/**
 * Copyright (c) 2018-2022 mol* contributors, licensed under MIT, See LICENSE file for more info.
 *
 * @author Michal Malý <michal.maly@ibt.cas.cz>
 * @author Jiří Černý <jiri.cerny@ibt.cas.cz>
 */

import { NtCTubeTypes as NTT } from './types';
import { NtCTubeProvider } from './property';
import { DnatcoUtil } from '../util';
import { Segmentation, SortedArray } from '../../../mol-data/int';
import { Vec3 } from '../../../mol-math/linear-algebra';
import { ChainIndex, ElementIndex, ResidueIndex, Structure, StructureElement, Unit } from '../../../mol-model/structure';

function getAtomPosition(vec: Vec3, loc: StructureElement.Location, residue: DnatcoUtil.Residue, names: string[], altId: string, insCode: string) {
    const eI = DnatcoUtil.getAtomIndex(loc, residue, names, altId, insCode);
    if (eI !== -1) {
        loc.unit.conformation.invariantPosition(eI, vec);
        return true;
    }

    return false; // Atom not found
}

const p_1 = Vec3();
const p0 = Vec3();
const p1 = Vec3();
const p2 = Vec3();
const p3 = Vec3();
const p4 = Vec3();
const pP = Vec3();

const C5PrimeNames = ['C5\'', 'C5*'];
const O3PrimeNames = ['O3\'', 'O3*'];
const O5PrimeNames = ['O5\'', 'O5*'];
const PNames = ['P'];

function getPoints(
    loc: StructureElement.Location,
    r0: DnatcoUtil.Residue | undefined, r1: DnatcoUtil.Residue, r2: DnatcoUtil.Residue,
    altId0: string, altId1: string, altId2: string,
    insCode0: string, insCode1: string, insCode2: string,
) {
    if (r0) {
        if (!getAtomPosition(p_1, loc, r0, C5PrimeNames, altId0, insCode0))
            return void 0;
        if (!getAtomPosition(p0, loc, r0, O3PrimeNames, altId0, insCode0))
            return void 0;
    } else {
        if (!getAtomPosition(p0, loc, r1, O5PrimeNames, altId1, insCode1))
            return void 0;
    }

    if (!getAtomPosition(p1, loc, r1, C5PrimeNames, altId1, insCode1))
        return void 0;
    if (!getAtomPosition(p2, loc, r1, O3PrimeNames, altId1, insCode1))
        return void 0;

    if (!getAtomPosition(p3, loc, r2, C5PrimeNames, altId2, insCode2))
        return void 0;
    if (!getAtomPosition(p4, loc, r2, O3PrimeNames, altId2, insCode2))
        return void 0;
    if (!getAtomPosition(pP, loc, r2, PNames, altId2, insCode2))
        return void 0;

    return { p_1, p0, p1, p2, p3, p4, pP };
}

function hasGapElements(r: DnatcoUtil.Residue, unit: Unit) {
    for (let xI = r.start; xI < r.end; xI++) {
        const eI = unit.elements[xI];
        if (SortedArray.has(unit.gapElements, eI)) {
            return true;
        }
    }

    return false;
}

export type NtCTubeSegment = {
    p_1: Vec3,
    p0: Vec3,
    p1: Vec3,
    p2: Vec3,
    p3: Vec3,
    p4: Vec3,
    pP: Vec3,
    stepIdx: number,
    followsGap: boolean,
    firstInChain: boolean,
    capEnd: boolean,
}

export class NtCTubeSegmentsIterator {
    private chainIt: Segmentation.SegmentIterator<ChainIndex>;
    private residueIt: Segmentation.SegmentIterator<ResidueIndex>;

    /* Second residue of the previous step, may be undefined
     * if we are at the beginning of a chain or right after a discontinuity */
    private residuePrev?: DnatcoUtil.Residue;
    /* First residue of the current step */
    private residueOne?: DnatcoUtil.Residue;
    /* Second residue of the current step */
    private residueTwo: DnatcoUtil.Residue;
    /* First residue of the next step, may be undefined
     * if we are at the end of a chain.
     * Undefined value indicates that the iterator has reached the end.*/
    private residueNext?: DnatcoUtil.Residue;

    private data?: NTT.Data;
    private altIdOne = '';
    private insCodeOne = '';
    private loc: StructureElement.Location;

    private moveStep() {
        if (!this.residueNext)
            return void 0;

