#!/usr/bin/env python3

import sys
import logging
from typing import List, Dict, Set, TextIO
import pprint

import xml.etree.ElementTree


###############################################################################
def rename(name: str):
    return name


###############################################################################
class Registry:
    types: Dict[str, object] = {}
    extensions: Dict = {}
    features: Dict = {}
    applied: Set = set()

    def __init__(self):
        self.types['API Constants'] = Unscoped('API Constants')

    def _serialise(self, name: str, queued: Set[str]):
        if name in queued:
            return []

        result = []
        obj = self.types[name]

        for d in obj.depends:
            if d == name:
                continue
            result += self._serialise(d, queued)

        assert name not in queued
        queued.add(name)
        result += [obj]

        return result

    def serialise(self, platform: Set[str]):
        required = []

        for (_, f) in self.features.items():
            required += f.apply(self)
            required.append(f.name)

        for e in self.extensions:
            required += self.extensions[e].apply(self, platform)

        queued = set()
        result = []

        for r in required:
            result += self._serialise(r, queued)

        return result


###############################################################################
class Type(object):
    """
    The base class for all object defined in the Vulkan API.

    This includes (but is not limited to) types, like structures; and values,
    like constants.
    """
    def __init__(self, name: str, depends: List[str] = None):
        assert name

        self.name = name
        self.depends = depends or []

        assert isinstance(self.depends, list)
        for i in self.depends:
            assert isinstance(i, str)

    def depends(self):
        return self.depends

    def declare(self):
        return ""

    def define(self, reg: Registry):
        return ""


###############################################################################
class AliasType(Type):
    """
    A type that is an alias for another type.

    May be serialised using an appropriate host language facility
    (eg, a typedef)
    """
    def __init__(self, name: str, target: str, depends: List[str] = None):
        depends = depends or []
        super().__init__(name, depends=depends+[target])
        self.target = target

    def declare(self):
        return f"using {rename(self.name)} = {rename(self.target)};"


# -----------------------------------------------------------------------------
class AliasValue(Type):
    """
    A value that is an alias for another value.

    May be serialised using an appropriate host language facility.
    """
    def __init__(self, name: str, target: str):
        super().__init__(name, depends=[target])
        self.target = target
        self.value = target

    def declare(self):
        return "constexpr auto %(name)s = %(target)s;" % {
            "name": rename(self.name),
            "target": rename(self.target),
        }


# -----------------------------------------------------------------------------
class Placeholder(Type):
    def __init__(self, name: str):
        super().__init__(name)


# -----------------------------------------------------------------------------
class Unscoped(Type):
    def __init__(self, name: str):
        super().__init__(name)
        self.values = []

    def declare(self):
        return "\n".join(t.declare() for t in self.values)

    def define(self, reg):
        return "\n".join(t.define(reg.types) for t in self.values)


###############################################################################
class Include(Type):
    def __init__(self, node):
        assert node.tag == 'type'
        assert node.attrib['category'] == 'include'

        super().__init__(node.attrib['name'])

        self.directive = node.text

    def declare(self):
        return self.directive or "#include <%s>" % self.name


# -----------------------------------------------------------------------------
class Define(Type):
    def __init__(self, node):
        assert node.tag == 'type'
        assert node.attrib['category'] == 'define'

        name = node.attrib.get('name') or node.find('name').text
        super().__init__(name)

        self.directive = "".join(node.itertext())

    def declare(self):
        return self.directive


###############################################################################
class Bitmask(Type):
    def __init__(self, node):
        assert node.tag == 'type'
        assert node.attrib['category'] == 'bitmask'

        n = node.find('name').text
        t = node.find('type').text

        super().__init__(n, depends=[t])

        self.type = t
        self.requires = node.attrib.get('requires')
        if self.requires:
            self.depends.append(self.requires)

    def declare(self):
        return "using %(name)s = %(type)s;" % {
            "name": self.name,
            "type": self.type
        }

    def define(self, reg: Registry):
        return self.declare()


