import Foundation
import UIKit

public func findTaggedComponentViewImpl(view: UIView, tag: Any) -> UIView? {
    if let view = view as? ComponentTaggedView {
        if view.matches(tag: tag) {
            return view
        }
    }
    
    for subview in view.subviews {
        if let result = findTaggedComponentViewImpl(view: subview, tag: tag) {
            return result
        }
    }
    
    return nil
}

public final class ComponentHostViewSkipSettingFrame {
    public init() {
    }
}

public final class ComponentHostView<EnvironmentType>: UIView {
    private var currentComponent: AnyComponent<EnvironmentType>?
    private var currentContainerSize: CGSize?
    private var currentSize: CGSize?
    public private(set) var componentView: UIView?
    private(set) var isUpdating: Bool = false
    
    public init() {
        super.init(frame: CGRect())
    }
    
    required public init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    public func update(transition: ComponentTransition, component: AnyComponent<EnvironmentType>, @EnvironmentBuilder environment: () -> Environment<EnvironmentType>, forceUpdate: Bool = false, containerSize: CGSize) -> CGSize {
        let size = self._update(transition: transition, component: component, maybeEnvironment: environment, updateEnvironment: true, forceUpdate: forceUpdate, containerSize: containerSize)
        self.currentSize = size
        return size
    }

    private func _update(transition: ComponentTransition, component: AnyComponent<EnvironmentType>, maybeEnvironment: () -> Environment<EnvironmentType>, updateEnvironment: Bool, forceUpdate: Bool, containerSize: CGSize) -> CGSize {
        precondition(!self.isUpdating)
        self.isUpdating = true

        precondition(containerSize.width.isFinite)
        precondition(containerSize.height.isFinite)
        
        let componentView: UIView
        if let current = self.componentView {
            componentView = current
        } else {
            componentView = component._makeView()
            self.componentView = componentView
            self.addSubview(componentView)
        }

        let context = componentView.context(component: component)

        let componentState: ComponentState = context.erasedState

        if updateEnvironment {
            EnvironmentBuilder._environment = context.erasedEnvironment
            let environmentResult = maybeEnvironment()
            EnvironmentBuilder._environment = nil
            context.erasedEnvironment = environmentResult
        }
        
        let isEnvironmentUpdated = context.erasedEnvironment.calculateIsUpdated()

        
        if !forceUpdate, !isEnvironmentUpdated, let currentComponent = self.currentComponent, let currentContainerSize = self.currentContainerSize, let currentSize = self.currentSize {
            if currentContainerSize == containerSize && currentComponent == component {
                self.isUpdating = false
                return currentSize
            }
        }
        self.currentComponent = component
        self.currentContainerSize = containerSize

        componentState._updated = { [weak self] transition, _ in
            guard let strongSelf = self else {
                return
            }
            let _ = strongSelf._update(transition: transition, component: component, maybeEnvironment: {
                preconditionFailure()
            } as () -> Environment<EnvironmentType>, updateEnvironment: false, forceUpdate: true, containerSize: containerSize)
        }

        let updatedSize = component._update(view: componentView, availableSize: containerSize, environment: context.erasedEnvironment, transition: transition)
        if transition.userData(ComponentHostViewSkipSettingFrame.self) == nil {
            transition.setFrame(view: componentView, frame: CGRect(origin: CGPoint(), size: updatedSize))
        }

        if isEnvironmentUpdated {
            context.erasedEnvironment._isUpdated = false
        }
        
        self.isUpdating = false

        return updatedSize
    }
    
    override public func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        if self.alpha.isZero {
            return nil
        }
        if !self.isUserInteractionEnabled {
            return nil
        }
        for view in self.subviews.reversed() {
            if view.isUserInteractionEnabled, view.alpha != 0.0, let result = view.hitTest(self.convert(point, to: view), with: event) {
                return result
            }
        }
        
        let result = super.hitTest(point, with: event)
        if result != self {
            return result
        } else {
            return nil
        }
    }
    
    public func findTaggedView(tag: Any) -> UIView? {
        guard let componentView = self.componentView else {
            return nil
        }
        
        return findTaggedComponentViewImpl(view: componentView, tag: tag)
    }
}

public final class ComponentView<EnvironmentType> {
    private var currentComponent: AnyComponent<EnvironmentType>?
    private var currentContainerSize: CGSize?
    private var currentSize: CGSize?
    public private(set) var view: UIView?
    private(set) var isUpdating: Bool = false
    public weak var parentState: ComponentState?
    
