// Package di provides dependency injection for the Iris Hero and Iris MVC new features.
// It's used internally by "hero" and "mvc" packages.
package di

import (
	"reflect"

	"github.com/kataras/iris/v12/context"
)

type (
	// Hijacker is a type which is used to catch fields or function's input argument
	// to bind a custom object based on their type.
	Hijacker func(reflect.Type) (*BindObject, bool)
	// TypeChecker checks if a specific field's or function input argument's
	// is valid to be binded.
	TypeChecker func(reflect.Type) bool
	// ErrorHandler is the optional interface to handle errors per hero func,
	// see `mvc/Application#HandleError` for MVC application-level error handler registration too.
	//
	// Handles non-nil errors return from a hero handler or a controller's method (see `DispatchFuncResult`)
	// and (from v12.1.8) the error may return from a request-scoped dynamic dependency (see `MakeReturnValue`).
	ErrorHandler interface {
		HandleError(ctx context.Context, err error)
	}

	// ErrorHandlerFunc implements the `ErrorHandler`.
	// It describes the type defnition for an error handler.
	ErrorHandlerFunc func(ctx context.Context, err error)
)

// HandleError fires when the `DispatchFuncResult` or `MakereturnValue` return a non-nil error.
func (fn ErrorHandlerFunc) HandleError(ctx context.Context, err error) {
	fn(ctx, err)
}

var (
	// DefaultHijacker is the hijacker used on the package-level Struct & Func functions.
	DefaultHijacker Hijacker
	// DefaultTypeChecker is the typechecker used on the package-level Struct & Func functions.
	DefaultTypeChecker TypeChecker
	// DefaultErrorHandler is the error handler used on the package-level `Func` function
	// to catch any errors from dependencies or handlers.
	DefaultErrorHandler ErrorHandler
)

// Struct is being used to return a new injector based on
// a struct value instance, if it contains fields that the types of those
// are matching with one or more of the `Values` then they are binded
// with the injector's `Inject` and `InjectElem` methods.
func Struct(s interface{}, values ...reflect.Value) *StructInjector {
	if s == nil {
		return &StructInjector{}
	}

	return MakeStructInjector(
		ValueOf(s),
		DefaultHijacker,
		DefaultTypeChecker,
		SortByNumMethods,
		Values(values).CloneWithFieldsOf(s)...,
	)
}

// Func is being used to return a new injector based on
// a function, if it contains input arguments that the types of those
// are matching with one or more of the `Values` then they are binded
// to the function's input argument when called
// with the injector's `Inject` method.
func Func(fn interface{}, values ...reflect.Value) *FuncInjector {
	if fn == nil {
		return &FuncInjector{}
	}

	return MakeFuncInjector(
		ValueOf(fn),
		DefaultHijacker,
		DefaultTypeChecker,
		DefaultErrorHandler,
		values...,
	)
}

// D is the Dependency Injection container,
// it contains the Values that can be changed before the injectors.
// `Struct` and the `Func` methods returns an injector for specific
// struct instance-value or function.
type D struct {
	Values

	hijacker     Hijacker
	goodFunc     TypeChecker
	errorHandler ErrorHandler
	sorter       Sorter
}

// New creates and returns a new Dependency Injection container.
// See `Values` field and `Func` and `Struct` methods for more.
func New() *D {
	return &D{}
}

// Hijack sets a hijacker function, read the `Hijacker` type for more explanation.
func (d *D) Hijack(fn Hijacker) *D {
	d.hijacker = fn
	return d
}

// GoodFunc sets a type checker for a valid function that can be binded,
// read the `TypeChecker` type for more explanation.
func (d *D) GoodFunc(fn TypeChecker) *D {
	d.goodFunc = fn
	return d
}

// ErrorHandler adds a handler which will be fired when a handler's second output argument is error and it's not nil
// or when a request-scoped dynamic function dependency's second output argument is error and it's not nil.
func (d *D) ErrorHandler(errorHandler ErrorHandler) *D {
	d.errorHandler = errorHandler
	return d
}

// Sort sets the fields and valid bindable values sorter for struct injection.
func (d *D) Sort(with Sorter) *D {
	d.sorter = with
	return d
}

// Clone returns a new Dependency Injection container, it adopts the
// parent's (current "D") hijacker, good func type checker, sorter and all dependencies values.
func (d *D) Clone() *D {
	return &D{
		Values:       d.Values.Clone(),
		hijacker:     d.hijacker,
		goodFunc:     d.goodFunc,
		errorHandler: d.errorHandler,
		sorter:       d.sorter,
	}
}

// Struct is being used to return a new injector based on
// a struct value instance, if it contains fields that the types of those
// are matching with one or more of the `Values` then they are binded
// with the injector's `Inject` and `InjectElem` methods.
func (d *D) Struct(s interface{}) *StructInjector {
	if s == nil {
		return &StructInjector{Has: false}
	}

	return MakeStructInjector(
		ValueOf(s),
		d.hijacker,
		d.goodFunc,
		d.sorter,
		d.Values.CloneWithFieldsOf(s)...,
	)
}

// Func is being used to return a new injector based on
// a function, if it contains input arguments that the types of those
// are matching with one or more of the `Values` then they are binded
// to the function's input argument when called
// with the injector's `Inject` method.
func (d *D) Func(fn interface{}) *FuncInjector {
	if fn == nil {
		return &FuncInjector{Has: false}
	}

	return MakeFuncInjector(
		ValueOf(fn),
		d.hijacker,
		d.goodFunc,
		d.errorHandler,
		d.Values...,
	).ErrorHandler(d.errorHandler)
}