use std::{
	borrow::Cow,
	collections::HashMap,
	fmt,
};

use clang::{Availability, Entity, EntityKind};
use once_cell::sync::Lazy;
use regex::Regex;

use crate::{
	Class,
	comment,
	DefaultElement,
	DefinitionLocation,
	DependentType,
	DependentTypeMode,
	Element,
	EntityElement,
	EntityExt,
	Field,
	FieldTypeHint,
	GeneratorEnv,
	reserved_rename,
	settings::{self, SliceHint},
	StrExt,
	StringExt,
	type_ref::{Dir, StrType},
	TypeRef,
};

#[derive(Debug, PartialEq)]
pub enum OperatorKind {
	Unsupported,
	Index,
	Add,
	Sub,
	Mul,
	Div,
	Deref,
}

impl OperatorKind {
	pub fn new(token: &str, arg_count: usize) -> Self {
		match token.trim() {
			"[]" => {
				OperatorKind::Index
			}
			"+" => {
				OperatorKind::Add
			}
			"-" => {
				OperatorKind::Sub
			}
			"*" => {
				if arg_count == 0 {
					OperatorKind::Deref
				} else {
					OperatorKind::Mul
				}
			}
			"/" => {
				OperatorKind::Div
			}
			_ => {
				OperatorKind::Unsupported
			},
		}
	}
}

#[derive(Debug)]
pub enum Kind<'tu> {
	Function,
	FunctionOperator(OperatorKind),
	Constructor(Class<'tu>),
	InstanceMethod(Class<'tu>),
	StaticMethod(Class<'tu>),
	FieldAccessor(Class<'tu>),
	ConversionMethod(Class<'tu>),
	InstanceOperator(Class<'tu>, OperatorKind),
	GenericFunction,
	GenericInstanceMethod(Class<'tu>),
}

#[derive(Copy, Clone, Debug, PartialEq)]
pub enum FunctionTypeHint {
	None,
	FieldSetter,
	Specialized(&'static HashMap<&'static str, &'static str>),
}

#[derive(Clone)]
pub struct Func<'tu> {
	entity: Entity<'tu>,
	type_hint: FunctionTypeHint,
	name_hint: Option<&'tu str>,
	gen_env: &'tu GeneratorEnv<'tu>,
}

impl<'tu> Func<'tu> {
	pub fn new(entity: Entity<'tu>, gen_env: &'tu GeneratorEnv<'tu>) -> Self {
		Self { entity, type_hint: FunctionTypeHint::None, name_hint: None, gen_env }
	}

	pub fn new_ext(entity: Entity<'tu>, type_hint: FunctionTypeHint, name_hint: Option<&'tu str>, gen_env: &'tu GeneratorEnv<'tu>) -> Self {
		Self { entity, type_hint, name_hint, gen_env }
	}

	pub fn set_name_hint(&mut self, name_hint: Option<&'tu str>) {
		self.name_hint = name_hint;
	}

	pub fn name_hint(&self) -> Option<&'tu str> {
		self.name_hint
	}

	pub fn type_hint(&self) -> FunctionTypeHint {
		self.type_hint
	}

	pub fn kind(&self) -> Kind<'tu> {
		const OPERATOR: &str = "operator";
		match self.entity.get_kind() {
			EntityKind::FunctionDecl => {
				if let Some(operator) = self.entity.cpp_localname().strip_prefix(OPERATOR) {
					let arg_count = self.entity.get_arguments().map_or(0, |v| v.len());
					Kind::FunctionOperator(OperatorKind::new(operator.trim(), arg_count))
				} else {
					Kind::Function
				}
			}
			EntityKind::Constructor => {
				Kind::Constructor(Class::new(
					self.entity.get_semantic_parent().expect("Can't get parent of constructor"),
					self.gen_env,
				))
			}
			EntityKind::Method => {
				let class = Class::new(
					self.entity.get_semantic_parent().expect("Can't get parent of method"),
					self.gen_env,
				);
				if self.entity.is_static_method() {
					Kind::StaticMethod(class)
				} else if let Some(operator) = self.entity.cpp_localname().strip_prefix(OPERATOR) {
					let arg_count = self.entity.get_arguments().map_or(0, |v| v.len());
					Kind::InstanceOperator(class, OperatorKind::new(operator.trim(), arg_count))
				} else {
					Kind::InstanceMethod(class)
				}
			}
			EntityKind::FieldDecl | EntityKind::VarDecl => {
				Kind::FieldAccessor(Field::new(self.entity, self.gen_env).parent())
			}
			EntityKind::ConversionFunction => {
				Kind::ConversionMethod(Class::new(
					self.entity.get_semantic_parent().expect("Can't get parent of method"),
					self.gen_env,
				))
			}
			EntityKind::FunctionTemplate => {
				match self.entity.get_template_kind() {
					Some(EntityKind::Method) => {
						Kind::GenericInstanceMethod(Class::new(
							self.entity.get_semantic_parent().expect("Can't get parent of generic method"),
							self.gen_env,
						))
					}
					_ => {
						Kind::GenericFunction
					}
				}
			}
			_ => unreachable!("Unknown function entity: {:#?}", self.entity)
		}
	}