        /* Assume discontinuity of the ResidueIndex of the residue that would become residue one (= first residue of the corresponding step)
         * does not equal to ResidueIndex of what would be residue two (= second residue of the corresponding step). */
        if (this.residueTwo.index + 1 === this.residueNext.index) {
            this.residuePrev = DnatcoUtil.copyResidue(this.residueOne);
            this.residueOne = DnatcoUtil.copyResidue(this.residueTwo);
            this.residueTwo = DnatcoUtil.copyResidue(this.residueNext)!;
            this.residueNext = this.residueIt.hasNext ? DnatcoUtil.copyResidue(this.residueIt.move())! : void 0;
        } else {
            if (!this.residueIt.hasNext) {
                this.residueNext = void 0;
                return void 0;
            }

            // There is discontinuity, act as if we were at the beginning of a chain
            this.residuePrev = void 0;
            this.residueOne = DnatcoUtil.copyResidue(this.residueNext);
            this.residueTwo = DnatcoUtil.copyResidue(this.residueIt.move())!;
            this.residueNext = this.residueIt.hasNext ? DnatcoUtil.copyResidue(this.residueIt.move())! : void 0;
        }

        return this.toSegment(this.residuePrev, this.residueOne!, this.residueTwo, this.residueNext);
    }

    private prime() {
        if (this.residueIt.hasNext)
            this.residueTwo = DnatcoUtil.copyResidue(this.residueIt.move())!;
        if (this.residueIt.hasNext)
            this.residueNext = this.residueIt.move();
    }

    private toSegment(r0: DnatcoUtil.Residue | undefined, r1: DnatcoUtil.Residue, r2: DnatcoUtil.Residue, r3: DnatcoUtil.Residue | undefined): NtCTubeSegment | undefined {
        const indices = DnatcoUtil.getStepIndices(this.data!.data, this.loc, r1);
        if (indices.length === 0)
            return void 0;

        const stepIdx = indices[0];
        const step = this.data!.data.steps[stepIdx];

        const altIdPrev = this.altIdOne;
        const insCodePrev = this.insCodeOne;
        this.altIdOne = step.label_alt_id_1;
        this.insCodeOne = step.PDB_ins_code_1;
        const altIdTwo = step.label_alt_id_2;
        const insCodeTwo = step.PDB_ins_code_2;
        const followsGap = !!r0 && hasGapElements(r0, this.loc.unit) && hasGapElements(r1, this.loc.unit);
        const precedesDiscontinuity = r3 ? r3.index !== r2.index + 1 : false;
        const points = getPoints(this.loc, r0, r1, r2, altIdPrev, this.altIdOne, altIdTwo, insCodePrev, this.insCodeOne, insCodeTwo);
        if (!points)
            return void 0;

        return {
            ...points,
            stepIdx,
            followsGap,
            firstInChain: !r0,
            capEnd: !this.residueNext || precedesDiscontinuity || hasGapElements(r2, this.loc.unit),
        };
    }

    constructor(structure: Structure, unit: Unit.Atomic) {
        this.chainIt = Segmentation.transientSegments(unit.model.atomicHierarchy.chainAtomSegments, unit.elements);
        this.residueIt = Segmentation.transientSegments(unit.model.atomicHierarchy.residueAtomSegments, unit.elements);

        const prop = NtCTubeProvider.get(unit.model).value;
        this.data = prop?.data;

        if (this.chainIt.hasNext) {
            this.residueIt.setSegment(this.chainIt.move());
            this.prime();
        }

        this.loc = StructureElement.Location.create(structure, unit, -1 as ElementIndex);
    }

    get hasNext() {
        if (!this.data)
            return false;
        return !!this.residueNext
            ? true
            : this.chainIt.hasNext;
    }

    move() {
        if (!!this.residueNext) {
            return this.moveStep();
        } else {
            this.residuePrev = void 0; // Assume discontinuity when we switch chains
            this.residueNext = void 0;

            this.residueIt.setSegment(this.chainIt.move());
            this.prime();

            return this.moveStep();
        }
    }
}