###############################################################################
class Handle(Type):
    parents: List[str]
    type: str

    def __init__(self, node):
        assert node.tag == 'type'
        assert node.attrib['category'] == 'handle'

        n = node.find('name').text
        t = node.find('type').text
        assert t

        super().__init__(n, depends=[t])
        self.type = t

        parents = node.attrib.get('parent', None)
        self.parents = parents.split(',') if parents else []

    def declare(self):
        return "struct %(name)s_t; using %(name)s = %(name)s_t*;" % {
            "name": self.name,
            "type": self.type
        }

    def has_parent(self, name: str, reg: Registry) -> bool:
        """
        Recursively check if this type is derived from a given parent type.
        """
        assert name
        assert reg

        if self.name == name:
            return True

        if not self.parents:
            return False
        if name in self.parents:
            return True

        for p in self.parents:
            if reg.types[p].has_parent(name, reg):
                return True
        return False


###############################################################################
class Enum(Type):
    def __init__(self, node):
        assert node.tag == 'type'
        assert node.attrib['category'] == 'enum'

        name = node.attrib['name']
        super().__init__(name, depends=["VkEnum"])

        self.values = {}

    def __setitem__(self, key: str, value):
        assert isinstance(value, Constant) or isinstance(value, AliasValue)
        self.values[key] = value

    def declare(self):
        return ""

    def define(self, reg: Registry):
        values = ("%(name)s = %(value)s" % {"name": k, "value": v.value} for (k, v) in self.values.items())

        return "enum %(name)s : int32_t { %(values)s };" % {
            "name": self.name,
            "values": ", ".join(values)
        }


###############################################################################
class BaseType(AliasType):
    """
    Represents fundamental types that aliases of system provided types and used
    extensively by the base API. eg, VkBool32
    """

    def __init__(self, node):
        assert node.tag == 'type'
        assert node.attrib['category'] == 'basetype'

        super().__init__(
            node.find('name').text,
            node.find('type').text
        )


###############################################################################
class FuncPointer(Type):
    def __init__(self, node):
        assert node.tag == 'type'
        assert node.attrib['category'] == 'funcpointer'

        name = node.find('name').text

        self.params = list(map(lambda x: x.text, node.findall('./type')))
        self.text = "".join(node.itertext())

        super().__init__(name, depends=['VkBool32']+self.params)

    def declare(self):
        return self.text


###############################################################################
class POD(Type):
    def __init__(self, node):
        assert node.tag == 'type'
        assert node.attrib['category'] in ['struct', 'union']

        super().__init__(node.attrib['name'])
        self._node = node
        self._category = node.attrib['category']

        # sometimes there are enums hiding in the member fields being used as array sizes
        self.depends += list(e.text for e in node.findall('.//enum'))
        self.depends += list(t.text for t in node.findall('.//type'))

        self._members = []

        for member in node.findall('./member'):
            t = member.find('type').text
            n = member.find('name').text

            comment = member.find('comment')
            if comment is not None:
                member.remove(comment)
            code = " ".join(member.itertext())

            self._members.append({'code': code, 'type': t, 'name': n})

    def declare(self):
        return "%(category)s %(name)s;" % {
            'category': self._category,
            'name': rename(self.name)
        }

    def define(self, reg: Registry):
        return "%(category)s %(name)s {\n%(members)s\n};" % {
            'category': self._category,
            'name': rename(self.name),
            'members': "\n".join(m['code'] + ';' for m in self._members)
        }


# -----------------------------------------------------------------------------
class Struct(POD):
    def __init__(self, node):
        super().__init__(node)


# -----------------------------------------------------------------------------
class Union(POD):
    def __init__(self, node):
        super().__init__(node)


###############################################################################
class Constant(Type):
    def __init__(self, node, **kwargs):
        assert node.tag == 'enum'

        name = node.attrib['name']
        super().__init__(name)

        if 'offset' in node.attrib:
            assert 'extends' in node.attrib

            number = int(kwargs['extnumber'])
            offset = int(node.attrib['offset'])
            self.value = 1000000000 + 1000 * number + offset

            if 'dir' in node.attrib:
                self.value *= -1
        elif 'value' in node.attrib:
            self.value = node.attrib['value']
        elif 'bitpos' in node.attrib:
            self.value = "1 << %s" % node.attrib['bitpos']
        else:
            raise RuntimeError("Unknown constant value type")

    def declare(self):
        return "constexpr auto %(name)s = %(value)s;" % {
            "name": self.name,
            "value": self.value
        }