	pub fn as_constructor(&self) -> Option<Class<'tu>> {
		if let Kind::Constructor(out) = self.kind() {
			Some(out)
		} else {
			None
		}
	}

	pub fn as_instance_method(&self) -> Option<Class<'tu>> {
		match self.kind() {
			Kind::InstanceMethod(out) | Kind::FieldAccessor(out) | Kind::GenericInstanceMethod(out)
			| Kind::ConversionMethod(out) | Kind::InstanceOperator(out, ..) => {
				Some(out)
			}
			_ => {
				None
			}
		}
	}

	pub fn as_static_method(&self) -> Option<Class<'tu>> {
		if let Kind::StaticMethod(out) = self.kind() {
			Some(out)
		} else {
			None
		}
	}

	pub fn as_field_accessor(&self) -> Option<Field<'tu>> {
		if let Kind::FieldAccessor(..) = self.kind() {
			Some(Field::new(self.entity, self.gen_env))
		} else {
			None
		}
	}

	pub fn as_field_setter(&self) -> Option<Field<'tu>> {
		if self.as_field_accessor().is_some() && self.type_hint == FunctionTypeHint::FieldSetter {
			Some(Field::new_ext(self.entity, FieldTypeHint::FieldSetter, self.gen_env))
		} else {
			None
		}
	}

	pub fn as_conversion_method(&self) -> Option<Class<'tu>> {
		if let Kind::ConversionMethod(out) = self.kind() {
			Some(out)
		} else {
			None
		}
	}

	pub fn as_operator(&self) -> Option<(Option<Class<'tu>>, OperatorKind)> {
		match self.kind() {
			Kind::FunctionOperator(kind) => {
				Some((None, kind))
			}
			Kind::InstanceOperator(cls, kind) => {
				Some((Some(cls), kind))
			}
			_ => {
				None
			}
		}
	}

	pub fn is_const(&self) -> bool {
		if settings::FORCE_CONSTANT_METHOD.contains(self.cpp_fullname().as_ref()) {
			true
		}
		else if let Some(fld) = self.as_field_accessor() {
			self.type_hint != FunctionTypeHint::FieldSetter && {
				let type_ref = fld.type_ref();
				type_ref.constness().is_const() || type_ref.is_copy() || matches!(type_ref.as_string(), Some(Dir::In(StrType::CvString)) | Some(Dir::In(StrType::StdString)))
			}
		} else {
			self.entity.is_const_method()
		}
	}

	pub fn is_abstract(&self) -> bool {
		self.entity.is_pure_virtual_method()
	}

	pub fn is_generic(&self) -> bool {
		match self.kind() {
			Kind::GenericFunction | Kind::GenericInstanceMethod(..) => {
				!self.as_specialized().is_some()
			}
			Kind::Function | Kind::Constructor(..) | Kind::InstanceMethod(..)
			| Kind::StaticMethod(..) | Kind::FieldAccessor(..) | Kind::ConversionMethod(..)
			| Kind::FunctionOperator(..) | Kind::InstanceOperator(..) => {
				false
			}
		}
	}

	pub fn is_infallible(&self) -> bool {
		self.as_field_accessor().is_some()
			|| self.gen_env.get_export_config(self.entity).map_or(false, |e| e.no_except)
	}

	pub fn is_clone(&self) -> bool {
		if self.rust_leafname() == "clone" {
			if let Some(c) = self.as_instance_method() {
				!self.has_arguments() && self.return_type().as_class().map_or(false, |r| r == c)
			} else {
				false
			}
		} else {
			false
		}
	}

