//
// Swiftfin is subject to the terms of the Mozilla Public
// License, v2.0. If a copy of the MPL was not distributed with this
// file, you can obtain one at https://mozilla.org/MPL/2.0/.
//
// Copyright (c) 2022 Jellyfin & Jellyfin Contributors
//

import Foundation

public extension BlurHash {
    var string: String {
        let flatComponents = components.reduce([]) { $0 + $1 }
        let dc = flatComponents.first!
        let ac = flatComponents.dropFirst()

        var hash = ""

        let sizeFlag = (numberOfHorizontalComponents - 1) + (numberOfVerticalComponents - 1) * 9
        hash += sizeFlag.encode83(length: 1)

        let maximumValue: Float
        if !ac.isEmpty {
            let actualMaximumValue = ac.map { max(abs($0.0), abs($0.1), abs($0.2)) }.max()!
            let quantisedMaximumValue = Int(max(0, min(82, floor(actualMaximumValue * 166 - 0.5))))
            maximumValue = Float(quantisedMaximumValue + 1) / 166
            hash += quantisedMaximumValue.encode83(length: 1)
        } else {
            maximumValue = 1
            hash += 0.encode83(length: 1)
        }

        hash += encodeDC(dc).encode83(length: 4)

        for factor in ac {
            hash += encodeAC(factor, maximumValue: maximumValue).encode83(length: 2)
        }

        return hash
    }

    private func encodeDC(_ value: (Float, Float, Float)) -> Int {
        let roundedR = linearTosRGB(value.0)
        let roundedG = linearTosRGB(value.1)
        let roundedB = linearTosRGB(value.2)
        return (roundedR << 16) + (roundedG << 8) + roundedB
    }

    private func encodeAC(_ value: (Float, Float, Float), maximumValue: Float) -> Int {
        let quantR = Int(max(0, min(18, floor(signPow(value.0 / maximumValue, 0.5) * 9 + 9.5))))
        let quantG = Int(max(0, min(18, floor(signPow(value.1 / maximumValue, 0.5) * 9 + 9.5))))
        let quantB = Int(max(0, min(18, floor(signPow(value.2 / maximumValue, 0.5) * 9 + 9.5))))

        return quantR * 19 * 19 + quantG * 19 + quantB
    }
}