###############################################################################
class Command(Type):
    class Param(Type):
        name: str
        """An string that can be used to refer to the parameter variable"""
        type: str
        """The name of this parameter's dependant type"""
        param: str
        """
        The components of this type for a C definition (ie, includes
        pointer, const, other decorations, _and_ the variable name (which must
        be the same as self.name for a useful system).
        """

        def __init__(self, name:str, type:str, param:str, depends:List[str]):
            super().__init__(
                name=name,
                depends=depends,
            )

            self.type = type
            self.param = param

        def __repr__(self) -> str:
            return f"{{ name: '{self.name}', type: '{self.type}', param: '{self.param}' }}"

        def is_pointer(self):
            return '*' in self.param

    def __init__(self, name: str, result: str, params: List[Param], depends: List[str] = None):
        super().__init__(name)

        self.result = result
        self.params = params
        self.depends += depends or []

    def __repr__(self) -> str:
        return f"{{ name: '{self.name}', result: '{self.result}', param: {self.params} }}"

    def declare(self):
        return 'extern "C" %(result)s %(name)s [[gnu::visibility("default")]] (%(params)s) noexcept;' % {
            'name': rename(self.name),
            'result': self.result,
            'params': ", ".join(p.param for p in self.params)
        }

    def is_instance(self, reg: Registry):
        assert reg

        if not self.params:
            return False

        first_name = self.params[0].type
        first_obj = reg.types[first_name]

        if not isinstance(first_obj, Handle):
            return True

        instance = first_obj.name == 'VkInstance'
        physical = first_obj.name == 'VkPhysicalDevice'
        return instance or physical

    def is_device(self, reg: Registry):
        if not self.params:
            return False

        first_name = self.params[0].type
        first_obj = reg.types[first_name]
        if not isinstance(first_obj, Handle):
            return False

        for i in ['VkDevice', 'VkQueue', 'VkCommandBuffer']:
            if first_obj.has_parent(i, reg):
                return True

        return False


###############################################################################
class Require(object):
    def __init__(self, values, depends: List[str]):
        self.values = values or []
        self.depends = depends or []

    def apply(self, reg: Registry, extnumber=None):
        required = []
        required += self.depends

        for value in self.values:
            name = value.attrib['name']

            if len(value.attrib) == 1:
                assert 'name' in value.attrib
                required.append(name)
                continue

            if 'extends' not in value.attrib:
                obj = Constant(value)
                owner = reg.types['API Constants']
                owner.values.append(obj)
                continue

            owner = reg.types[value.attrib['extends']]

            if 'alias' in value.attrib:
                owner[name] = AliasValue(name, value.attrib['alias'])
                required.append(owner.name)
            elif value.tag == 'enum':
                owner[name] = Constant(value, extnumber=extnumber or int(value.attrib.get('extnumber', '0')))
                required.append(owner.name)
            elif value.tag == 'command':
                required.append(name)
            else:
                raise RuntimeError("Unknown type")

        return required


# -----------------------------------------------------------------------------
class Feature(Type):
    def __init__(self, name: str, requires: List[Require] = []):
        super().__init__(name)
        self.requires = requires

    def define(self, reg: Registry):
        return "#define %s" % self.name

    def apply(self, reg: Registry):
        logging.info("Applying feature:", self.name, file=sys.stderr)

        result = []
        for r in self.requires:
            result += r.apply(reg)

        return result


# -----------------------------------------------------------------------------
class Extension(Type):
    def __init__(self, root):
        assert root.tag == 'extension'

        name = root.attrib['name']
        super().__init__(name)

        if 'requires' in root.attrib:
            self.depends += root.attrib['requires'].split(',')

        self.number = int(root.attrib['number'])
        self.platform = root.attrib.get('platform')

        self.requires = []

        for node in root:
            if node.tag == 'require':
                self.requires.append(parse_require(node))
            else:
                raise RuntimeError("Unknown extension node")

    def apply(self, reg: Registry, platform: Set[str]):
        if self.name in reg.applied:
            return []
        reg.applied.add(self.name)

        if self.platform and self.platform not in platform:
            return []

        required = []

        for dep in self.depends:
            required = reg.extensions[dep].apply(reg, platform)

        logging.info("Applying extension:", self.name, file=sys.stderr)
        for node in self.requires:
            required += node.apply(reg, extnumber=self.number)
        return required


###############################################################################
def ignore_node(types: Dict[str, Type], root):
    types, root
    pass


# -----------------------------------------------------------------------------
parse_comment = ignore_node
parse_vendorids = ignore_node
parse_platforms = ignore_node
parse_tags = ignore_node