	pub fn as_specialized(&self) -> Option<&'static HashMap<&'static str, &'static str>> {
		if let FunctionTypeHint::Specialized(spec) = self.type_hint {
			Some(spec)
		} else {
			None
		}
	}

	pub fn return_type(&self) -> TypeRef<'tu> {
		match self.kind() {
			Kind::Constructor(cls) => {
				cls.type_ref()
			}
			Kind::Function | Kind::InstanceMethod(..) | Kind::StaticMethod(..)
			| Kind::ConversionMethod(..) | Kind::GenericInstanceMethod(..) | Kind::GenericFunction
			| Kind::FunctionOperator(..) | Kind::InstanceOperator(..) => {
				let mut out = TypeRef::new(
					self.entity.get_result_type().expect("Can't get return type"),
					self.gen_env,
				);
				if let Some(type_ref) = out.as_reference() {
					out = type_ref
				}
				if let Some(spec) = self.as_specialized() {
					if out.is_generic() {
						let spec_type = spec.get(out.base().cpp_full().as_ref())
							.and_then(|s| self.gen_env.resolve_type(s));
						if let Some(spec_type) = spec_type {
							out.specialize(spec_type);
						}
					}
				}
				out
			}
			Kind::FieldAccessor(..) => {
				if self.type_hint == FunctionTypeHint::FieldSetter {
					TypeRef::new(self.gen_env.resolve_type("void").expect("Can't resolve void type"), self.gen_env)
				} else {
					Field::new(self.entity, self.gen_env).type_ref()
				}
			}
		}
	}

	pub fn has_arguments(&self) -> bool {
		!self.clang_arguments().is_empty()
	}

	pub fn clang_arguments(&self) -> Vec<Entity<'tu>> {
		match self.kind() {
			Kind::GenericFunction | Kind::GenericInstanceMethod(..) => {
				let mut out = vec![];
				self.entity.walk_children_while(|child| {
					if child.get_kind() == EntityKind::ParmDecl {
						out.push(child);
					}
					true
				});
				out
			}
			Kind::FieldAccessor(..) => {
				if self.type_hint == FunctionTypeHint::FieldSetter {
					vec![self.entity]
				} else {
					vec![]
				}
			}
			_ => {
				self.entity.get_arguments().expect("Can't get arguments")
			}
		}
	}

	pub fn arguments(&self) -> Vec<Field<'tu>> {
		let args = self.clang_arguments();

		let empty_hashmap = HashMap::new();
		let spec = if let Some(spec) = self.as_specialized() {
			spec
		} else {
			&empty_hashmap
		};
		let args_len = args.len();
		let func_name = self.cpp_fullname();
		let is_field_setter = self.as_field_setter().is_some();

		args.into_iter()
			.map(|a| {
				if is_field_setter {
					return Field::new_ext(a, FieldTypeHint::FieldSetter, self.gen_env)
				}

				if let Some(slice_arg) = settings::SLICE_ARGUMENT.get(&(func_name.as_ref(), args_len)) {
					match *slice_arg {
						SliceHint::ForceSlice(arg) => {
							if arg == a.rust_leafname().as_ref() {
								return Field::new_ext(a, FieldTypeHint::Slice, self.gen_env)
							}
						},
						SliceHint::ConvertSlice(ptr_arg, len_arg, len_div) => {
							let arg_name = a.rust_leafname();
							if ptr_arg == arg_name.as_ref() {
								return Field::new_ext(a, FieldTypeHint::Slice, self.gen_env)
							} else if len_arg == arg_name.as_ref() {
								return Field::new_ext(a, FieldTypeHint::SliceLen(ptr_arg, len_div), self.gen_env)
							}
						}
					}
				}

				let out = Field::new(a, self.gen_env);
				let type_ref = out.type_ref();
				if type_ref.is_generic() {
					let spec_type = spec.get(type_ref.base().cpp_full().as_ref())
						.and_then(|s| self.gen_env.resolve_type(s));
					if let Some(spec_type) = spec_type {
						return Field::new_ext(a, FieldTypeHint::Specialized(spec_type), self.gen_env);
					}
				}
				out
			})
			.collect()
	}

