/**
 * Copyright (c) 2019-2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
 *
 * @author Fred Ludlow <fred.ludlow@gmail.com>
 * @author Alexander Rose <alexander.rose@weirdbyte.de>
 *
 * ported from NGL (https://github.com/arose/ngl), licensed under MIT
 */

import { Vec3, Tensor } from '../../mol-math/linear-algebra';
import { ParamDefinition as PD } from '../../mol-util/param-definition';
import { RuntimeContext } from '../../mol-task';
import { OrderedSet } from '../../mol-data/int';
import { PositionData } from './common';
import { Mat4 } from '../../mol-math/linear-algebra/3d';
import { Box3D, GridLookup3D, fillGridDim } from '../../mol-math/geometry';

function normalToLine (out: Vec3, p: Vec3) {
    out[0] = out[1] = out[2] = 1.0
    if (p[0] !== 0) {
        out[0] = (p[1] + p[2]) / -p[0]
    } else if (p[1] !== 0) {
        out[1] = (p[0] + p[2]) / -p[1]
    } else if (p[2] !== 0) {
        out[2] = (p[0] + p[1]) / -p[2]
    }
    return out
}

type AnglesTables = { cosTable: Float32Array, sinTable: Float32Array }
function getAngleTables (probePositions: number): AnglesTables {
    let theta = 0.0
    const step = 2 * Math.PI / probePositions

    const cosTable = new Float32Array(probePositions)
    const sinTable = new Float32Array(probePositions)
    for (let i = 0; i < probePositions; i++) {
        cosTable[i] = Math.cos(theta)
        sinTable[i] = Math.sin(theta)
        theta += step
    }
    return { cosTable, sinTable}
}

//

export const MolecularSurfaceCalculationParams = {
    resolution: PD.Numeric(0.5, { min: 0.01, max: 20, step: 0.01 }),
    probeRadius: PD.Numeric(1.4, { min: 0, max: 10, step: 0.1 }),
    probePositions: PD.Numeric(30, { min: 12, max: 90, step: 1 }),
}
export const DefaultMolecularSurfaceCalculationProps = PD.getDefaultValues(MolecularSurfaceCalculationParams)
export type MolecularSurfaceCalculationProps = typeof DefaultMolecularSurfaceCalculationProps


export async function calcMolecularSurface(ctx: RuntimeContext, position: Required<PositionData>, maxRadius: number, box: Box3D | null, props: MolecularSurfaceCalculationProps) {
    // Field generation method adapted from AstexViewer (Mike Hartshorn) by Fred Ludlow.
    // Other parts based heavily on NGL (Alexander Rose) EDT Surface class

    let lastClip = -1

    /**
     * Is the point at x,y,z obscured by any of the atoms specifeid by indices in neighbours.
     * Ignore indices a and b (these are the relevant atoms in projectPoints/Torii)
     *
     * Cache the last clipped atom (as very often the same one in subsequent calls)
     *
     * `a` and `b` must be resolved indices
     */
    function obscured(x: number, y: number, z: number, a: number, b: number) {
        if (lastClip !== -1) {
            const ai = lastClip
            if (ai !== a && ai !== b && singleAtomObscures(ai, x, y, z)) {
                return ai
            } else {
                lastClip = -1
            }
        }

        for (let j = 0, jl = neighbours.count; j < jl; ++j) {
            const ai = OrderedSet.getAt(indices, neighbours.indices[j])
            if (ai !== a && ai !== b && singleAtomObscures(ai, x, y, z)) {
                lastClip = ai
                return ai
            }
        }

        return -1
    }

    /**
     * `ai` must be a resolved index
     */
    function singleAtomObscures(ai: number, x: number, y: number, z: number) {
        const r = radius[ai]
        const dx = px[ai] - x
        const dy = py[ai] - y
        const dz = pz[ai] - z
        const dSq = dx * dx + dy * dy + dz * dz
        return dSq < (r * r)
    }

    /**
     * For each atom:
     *     Iterate over a subsection of the grid, for each point:
     *         If current value < 0.0, unvisited, set positive
     *
     *         In any case: Project this point onto surface of the atomic sphere
     *         If this projected point is not obscured by any other atom
     *             Calculate delta distance and set grid value to minimum of
     *             itself and delta
     */
    function projectPointsRange (begI: number, endI: number) {
        for (let i = begI; i < endI; ++i) {
            const j = OrderedSet.getAt(indices, i)
            const vx = px[j], vy = py[j], vz = pz[j]
            const rad = radius[j]
            const rSq = rad * rad

            lookup3d.find(vx, vy, vz, rad)