# -----------------------------------------------------------------------------
def parse_types(reg: Registry, root):
    assert root.tag == 'types'

    for t in root.findall('type'):
        name = t.attrib.get ('name') or t.find('name').text
        assert name not in reg.types

        if 'alias' in t.attrib:
            name = t.attrib['name']
            target = t.attrib['alias']

            reg.types[name] = AliasType(name, target)
            continue

        category = t.attrib.get ('category')

        # if we don't have a category we should have a bare type that has a
        # dependency on something like a header.
        #
        # eg, 'Display' depends on 'X11/Xlib.h'
        if not category:
            reg.types[name] = Placeholder(name)
        else:
            # Whitelist the known types so we don't accidentally instantiate
            # something whacky

            supported_categories = {
                'include': Include,
                'define': Define,
                'bitmask': Bitmask,
                'basetype': BaseType,
                'handle': Handle,
                'enum': Enum,
                'funcpointer': FuncPointer,
                'struct': Struct,
                'union': Union,
            }

            concrete = supported_categories.get(category, None)
            if concrete:
                reg.types[name] = concrete(t)
            else:
                raise RuntimeError('unhandled type')

        if 'requires' in t.attrib:
            reg.types[name].depends.append(t.attrib['requires'])


# -----------------------------------------------------------------------------
def parse_enums(reg: Registry, root):
    assert root.tag == 'enums'
    ownername = root.attrib['name']
    owner = reg.types[ownername] if ownername != 'API Constants' else reg.types

    for node in root.findall('./enum'):
        valuename = node.attrib.get('name')

        assert 'requires' not in node.attrib

        if 'alias' in node.attrib:
            owner[valuename] = AliasValue(valuename, node.attrib['alias'])
        else:
            owner[valuename] = Constant(node)

#------------------------------------------------------------------------------
def parse_param(root) -> Command.Param:
    assert root.tag == 'param'

    param = ""
    for i in root.iter():
        param += i.text or ""
        param += i.tail or ""
    # normalise whitespace
    param = " ".join(param.split())

    name = root.find('name').text
    type = root.find('type').text
    depends = [root.find('type').text]

    return Command.Param(
        name=name,
        type=type,
        param=param,
        depends=depends,
    )


# -----------------------------------------------------------------------------
def parse_commands(reg: Registry, root):
    assert root.tag == 'commands'

    for node in root.findall('./command'):
        name = node.attrib.get('name') or node.find('./proto/name').text
        assert name not in reg.types

        if 'alias' in node.attrib:
            reg.types[name] = AliasValue(name, node.attrib['alias'])
            continue

        proto = node.find('proto')
        name = proto.find('name').text

        result = proto.find('type').text
        params = [parse_param(p) for p in node.findall('./param')]
        depends = [result]
        for p in params:
            depends += p.depends

        reg.types[name] = Command(name, result, params, depends)


# -----------------------------------------------------------------------------
def parse_require(root) -> Require:
    assert root.tag == 'require'

    values = []
    depends = []

    for node in root:
        if node.tag == 'enum':
            values.append(node)
        elif node.tag in ['command', 'type']:
            depends.append(node.attrib['name'])
        elif node.tag in ['comment']:
            pass
        else:
            raise RuntimeError("Unknown requires node")

    return Require(values=values, depends=depends)

##-----------------------------------------------------------------------------
def parse_feature(reg: Registry, root):
    assert root.tag == 'feature'

    name = root.attrib['name']
    assert name not in reg.features

    requires = []
    for node in root:
        if 'require' == node.tag:
            requires.append(parse_require(node))
        else:
            raise RuntimeError("Unhandled feature node")

    reg.features[name] = Feature(name, requires)
    reg.types[name] = reg.features[name]


# -----------------------------------------------------------------------------
def parse_extensions(reg: Registry, root):
    assert root.tag == 'extensions'

    for node in root.findall('./extension'):
        name = node.attrib['name']
        assert name not in reg.extensions

        reg.extensions[name] = Extension(node)


###############################################################################
def write_header(dst: TextIO, q: List[Type], reg: Registry):
    dst.write("#pragma once\n")

    # Write the declarations and definitions for all types.
    for obj in q:
        dst.write(obj.declare())
        dst.write('\n')
        dst.write(obj.define(reg))
        dst.write('\n')

    # Define the default case for device and instance type traits.
    dst.write("""
    #include <type_traits>

    /// A type trait that tests if a Vulkan type is an instance type
    template <typename NativeT>
    struct is_instance:
        public std::false_type
    {};