	pub fn dependent_types<D: DependentType<'tu>>(&self) -> Vec<D> {
		self.arguments().into_iter()
			.map(|a| a.type_ref())
			.filter(|t| !t.is_ignored())
			.map(|t| t.dependent_types())
			.flatten()
			.chain(self.return_type().dependent_types_with_mode(DependentTypeMode::ForReturn(DefinitionLocation::Module)))
			.collect()
	}

	pub fn identifier(&self) -> Cow<str> {
		let mut out: String = if self.as_field_accessor().is_some() {
			let mut out: String = self.cpp_namespace().into_owned();
			if !out.is_empty() {
				out += "::";
			}
			let local_name = DefaultElement::cpp_localname(self);
			let (first_letter, rest) = local_name.split_at(1);
			if self.as_field_setter().is_some() {
				out += &format!("setProp{}{}", first_letter.to_uppercase(), rest);
			} else {
				out += &format!("getProp{}{}", first_letter.to_uppercase(), rest);
			}
			out
		} else {
			self.cpp_fullname().into_owned()
		};
		out.cleanup_name();
		if let Some(spec) = self.as_specialized() {
			for typ in spec.values() {
				out.push('_');
				let mut typ = typ.to_string();
				typ.cleanup_name();
				out.push_str(&typ);
			}
		}
		if self.is_const() {
			out += "_const";
		}
		for arg in self.arguments() {
			out.push('_');
			let type_ref = arg.type_ref();
			out += &type_ref.cpp_safe_id();
		}
		out.into()
	}
}

impl<'tu> EntityElement<'tu> for Func<'tu> {
	fn entity(&self) -> Entity<'tu> {
		self.entity
	}
}

impl Element for Func<'_> {
	fn is_excluded(&self) -> bool {
		let identifier = self.identifier();
		if settings::FUNC_MANUAL.contains_key(identifier.as_ref()) || settings::FUNC_SPECIALIZE.contains_key(identifier.as_ref()) {
			return false;
		}
		DefaultElement::is_excluded(self)
			|| self.is_generic()
			|| if let Some(cls) = self.as_constructor() { // don't generate constructors of abstract classes
			cls.is_abstract()
		} else {
			false
		}
	}

	fn is_ignored(&self) -> bool {
		let identifier = self.identifier();
		if settings::FUNC_MANUAL.contains_key(identifier.as_ref()) || settings::FUNC_SPECIALIZE.contains_key(identifier.as_ref()) {
			return false;
		}
		DefaultElement::is_ignored(self)
			|| self.entity.get_availability() == Availability::Unavailable
			|| self.as_operator().map_or(false, |(.., op)| op == OperatorKind::Unsupported)
			|| self.arguments().into_iter().any(|a| a.type_ref().is_ignored())
			|| {
					let ret = self.return_type();
					ret.is_ignored() || ret.as_class().map_or(false, |cls| cls.is_abstract())
				}
			|| settings::FUNC_RENAME.get(identifier.as_ref()).filter(|&&n| n == "-").is_some()
	}

	fn is_system(&self) -> bool {
		DefaultElement::is_system(self)
	}

	fn is_public(&self) -> bool {
		DefaultElement::is_public(self)
	}

	fn usr(&self) -> Cow<str> {
		DefaultElement::usr(self)
	}

	fn rendered_doc_comment_with_prefix(&self, prefix: &str, opencv_version: &str) -> String {
		let mut comment = self.entity.get_comment().unwrap_or_default();
		const OVERLOAD: &str = "@overload";
		if let Some(idx) = comment.find(OVERLOAD) {
			let rep = if let Some(copy) = self.gen_env.get_func_comment(self.entity.cpp_fullname().as_ref()) {
				format!("{}\n\n## Overloaded parameters\n", copy)
			} else {
				"".to_string()
			};
			comment.replace_range(idx..idx + OVERLOAD.len(), &rep);
		}
		static COPY_BRIEF: Lazy<Regex> = Lazy::new(|| Regex::new(r#"@copybrief\s+(\w+)"#).unwrap());
		comment.replace_in_place_regex_cb(&COPY_BRIEF, |comment, caps| {
			let copy_name = caps.get(1).map(|(s, e)| &comment[s..e]).expect("Impossible");
			let mut copy_full_name = self.cpp_namespace().into_owned();
			copy_full_name += "::";
			copy_full_name += copy_name;
			if let Some(copy) = self.gen_env.get_func_comment(&copy_full_name) {
				Some(copy.into())
			} else {
				Some("".into())
			}
		});
		comment::render_doc_comment_with_processor(&comment, prefix, opencv_version, |out| {
			let mut default_args_comment = String::with_capacity(1024);
			for arg in self.arguments() {
				if let Some(def_val) = arg.default_value() {
					if default_args_comment.is_empty() {
						default_args_comment += "## C++ default parameters";
					}
					default_args_comment += &format!("\n* {name}: {val}", name=arg.rust_leafname(), val=def_val);
				}
			}
			if !default_args_comment.is_empty() {
				if !out.is_empty() {
					out.push_str("\n\n");
				}
				out.push_str(&default_args_comment);
			}
		})
	}

