module NightLight.Core.Core

open System
open NightLight.Core.Models
open NightLight.Core.PartsOfDay
open NightLight.Core.ZigbeeEvents
open NightLight.Core.ZigbeeCommands
open NightLight.Core.Moods
open FsToolkit.ErrorHandling

let internal tryFindLight friendlyName =
    Seq.tryFind (fun light -> (lightProps light).FriendlyName = friendlyName) lights

let internal generateZigbeeCommandsToFixLight (light: Light) (desiredLightSettings: LightSettings) =
    seq {
        if desiredLightSettings.State = Off then
            yield generateStateCommand desiredLightSettings.State light

        if desiredLightSettings.State = On then
            yield generateBrightnessCommand light desiredLightSettings.Brightness
            yield generateColorCommand light desiredLightSettings.Color
    }

type internal NightLightState =
    { Time: DateTime
      Alarm: bool
      LightToManualState: Map<Light, State> }

let internal computeLightSettings (light: Light) (nightLightState: NightLightState) =
    let partOfDay = getPartOfDay nightLightState.Time

    let color, brightness =
        getDesiredMood (lightProps light).Room partOfDay
        |> getDesiredColorAndBrightness (lightProps light).Bulb

    { Color = color
      Brightness =
        if nightLightState.Alarm && (light = RightBedroomLamp || light = LeftBedroomLamp) then
            brightness.Scale(getAlarmWeight nightLightState.Time)
        else
            brightness
      State =
        if nightLightState.Alarm && (light = RightBedroomLamp || light = LeftBedroomLamp) then
            On
        else
            nightLightState.LightToManualState[light] }

let internal withStateFor (light: Light) (state: State) (oldNightLightState: NightLightState) =
    { oldNightLightState with
        LightToManualState = Map.add light state oldNightLightState.LightToManualState }

let internal withAlarmOff (oldNightLightState: NightLightState) =
    { oldNightLightState with
        Alarm = false }

let internal generateZigbeeCommandsForDifference (maybeBefore: NightLightState option) (after: NightLightState) =
    lights
    |> Seq.collect (fun light ->
        let oldLightSettings = maybeBefore |> Option.map (computeLightSettings light)
        let newLightSettings = after |> computeLightSettings light

        if oldLightSettings <> Some newLightSettings then
            generateZigbeeCommandsToFixLight light newLightSettings
        else
            Seq.empty)

type NightLightStateMachine private (maybeState: NightLightState option) =
    new() = NightLightStateMachine None

    member this.OnEventReceived(event: Event) : Result<NightLightStateMachine * Message seq, OnEventReceivedError> =
        result {
            match event, maybeState with
            | ReceivedZigbeeEvent payload, Some currentState ->
                let! zigbeeEvent = parseZigbeeEvent payload |> Result.mapError ParseZigbeeEventError

                return
                    match zigbeeEvent with
                    | DeviceAnnounce friendlyName ->
                        let maybeLight = tryFindLight friendlyName

                        this,
                        match maybeLight with
                        | Some light ->
                            currentState
                            |> computeLightSettings light
                            |> generateZigbeeCommandsToFixLight light
                        | None -> Seq.empty
                    | ButtonPress action ->
                        let newNightLightState =
                            match action with
                            | PressedOn ->
                                currentState
                                |> withAlarmOff
                                |> withStateFor RightBedroomLamp On
                                |> withStateFor LeftBedroomLamp On
                            | PressedOff ->
                                currentState
                                |> withAlarmOff
                                |> withStateFor RightBedroomLamp Off
                                |> withStateFor LeftBedroomLamp Off
                            | PressedLeft ->
                                currentState
                                |> withAlarmOff
                                |> withStateFor RightBedroomLamp Off
                                |> withStateFor LeftBedroomLamp On
                            | PressedRight ->
                                currentState
                                |> withStateFor LivingRoomWallLamp Off
                                |> withStateFor LivingRoomFloorLamp Off

                        NightLightStateMachine(Some newNightLightState),
                        generateZigbeeCommandsForDifference (Some currentState) newNightLightState
            | TimeChanged newTime, maybeCurrentState ->
                let alarm =
                    let newDayStarted =
                        let newPartOfDay = getPartOfDay newTime

                        let maybePreviousPartOfDay =
                            maybeCurrentState |> Option.map _.Time |> Option.map getPartOfDay

                        maybePreviousPartOfDay = Some Night && newPartOfDay = Day

                    newDayStarted
                    || maybeCurrentState |> Option.map _.Alarm |> Option.defaultValue false

                let newNightLightState =
                    { Time = newTime
                      Alarm = alarm
                      LightToManualState =
                        maybeCurrentState
                        |> Option.map _.LightToManualState
                        |> Option.defaultValue (lights |> Seq.map (fun light -> light, On) |> Map.ofSeq) }

                return
                    NightLightStateMachine(Some newNightLightState),
                    generateZigbeeCommandsForDifference maybeCurrentState newNightLightState
            | _, None -> return! Error TimeIsUnknown
        }