    /// A type trait that tests if a Vulkan type is a device type
    template <typename NativeT>
    struct is_device:
        public std::false_type
    {};


    template <typename T>
    constexpr auto is_instance_v = is_instance<T>::value;

    template <typename T>
    constexpr auto is_device_v = is_device<T>::value;
    """)

    # Specialise traits for device and instance types.
    for obj in q:
        if not isinstance(obj, Handle):
            continue

        device_value = "true_type" if obj.has_parent("VkDevice", reg) else "false_type"
        instance_value = "true_type" if obj.has_parent("VkInstance", reg) else "false_type"

        dst.write(f"""
        template <> struct is_instance<{obj.name}>: public std::{instance_value} {{ }};
        template <> struct is_device<{obj.name}>: public std::{device_value} {{ }};
        """)


# -----------------------------------------------------------------------------
def write_load(dst: TextIO, q: List[Type], reg: Registry):
    commands = [i for i in q if isinstance(i, Command)]

    collections = {
        'instance': Command.is_instance,
        'device': Command.is_device,
    }

    dst.write(f"""
    #pragma once

    #include <cruft/vk/vk.hpp>

    #include <cruft/util/preprocessor.hpp>

    namespace cruft::vk::load {{
    class vendor;

    #define MAP_COMMANDS(FUNC) MAP0(FUNC,{",".join(i.name for i in commands)})

    """)

    for name, test in collections.items():
        curr = [i for i in commands if     test(i, reg)]
        next = [i for i in commands if not test(i, reg)]
        commands = next

        dst.write(f"""
            #define MAP_{name.upper()}_COMMANDS(FUNC) \
                MAP0(FUNC,{",".join([i.name for i in curr])})

            struct {name}_table{{
        """)

        # Generate the vtable entries for instance methods
        dst.writelines((
            f"{obj.result} (*{obj.name}) ({','.join(p.param for p in obj.params)}) = nullptr;"
            for obj in curr
        ))

        dst.write("""
        };
        """)

    dst.write("""
        struct vendor_table;
        extern cruft::vk::load::vendor_table const *v_table [[gnu::visibility("default")]];
        extern cruft::vk::load::instance_table const *i_table [[gnu::visibility("default")]];
    }
    """)


# -----------------------------------------------------------------------------
def write_dispatch(dst: TextIO, q: List[Type], reg: Registry):
    dst.write("""
    #include <cruft/vk/vk.hpp>
    #include <cruft/vk/load/vtable.hpp>
    #include <cruft/vk/load/dispatch.hpp>

    #include <cruft/util/debug.hpp>
    
    #include <cstring>

    #pragma GCC diagnostic ignored "-Wunused-parameter"

    template <typename HandleT, typename TableT>
    struct indirect {
        HandleT handle;
        TableT table;
    };
    """)

    implementations = {
        'vkCreateInstance': """
            auto res = std::make_unique<indirect<VkInstance,cruft::vk::load::instance_table>> ();
            auto err = cruft::vk::load::i_table->vkCreateInstance (pCreateInfo, pAllocator, &res->handle);
            if (err != VK_SUCCESS)
                return err;
            
            #define GET(NAME) res->table.NAME = reinterpret_cast<decltype(&NAME)> (cruft::vk::load::v_table->vk_icdGetInstanceProcAddr (res->handle, #NAME));
            MAP_INSTANCE_COMMANDS(GET)
            #undef GET
            
            #define GET(NAME) if (!res->table.NAME) res->table.NAME = reinterpret_cast<decltype(&NAME)> (res->table.vkGetInstanceProcAddr (res->handle, #NAME));
            MAP_INSTANCE_COMMANDS(GET)
            #undef GET
            
            *pInstance = (VkInstance)res.release (); 
            return err;
        """,

        'vkGetInstanceProcAddr': """
            #define ATTEMPT(NAME) if (!strcmp (#NAME, pName)) return reinterpret_cast<PFN_vkVoidFunction> (&NAME);
            MAP_INSTANCE_COMMANDS(ATTEMPT)
            #undef ATTEMPT
            return nullptr;
        """,

        'vkCreateDevice': """
            (void)physicalDevice;
            (void)pCreateInfo;
            (void)pAllocator;
            (void)pDevice;
            unimplemented (); 
        """,

