{destination} ' or d == f'const {destination} '
        is_pointer_to_cache[ key] = ret

    return ret

def is_pointer_to_pointer_to( type_, destination):
    if type_.kind != clang.cindex.TypeKind.POINTER:
        return False
    return is_pointer_to( type_.get_pointee().get_canonical(), destination)


class MethodExcludeReason_VARIADIC:
    pass
class MethodExcludeReason_OMIT_CLASS:
    pass
class MethodExcludeReason_NO_EXTRAS:
    pass
class MethodExcludeReason_NO_RAW_CONSTRUCTOR:
    pass
class MethodExcludeReason_NOT_COPYABLE:
    pass
class MethodExcludeReason_NO_WRAPPER_CLASS:
    pass
class MethodExcludeReason_ENUM:
    pass
class MethodExcludeReason_FIRST_ARG_NOT_STRUCT:
    pass

# Maps from <structname> to list of functions satisfying conditions specified
# by find_wrappable_function_with_arg0_type() below.
#
find_wrappable_function_with_arg0_type_cache = None

# Maps from fnname to list of strings, each string being a description of why
# this fn is not suitable for wrapping by class method.
#
find_wrappable_function_with_arg0_type_excluded_cache = None

def find_wrappable_function_with_arg0_type_cache_populate( tu):
    '''
    Populates caches with wrappable functions.
    '''
    global find_wrappable_function_with_arg0_type_cache
    global find_wrappable_function_with_arg0_type_excluded_cache

    if find_wrappable_function_with_arg0_type_cache:
        return

    t0 = time.time()

    find_wrappable_function_with_arg0_type_cache = dict()
    find_wrappable_function_with_arg0_type_excluded_cache = dict()

    for fnname, cursor in state.state_.find_functions_starting_with( tu, ('fz_', 'pdf_'), method=True):

        exclude_reasons = []

        if fnname.startswith( 'fz_drop_') or fnname.startswith( 'fz_keep_'):
            continue
        if fnname.startswith( 'pdf_drop_') or fnname.startswith( 'pdf_keep_'):
            continue

        if cursor.type.is_function_variadic():
            exclude_reasons.append(
                    (
                    MethodExcludeReason_VARIADIC,
                    'function is variadic',
                    ))

        # Look at resulttype.
        #
        result_type = cursor.type.get_result().get_canonical()
        if result_type.kind == clang.cindex.TypeKind.POINTER:
            result_type = result_type.get_pointee().get_canonical()
        result_type = util.clip( result_type.spelling, 'struct ')
        if result_type.startswith( ('fz_', 'pdf_')):
            result_type_extras = get_fz_extras( tu, result_type)
            if not result_type_extras:
                exclude_reasons.append(
                        (
                        MethodExcludeReason_NO_EXTRAS,
                        f'no extras defined for result_type={result_type}',
                        ))
            else:
                if not result_type_extras.constructor_raw:
                    exclude_reasons.append(
                            (
                            MethodExcludeReason_NO_RAW_CONSTRUCTOR,
                            f'wrapper for result_type={result_type} does not have raw constructor.',
                            ))
                if not result_type_extras.copyable:
                    exclude_reasons.append(
                            (
                            MethodExcludeReason_NOT_COPYABLE,
                                f'wrapper for result_type={result_type} is not copyable.',
                            ))