    public init() {
    }
    
    required public init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    public func update(transition: ComponentTransition, component: AnyComponent<EnvironmentType>, @EnvironmentBuilder environment: () -> Environment<EnvironmentType>, forceUpdate: Bool = false, containerSize: CGSize) -> CGSize {
        let size = self._update(transition: transition, component: component, maybeEnvironment: environment, updateEnvironment: true, forceUpdate: forceUpdate, containerSize: containerSize)
        self.currentSize = size
        return size
    }
    
    public func updateEnvironment(transition: ComponentTransition, @EnvironmentBuilder environment: () -> Environment<EnvironmentType>) -> CGSize? {
        guard let currentComponent = self.currentComponent, let currentContainerSize = self.currentContainerSize else {
            return nil
        }
        let size = self._update(transition: transition, component: currentComponent, maybeEnvironment: environment, updateEnvironment: true, forceUpdate: false, containerSize: currentContainerSize)
        self.currentSize = size
        return size
    }

    private func _update(transition: ComponentTransition, component: AnyComponent<EnvironmentType>, maybeEnvironment: () -> Environment<EnvironmentType>, updateEnvironment: Bool, forceUpdate: Bool, containerSize: CGSize) -> CGSize {
        precondition(!self.isUpdating)
        self.isUpdating = true

        precondition(containerSize.width.isFinite)
        precondition(containerSize.height.isFinite)
        
        let componentView: UIView
        if let current = self.view {
            componentView = current
        } else {
            componentView = component._makeView()
            self.view = componentView
        }

        let context = componentView.context(component: component)

        let componentState: ComponentState = context.erasedState

        if updateEnvironment {
            EnvironmentBuilder._environment = context.erasedEnvironment
            let environmentResult = maybeEnvironment()
            EnvironmentBuilder._environment = nil
            context.erasedEnvironment = environmentResult
        }
        
        var isStateUpdated = false
        if componentState.isUpdated {
            isStateUpdated = true
            componentState.isUpdated = false
        }
        
        let isEnvironmentUpdated = context.erasedEnvironment.calculateIsUpdated()
        
        if !forceUpdate, !isEnvironmentUpdated, !isStateUpdated, let currentComponent = self.currentComponent, let currentContainerSize = self.currentContainerSize, let currentSize = self.currentSize {
            if currentContainerSize == containerSize && currentComponent == component {
                self.isUpdating = false
                return currentSize
            }
        }
        self.currentComponent = component
        self.currentContainerSize = containerSize

        componentState._updated = { [weak self] transition, isLocal in
            guard let strongSelf = self else {
                return
            }
            if !isLocal, let parentState = strongSelf.parentState {
                parentState.updated(transition: transition)
            } else {
                let _ = strongSelf._update(transition: transition, component: component, maybeEnvironment: {
                    preconditionFailure()
                } as () -> Environment<EnvironmentType>, updateEnvironment: false, forceUpdate: true, containerSize: containerSize)
            }
        }

        let updatedSize = component._update(view: componentView, availableSize: containerSize, environment: context.erasedEnvironment, transition: transition)

        if isEnvironmentUpdated {
            context.erasedEnvironment._isUpdated = false
        }
        if isStateUpdated {
            context.erasedState.isUpdated = false
        }
        
        self.isUpdating = false

        return updatedSize
    }
    
    public func findTaggedView(tag: Any) -> UIView? {
        guard let view = self.view else {
            return nil
        }
        return findTaggedComponentViewImpl(view: view, tag: tag)
    }
}