            // Number of grid points, round this up...
            const ng = Math.ceil(rad * scaleFactor)

            // Center of the atom, mapped to grid points (take floor)
            const iax = Math.floor(scaleFactor * (vx - minX))
            const iay = Math.floor(scaleFactor * (vy - minY))
            const iaz = Math.floor(scaleFactor * (vz - minZ))

            // Extents of grid to consider for this atom
            const begX = Math.max(0, iax - ng)
            const begY = Math.max(0, iay - ng)
            const begZ = Math.max(0, iaz - ng)

            // Add two to these points:
            // - iax are floor'd values so this ensures coverage
            // - these are loop limits (exclusive)
            const endX = Math.min(dimX, iax + ng + 2)
            const endY = Math.min(dimY, iay + ng + 2)
            const endZ = Math.min(dimZ, iaz + ng + 2)

            for (let xi = begX; xi < endX; ++xi) {
                const dx = gridx[xi] - vx
                const xIdx = xi * iuv
                for (let yi = begY; yi < endY; ++yi) {
                    const dy = gridy[yi] - vy
                    const dxySq = dx * dx + dy * dy
                    const xyIdx = yi * iu + xIdx
                    for (let zi = begZ; zi < endZ; ++zi) {
                        const dz = gridz[zi] - vz
                        const dSq = dxySq + dz * dz

                        if (dSq < rSq) {
                            const idx = zi + xyIdx

                            // if unvisited, make positive
                            if (data[idx] < 0.0) data[idx] *= -1

                            // Project on to the surface of the sphere
                            // sp is the projected point ( dx, dy, dz ) * ( ra / d )
                            const d = Math.sqrt(dSq)
                            const ap = rad / d
                            const spx = dx * ap + vx
                            const spy = dy * ap + vy
                            const spz = dz * ap + vz

                            if (obscured(spx, spy, spz, j, -1) === -1) {
                                const dd = rad - d
                                if (dd < data[idx]) {
                                    data[idx] = dd
                                    idData[idx] = id[i]
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    async function projectPoints() {
        for (let i = 0; i < n; i += updateChunk) {
            projectPointsRange(i, Math.min(i + updateChunk, n))

            if (ctx.shouldUpdate) {
                await ctx.update({ message: 'projecting points', current: i, max: n })
            }
        }
    }

    // Vectors for Torus Projection
    const atob = Vec3()
    const mid = Vec3()
    const n1 = Vec3()
    const n2 = Vec3()
    /**
     * `a` and `b` must be resolved indices
     */
    function projectTorus(a: number, b: number) {
        const rA = radius[a]
        const rB = radius[b]
        const dx = atob[0] = px[b] - px[a]
        const dy = atob[1] = py[b] - py[a]
        const dz = atob[2] = pz[b] - pz[a]
        const dSq = dx * dx + dy * dy + dz * dz

        // This check now redundant as already done in AVHash.withinRadii
        // if (dSq > ((rA + rB) * (rA + rB))) { return }

        const d = Math.sqrt(dSq)

        // Find angle between a->b vector and the circle
        // of their intersection by cosine rule
        const cosA = (rA * rA + d * d - rB * rB) / (2.0 * rA * d)

        // distance along a->b at intersection
        const dmp = rA * cosA

        Vec3.normalize(atob, atob)

        // Create normal to line
        normalToLine(n1, atob)
        Vec3.normalize(n1, n1)

        // Cross together for second normal vector
        Vec3.cross(n2, atob, n1)
        Vec3.normalize(n2, n2)

        // r is radius of circle of intersection
        const rInt = Math.sqrt(rA * rA - dmp * dmp)

        Vec3.scale(n1, n1, rInt)
        Vec3.scale(n2, n2, rInt)
        Vec3.scale(atob, atob, dmp)

        mid[0] = atob[0] + px[a]
        mid[1] = atob[1] + py[a]
        mid[2] = atob[2] + pz[a]

        lastClip = -1

        for (let i = 0; i < probePositions; ++i) {
            const cost = cosTable[i]
            const sint = sinTable[i]

            const px = mid[0] + cost * n1[0] + sint * n2[0]
            const py = mid[1] + cost * n1[1] + sint * n2[1]
            const pz = mid[2] + cost * n1[2] + sint * n2[2]

            if (obscured(px, py, pz, a, b) === -1) {
                const iax = Math.floor(scaleFactor * (px - minX))
                const iay = Math.floor(scaleFactor * (py - minY))
                const iaz = Math.floor(scaleFactor * (pz - minZ))

                const begX = Math.max(0, iax - ngTorus)
                const begY = Math.max(0, iay - ngTorus)
                const begZ = Math.max(0, iaz - ngTorus)

                const endX = Math.min(dimX, iax + ngTorus + 2)
                const endY = Math.min(dimY, iay + ngTorus + 2)
                const endZ = Math.min(dimZ, iaz + ngTorus + 2)

                for (let xi = begX; xi < endX; ++xi) {
                    const dx = px - gridx[xi]
                    const xIdx = xi * iuv

                    for (let yi = begY; yi < endY; ++yi) {
                        const dy = py - gridy[yi]
                        const dxySq = dx * dx + dy * dy
                        const xyIdx = yi * iu + xIdx