        'vkEnumeratePhysicalDevices': """
            auto const entry = reinterpret_cast<
                indirect<VkInstance,cruft::vk::load::instance_table> const*
            > (instance);
            
            if (!pPhysicalDeviceCount || !pPhysicalDevices) {
                return (entry->table.vkEnumeratePhysicalDevices)(
                    entry->handle, pPhysicalDeviceCount, pPhysicalDevices
                );
            }
            
            std::vector<VkPhysicalDevice> res (*pPhysicalDeviceCount);
            auto err = (entry->table.vkEnumeratePhysicalDevices)(
                entry->handle, pPhysicalDeviceCount, res.data ()
            );
            res.resize (*pPhysicalDeviceCount);
            
            if (err != VK_SUCCESS)
                return err;
                
            for (uint32_t i = 0; i < *pPhysicalDeviceCount; ++i) {
                auto wrapped = std::make_unique<indirect<VkPhysicalDevice,cruft::vk::load::instance_table>> ();
                wrapped->handle = res[i];
                
                #define GET(NAME) wrapped->table.NAME = wrapped->table.NAME ?: reinterpret_cast<decltype(&NAME)> (entry->table.vkGetInstanceProcAddr (entry->handle, #NAME));
                MAP_INSTANCE_COMMANDS(GET)
                #undef GET
                
                #define GET(NAME) wrapped->table.NAME = wrapped->table.NAME ?: reinterpret_cast<decltype(&NAME)> (cruft::vk::load::v_table->vk_icdGetInstanceProcAddr (entry->handle, #NAME));
                MAP_INSTANCE_COMMANDS(GET)
                #undef GET
                
                #define GET(NAME) wrapped->table.NAME = wrapped->table.NAME ?: reinterpret_cast<decltype(&NAME)> (cruft::vk::load::v_table->vk_icdGetPhysicalDeviceProcAddr (entry->handle, #NAME));
                MAP_INSTANCE_COMMANDS(GET)
                #undef GET
                
                std::clog << "physical_device[" << i << "]; wrapped: " << wrapped.get() << ", native: " << (void*)wrapped->handle << '\\n';
                pPhysicalDevices[i] = (VkPhysicalDevice)wrapped.release ();
            }
            
            return err;
        """
    }

    for obj in (i for i in q if isinstance(i, Command)):
        first_arg = reg.types[obj.params[0].type]

        instance_forward = f"""
            return cruft::vk::load::i_table->{obj.name} ({", ".join(p.name for p in obj.params)});
        """

        if obj.is_instance(reg):
            table = 'instance'
        elif obj.is_device(reg):
            table = 'device'
        else:
            raise Exception(f"Unhandled command type for {obj}")

        if obj.params:
            last_param = obj.params[-1]
            last_obj = reg.types[last_param.type]
            is_creating = isinstance(last_obj, Handle) and last_param.is_pointer()
        else:
            is_creating = False

        if obj.is_instance(reg) and obj.params[0].type not in ['VkInstance', 'VkPhysicalDevice']:
            forwarding = f"""
            if (::cruft::vk::load::i_table->{obj.name})
                return ::cruft::vk::load::i_table->{obj.name} ({', '.join (i.name for i in obj.params)});
            else {{
                auto ptr= cruft::vk::load::v_table->vk_icdGetInstanceProcAddr (nullptr, "{obj.name}");
                return ((decltype({obj.name})*) (ptr)) ({', '.join (i.name for i in obj.params)});
            }}
            """
        else:
            forwarding = f"""
                if constexpr (std::is_same_v<{obj.params[0].type}, VkInstance> ||
                              std::is_same_v<{obj.params[0].type}, VkPhysicalDevice>) {{
                    if ({obj.params[0].name} == VK_NULL_HANDLE) {{
                        auto ptr= cruft::vk::load::v_table->vk_icdGetInstanceProcAddr (nullptr, "{obj.name}");
                        return ((decltype({obj.name})*) (ptr)) ({', '.join (i.name for i in obj.params)});
                    }}
                }}

                auto const entry = reinterpret_cast<
                    indirect<{obj.params[0].type},cruft::vk::load::{table}_table> const*
                > ({obj.params[0].name});

                std::clog << "{obj.name}\\n";
                return (entry->table.{obj.name})(
                    {", ".join(['entry->handle'] + [p.name for p in obj.params[1:]])}
                );
            """

        dst.write(f"""
        extern "C" {obj.result} {rename(obj.name)} ({", ".join(p.param for p in obj.params)}) noexcept {{
            {implementations.get(obj.name, forwarding)}
        }}
        """)


