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package io.data2viz.shape

import kotlin.math.abs
import kotlin.math.max
import kotlin.math.min


// TODO rename PieLayout ?
fun  pie(init: PieGenerator.() -> Unit) = PieGenerator().apply(init)
class PieGenerator {

    var value: (D) -> Double = const(.0)
    var startAngle: (Array) -> Double = const(.0)
    var endAngle: (Array) -> Double = const(tau)
    var padAngle: (Array) -> Double = const(.0)

    /**
     * Use the data to generate a line on the path
     */
    fun render(data: Array): Array> {
        val n = data.size
        var sum = .0
        val index: Array = Array(n, { 0 })
        val arcs: Array> = Array(n, { ArcParams(.0, .0, .0, null, null, null) })
        val values: Array = Array(n, { .0})
        var a0 = startAngle(data)
        val da = min(tau, max(-tau, endAngle(data) - a0))
        val p =  min(abs(da) / n, padAngle(data)) //  min(abs(da) / n, .0)
        val pa = if (da < .0) -p else p

        for (i in 0 until n) {
            index[i] = i
            val v = value(data[i])
            values[i] = v
            if (v > 0) sum += v
        }

        // TODO : sorting
        // Optionally sort the arcs by previously-computed values or by data.
        //if (sortValues != null) index.sort(function(i, j) { return sortValues(arcs[i], arcs[j]); });
        //else if (sort != null) index.sort(function(i, j) { return sort(data[i], data[j]); });

        // Compute the arcs! They are stored in the original data's order.
        val k = if (sum > .0) ((da - n * pa) / sum) else .0
        for (i in 0 until n) {
            val j = index[i]
            val v = values[j]
            val a1 = a0 + (if (v > .0) (v * k) else .0) + pa
            arcs[j] = ArcParams(a0, a1, p, v,i, data[j])
            a0 = a1
        }

        return arcs
    }
}