import Foundation
import RemoteCore

public enum WristSide: String, Codable, Sendable { case left, right }
public enum CrownOrientation: String, Codable, Sendable { case towardHand, awayFromHand }

/// A normalized, user-relative sample. Values are dimensionless and bounded by
/// the motion adapter; this type intentionally contains no sensor or TV data.
public struct NormalizedMotionSample: Sendable, Equatable {
    public let timestamp: TimeInterval
    public let x: Double
    public let y: Double
    public let quality: Double

    public init(timestamp: TimeInterval, x: Double, y: Double, quality: Double = 1) {
        self.timestamp = timestamp; self.x = x; self.y = y; self.quality = quality
    }
}

public struct GestureRecognition: Sendable, Equatable {
    public let sessionID: UUID
    public let command: RemoteCommand
    public let confidence: Double
    public let timestamp: TimeInterval
}

public struct GestureRecognitionConfiguration: Sendable, Equatable {
    public var activationMagnitude: Double = 0.55
    public var neutralMagnitude: Double = 0.18
    public var minimumNeutralDwell: TimeInterval = 0.20
    public var candidateWindow: ClosedRange<TimeInterval> = 0.12...0.65
    public var cooldown: TimeInterval = 0.40
    public var stableNeutralDwell: TimeInterval = 0.20
    public var maximumSampleGap: TimeInterval = 0.12
    public var dominantAxisRatio: Double = 1.5
    public var minimumQuality: Double = 0.65

    public init() {}
}

/// A deterministic classifier over calibrated, user-relative samples. It is
/// deliberately conservative: mixed axes, poor quality, gaps and slow drift
/// produce no intent. One accepted excursion consumes readiness until a stable
/// neutral pose is observed after cooldown.
public struct CalibratedGestureRecognizer: Sendable {
    public let configuration: GestureRecognitionConfiguration
    public private(set) var sessionID: UUID?

    private var armedAt: TimeInterval?
    private var lastTimestamp: TimeInterval?
    private var neutralSince: TimeInterval?
    private var candidateStart: TimeInterval?
    private var candidatePeakX = 0.0
    private var candidatePeakY = 0.0
    private var candidateQuality = 1.0
    private var cooldownUntil: TimeInterval?
    private var waitingForNeutral = true

    public init(configuration: GestureRecognitionConfiguration = .init()) {
        self.configuration = configuration
    }

    public mutating func arm(sessionID: UUID, at timestamp: TimeInterval) {
        disarm()
        guard timestamp.isFinite else { return }
        self.sessionID = sessionID; armedAt = timestamp; lastTimestamp = nil
        waitingForNeutral = true
    }

    public mutating func disarm() {
        sessionID = nil; armedAt = nil; lastTimestamp = nil
        neutralSince = nil; candidateStart = nil; candidatePeakX = 0; candidatePeakY = 0
        candidateQuality = 1; cooldownUntil = nil; waitingForNeutral = true
    }

    public mutating func process(_ sample: NormalizedMotionSample) -> GestureRecognition? {
        guard let sessionID, let armedAt, sample.timestamp.isFinite,
              sample.timestamp >= armedAt,
              sample.x.isFinite, sample.y.isFinite,
              sample.quality.isFinite, sample.quality >= 0,
              sample.quality <= 1 else {
            resetCandidate(); waitingForNeutral = true; neutralSince = nil
            return nil
        }
        if let lastTimestamp, sample.timestamp <= lastTimestamp { return nil }
        if let lastTimestamp, sample.timestamp - lastTimestamp > configuration.maximumSampleGap {
            resetCandidate(); waitingForNeutral = true; neutralSince = nil
        }
        lastTimestamp = sample.timestamp
        let magnitude = hypot(sample.x, sample.y)
        guard magnitude <= 1.0 else { resetCandidate(); waitingForNeutral = true; return nil }

        if magnitude <= configuration.neutralMagnitude {
            if neutralSince == nil { neutralSince = sample.timestamp }
            if let cooldownUntil, sample.timestamp < cooldownUntil { return nil }
            if sample.timestamp - (neutralSince ?? sample.timestamp) >= configuration.stableNeutralDwell {
                waitingForNeutral = false; resetCandidate()
            }
            return nil
        }
        neutralSince = nil
        guard sample.quality >= configuration.minimumQuality else { resetCandidate(); waitingForNeutral = true; return nil }
        guard !waitingForNeutral else { return nil }

        if candidateStart == nil {
            guard magnitude >= configuration.neutralMagnitude else { return nil }
            candidateStart = sample.timestamp; candidatePeakX = sample.x; candidatePeakY = sample.y
            candidateQuality = sample.quality
            return nil
        }
        guard let start = candidateStart else { return nil }
        let duration = sample.timestamp - start
        guard duration <= configuration.candidateWindow.upperBound else { resetCandidate(); waitingForNeutral = true; return nil }
        candidatePeakX = abs(sample.x) > abs(candidatePeakX) ? sample.x : candidatePeakX
        candidatePeakY = abs(sample.y) > abs(candidatePeakY) ? sample.y : candidatePeakY
        candidateQuality = min(candidateQuality, sample.quality)
        let peakX = abs(candidatePeakX), peakY = abs(candidatePeakY)
        let peak = max(peakX, peakY)
        guard duration >= configuration.candidateWindow.lowerBound,
              peak >= configuration.activationMagnitude else { return nil }
        let dominant = max(peakX, peakY) / max(0.0001, min(peakX, peakY))
        guard dominant >= configuration.dominantAxisRatio else { resetCandidate(); waitingForNeutral = true; return nil }
        let command: RemoteCommand
        if peakX > peakY { command = candidatePeakX > 0 ? .right : .left }
        else { command = candidatePeakY > 0 ? .up : .down }
        let confidence = min(1, 0.5 * (peak / max(0.0001, configuration.activationMagnitude))
            + 0.3 * min(1, dominant / 3) + 0.2 * candidateQuality)
        resetCandidate(); waitingForNeutral = true; cooldownUntil = sample.timestamp + configuration.cooldown
        return GestureRecognition(sessionID: sessionID, command: command, confidence: confidence, timestamp: sample.timestamp)
    }

    private mutating func resetCandidate() {
        candidateStart = nil; candidatePeakX = 0; candidatePeakY = 0; candidateQuality = 1
    }
}