###############################################################################
import argparse


# -----------------------------------------------------------------------------
def main():
    logging.getLogger().setLevel(logging.WARNING)

    parser = argparse.ArgumentParser(description='Transform XML API specification into C++ headers')
    parser.add_argument('--src', type=str, help='the path to the XML file to transform')
    parser.add_argument('--dst', type=str, help='the output path for the result')
    parser.add_argument('--load', type=str, help='the output path for the loading routines')
    parser.add_argument('--dispatch', type=str, help="the output path for function dispatch")
    parser.add_argument(
        '--platform',
        type=str,
        action='append',
        help='a platform to generate output for. may be specific multiple times"'
    )

    args = parser.parse_args()

    # Get a copy of the specification XML
    with open(args.src, 'r') as src:
        tree = xml.etree.ElementTree.parse(src)
    root = tree.getroot()

    # Find a parser for each of the nodes in the XML
    reg = Registry()
    for node in root:
        target = "parse_%s" % node.tag
        globals()[target](reg, node)

    # Override some requested system types so that they fit more naturally in
    # our environment. eg, use appropriate C++ types, or cruft library
    # wrappers.
    reg.types['windows.h'].name = 'cruft/util/win32/windows.hpp'
    reg.types['void*'] = Placeholder('void*')
    reg.types['nullptr'] = Placeholder('nullptr')
    reg.types['VkEnum'] = AliasType('VkEnum', 'int32_t')
    reg.types['VK_DEFINE_NON_DISPATCHABLE_HANDLE'] = AliasType("VK_DEFINE_NON_DISPATCHABLE_HANDLE", "uint64_t")
    reg.types['VK_DEFINE_HANDLE'] = AliasType("VK_DEFINE_HANDLE", "void*")
    reg.types['VK_NULL_HANDLE'] = AliasValue("VK_NULL_HANDLE", "nullptr")

    #reg.types['vk_icdGetInstanceProcAddr'] = Command(
    #    name='vk_icdGetInstanceProcAddr',
    #    result='void*',
    #    params=[
    #        Command.Param(
    #            name='instance',
    #            type='VkInstance',
    #            param='VkInstance instance',
    #            depends=['VkInstance']
    #        ),
    #        Command.Param(
    #            name='pName',
    #            type='void*',
    #            param='char const *pName',
    #            depends=[]
    #        ),
    #    ]
    #)
    #reg.types['vk_icdGetPhysicalDeviceProcAddr'] = Command(
    #    name='vk_icdGetPhysicalDeviceProcAddr',
    #    result='void*',
    #    params=[
    #        Command.Param(
    #            name='instance',
    #            type='VkInstance',
    #            param='VkInstance instance',
    #            depends=['VkInstance']
    #        ),
    #        Command.Param(
    #            name='pName',
    #            type='void*',
    #            param='char const *pName',
    #            depends=[]
    #        ),
    #    ]
    #)

    #icd = Feature(
    #    "__nerdcruft_icd",
    #    requires=[
    #        Require(None, ["vk_icdGetInstanceProcAddr"]),
    #        Require(None, ["vk_icdGetPhysicalDeviceProcAddr"])
    #    ]
    #)
    #reg.features['__nerdcruft_icd'] = icd
    #reg.types['__nerdcruft_icd'] = reg.features['__nerdcruft_icd']

    # Request serialisation of all features
    #features = [Feature(n) for n in root.findall('./feature')]
    #features = dict((f.name,f) for f in features)

    #reg.extensions['VK_KHR_surface'].apply(reg, platform='xcb')

    # Request a minimal set of extensions that will almost certainly be
    # required for all applications.
    extensions = ["VK_KHR_swapchain", "VK_EXT_debug_report", "VK_KHR_external_memory"]
    q = reg.serialise(args.platform)

    # Finally write out the header, vtables, and dispatch code.
    with open(args.dst, 'w') as dst:
        write_header(dst, q, reg)

    with open(args.load, 'w') as dst:
        write_load(dst, q, reg)

    with open(args.dispatch, 'w') as dst:
        write_dispatch(dst, q, reg)


# -----------------------------------------------------------------------------
if __name__ == '__main__':
    main()