                        for (let zi = begZ; zi < endZ; ++zi) {
                            const dz = pz - gridz[zi]
                            const dSq = dxySq + dz * dz

                            const idx = zi + xyIdx
                            const current = data[idx]

                            if (current > 0.0 && dSq < (current * current)) {
                                data[idx] = Math.sqrt(dSq)
                                // Is this grid point closer to a or b?
                                // Take dot product of atob and gridpoint->p (dx, dy, dz)
                                const dp = dx * atob[0] + dy * atob[1] + dz * atob[2]
                                idData[idx] = id[OrderedSet.indexOf(indices, dp < 0.0 ? b : a)]
                            }
                        }
                    }
                }
            }
        }
    }

    function projectToriiRange (begI: number, endI: number) {
        for (let i = begI; i < endI; ++i) {
            const k = OrderedSet.getAt(indices, i)
            lookup3d.find(px[k], py[k], pz[k], radius[k])
            for (let j = 0, jl = neighbours.count; j < jl; ++j) {
                const l = OrderedSet.getAt(indices, neighbours.indices[j])
                if (k < l) projectTorus(k, l)
            }
        }
    }

    async function projectTorii() {
        for (let i = 0; i < n; i += updateChunk) {
            projectToriiRange(i, Math.min(i + updateChunk, n))

            if (ctx.shouldUpdate) {
                await ctx.update({ message: 'projecting torii', current: i, max: n })
            }
        }
    }

    // console.time('MolecularSurface')
    // console.time('MolecularSurface createState')
    const { resolution, probeRadius, probePositions } = props
    const scaleFactor = 1 / resolution
    const ngTorus = Math.max(5, 2 + Math.floor(probeRadius * scaleFactor))

    const cellSize = Vec3.create(maxRadius, maxRadius, maxRadius)
    Vec3.scale(cellSize, cellSize, 2)
    const lookup3d = GridLookup3D(position, cellSize)
    const neighbours = lookup3d.result
    if (box === null) box = lookup3d.boundary.box

    const { indices, x: px, y: py, z: pz, id, radius } = position
    const n = OrderedSet.size(indices)

    const pad = maxRadius + resolution
    const expandedBox = Box3D.expand(Box3D(), box, Vec3.create(pad, pad, pad));
    const [ minX, minY, minZ ] = expandedBox.min
    const scaledBox = Box3D.scale(Box3D(), expandedBox, scaleFactor)
    const dim = Box3D.size(Vec3(), scaledBox)
    Vec3.ceil(dim, dim)

    const [ dimX, dimY, dimZ ] = dim
    const iu = dimZ, iv = dimY, iuv = iu * iv

    const { cosTable, sinTable } = getAngleTables(probePositions)

    const space = Tensor.Space(dim, [0, 1, 2], Float32Array)
    const data = space.create()
    const idData = space.create()

    data.fill(-1001.0)
    idData.fill(-1)

    const gridx = fillGridDim(dimX, minX, resolution)
    const gridy = fillGridDim(dimY, minY, resolution)
    const gridz = fillGridDim(dimZ, minZ, resolution)

    const updateChunk = Math.ceil(100000 / ((Math.pow(Math.pow(maxRadius, 3), 3) * scaleFactor)))
    // console.timeEnd('MolecularSurface createState')

    // console.time('MolecularSurface projectPoints')
    await projectPoints()
    // console.timeEnd('MolecularSurface projectPoints')

    // console.time('MolecularSurface projectTorii')
    await projectTorii()
    // console.timeEnd('MolecularSurface projectTorii')
    // console.timeEnd('MolecularSurface')

    const field = Tensor.create(space, data)
    const idField = Tensor.create(space, idData)

    const transform = Mat4.identity()
    Mat4.fromScaling(transform, Vec3.create(resolution, resolution, resolution))
    Mat4.setTranslation(transform, expandedBox.min)
    // console.log({ field, idField, transform, updateChunk })
    return { field, idField, transform }
}