	fn cpp_namespace(&self) -> Cow<str> {
		DefaultElement::cpp_namespace(self)
	}

	fn cpp_localname(&self) -> Cow<str> {
		if self.as_conversion_method().is_some() {
			format!("operator {}", self.return_type().cpp_full()).into()
		} else if self.as_field_setter().is_some() {
			let name = DefaultElement::cpp_localname(self);
			let (first_letter, rest) = name.split_at(1);
			format!("set{}{}", first_letter.to_uppercase(), rest).into()
		} else {
			DefaultElement::cpp_localname(self)
		}
	}

	fn rust_module(&self) -> Cow<str> {
		DefaultElement::rust_module(self)
	}

	fn rust_leafname(&self) -> Cow<str> {
		let cpp_name = if let Some(name) = self.gen_env.get_export_config(self.entity).and_then(|c| c.rename.as_ref()) {
			name.into()
		} else {
			self.cpp_localname()
		};
		let rust_name = if let Some(cls) = self.as_constructor() {
			let args = self.arguments();
			#[allow(clippy::never_loop)] // fixme use named block when stable
			'ctor_name: loop {
				if args.is_empty() {
					break 'ctor_name "default";
				} else if args.len() == 1 {
					let arg_typeref = args[0].type_ref();
					let class_arg = arg_typeref.as_reference().and_then(|typ| {
						if let Some(ptr) = typ.as_smart_ptr() {
							ptr.pointee()
						} else {
							typ
						}.as_class()
					});
					if let Some(other) = class_arg {
						if cls == other {
							break 'ctor_name if arg_typeref.constness().is_const() {
								"copy"
							} else {
								"copy_mut"
							};
						}
					}
				}
				break 'ctor_name "new";
			}.into()
		} else if let Some(..) = self.as_conversion_method() {
			let mut name: String = self.return_type().rust_local().into_owned();
			name.cleanup_name();
			format!("to_{}", name).into()
		} else if let Some((.., kind)) = self.as_operator() {
			if cpp_name.starts_with("operator") {
				match kind {
					OperatorKind::Unsupported => {
						cpp_name
					}
					OperatorKind::Index => {
						if self.is_const() {
							"get".into()
						} else {
							"get_mut".into()
						}
					}
					OperatorKind::Add => {
						"add".into()
					}
					OperatorKind::Sub => {
						"sub".into()
					}
					OperatorKind::Mul => {
						"mul".into()
					}
					OperatorKind::Div => {
						"div".into()
					}
					OperatorKind::Deref => {
						if self.is_const() {
							"try_deref".into()
						} else {
							"try_deref_mut".into()
						}
					}
				}
			} else {
				cpp_name
			}
		} else {
			cpp_name
		};
		if let Some(&name) = settings::FUNC_RENAME.get(self.identifier().as_ref()) {
			if name.contains('+') {
				reserved_rename(name.replace('+', rust_name.as_ref()).to_snake_case().into())
			} else {
				name.into()
			}
		} else {
			reserved_rename(rust_name.to_snake_case().into())
		}
	}

	fn rust_localname(&self) -> Cow<str> {
		DefaultElement::rust_localname(self)
	}
}

impl fmt::Display for Func<'_> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		write!(f, "{}", self.entity.get_display_name().expect("Can't get display name"))
	}
}

impl fmt::Debug for Func<'_> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		let mut debug_struct = f.debug_struct("Func");
		self.update_debug_struct(&mut debug_struct)
			.field("export_config", &self.gen_env.get_export_config(self.entity))
			.field("is_const", &self.is_const())
			.field("type_hint", &self.type_hint)
			.field("kind", &self.kind())
			.field("return_type", &self.return_type())
			.field("arguments", &self.arguments())
			.finish()
	}
}