        # Look at args
        #
        i = 0
        arg0_cursor = None
        for arg in get_args( tu, cursor):

            base_typename = get_base_typename( arg.cursor.type)
            if not arg.alt and base_typename.startswith( ('fz_', 'pdf_')):
                if arg.cursor.type.get_canonical().kind == clang.cindex.TypeKind.ENUM:
                    # We don't (yet) wrap fz_* enums, but for now at least we
                    # still wrap functions that take fz_* enum parameters -
                    # callers will have to use the fz_* type.
                    #
                    # For example this is required by mutool_draw.py because
                    # mudraw.c calls fz_set_separation_behavior().
                    #
                    jlib.logx( 'not excluding {fnname=} with enum fz_ param : {arg.cursor.spelling=} {arg.cursor.type.kind} {arg.cursor.type.get_canonical().kind=}')
                else:
                    exclude_reasons.append(
                            (
                            MethodExcludeReason_NO_WRAPPER_CLASS,
                            f'no wrapper class for arg i={i}: {arg.cursor.type.get_canonical().spelling} {arg.cursor.type.get_canonical().kind}',
                            ))
            if i == 0:
                if arg.alt:
                    arg0_cursor = arg.alt
                else:
                    exclude_reasons.append(
                            (
                            MethodExcludeReason_FIRST_ARG_NOT_STRUCT,
                            'first arg is not fz_* struct',
                            ))
            i += 1

        if exclude_reasons:
            find_wrappable_function_with_arg0_type_excluded_cache[ fnname] = exclude_reasons
            #if fnname == 'fz_load_outline':   # lgtm [py/unreachable-statement]
            if state.state_.show_details(fnname):
                jlib.log( 'Excluding {fnname=} from possible class methods because:')
                for i in exclude_reasons:
                    jlib.log( '    {i}')
        else:
            if i > 0:
                # <fnname> is ok to wrap.
                arg0 = arg0_cursor.type.get_canonical().spelling
                arg0 = util.clip( arg0, 'struct ')

                items = find_wrappable_function_with_arg0_type_cache.setdefault( arg0, [])
                items.append( fnname)

    jlib.logx( f'populating find_wrappable_function_with_arg0_type_cache took {time.time()-t0}s')


def find_wrappable_function_with_arg0_type( tu, structname):
    '''
    Return list of fz_*() function names which could be wrapped as a method of
    our wrapper class for <structname>.

    The functions whose names we return, satisfy all of the following:

        First non-context param is <structname> (by reference, pointer or value).

        If return type is a fz_* struc (by reference, pointer or value), the
        corresponding wrapper class has a raw constructor.
    '''
    find_wrappable_function_with_arg0_type_cache_populate( tu)

    ret = find_wrappable_function_with_arg0_type_cache.get( structname, [])
    if state.state_.show_details(structname):
        jlib.log('{structname=}: {len(ret)=}:')
        for i in ret:
            jlib.log('    {i}')
    return ret
find_struct_cache = None


def find_struct( tu, structname, require_definition=True):
    '''
    Finds definition of struct.
    Args:
        tu:
            Translation unit.
        structname:
            Name of struct to find.
        require_definition:
            Only return cursor if it is for definition of structure.

    Returns cursor for definition or None.
    '''
    structname = util.clip( structname, 'struct ')   # Remove any 'struct ' prefix.
    global find_struct_cache
    if find_struct_cache is None:
        find_struct_cache = dict()
        for cursor in tu.cursor.get_children():
            already = find_struct_cache.get( cursor.spelling)
            if already is None:
                find_struct_cache[ cursor.spelling] = cursor
            elif cursor.is_definition() and not already.is_definition():
                find_struct_cache[ cursor.spelling] = cursor
    ret = find_struct_cache.get( structname)
    if not ret:
        return
    if require_definition and not ret.is_definition():
        return
    return ret


def find_name( cursor, name, nest=0):
    '''
    Returns cursor for specified name within <cursor>, or None if not found.

    name:
        Name to search for. Can contain '.' characters; we look for each
        element in turn, calling ourselves recursively.

    cursor:
        Item to search.
    '''
    if cursor.spelling == '':
        # Anonymous item; this seems to occur for (non-anonymous) unions.
        #
        # We recurse into children directly.
        #
        for c in cursor.get_children():
            ret = find_name_internal( c, name, nest+1)
            if ret:
                return ret

    d = name.find( '.')
    if d >= 0:
        head, tail = name[:d], name[d+1:]
        # Look for first element then for remaining.
        c = find_name( cursor, head, nest+1)
        if not c:
            return
        ret = find_name( c, tail, nest+2)
        return ret

    for c in cursor.type.get_canonical().get_fields():
        if c.spelling == '':
            ret = find_name( c, name, nest+1)
            if ret:
                return ret
        if c.spelling == name:
            return c
