import { makeFace } from 'wmc-common/geometry';

import * as linalg from './linalg';
import { loadObjModel } from './obj';
import * as se3 from 'wmc-common/se3';
import { computeOrbit, findSoi, getCartesianState, updateBodyPhysics, isInSoi } from './orbit';
import { getBodyGeometry, castRay, BlockType } from './chunk';
import { draw, getOrbitDrawContext, initWorldGl } from './draw';
import * as quat from './quat';

const kEpoch = 0;

function closeToPlanet(context) {
    const body = findSoi(context.universe, context.player.position);
    const relativePos = linalg.diff(context.player.position, body.position);

    return linalg.norm(relativePos) < 20;
}

function getSolarSystem(seed: number) {
    /// XXX: only returns 1 body for now

    return {
        name: 'Tat',

        mass: 1000.0,
        spin: [0, 0, 0.2],

        geometry: getBodyGeometry(0),
        glowColor: [0.5, 0.5, 0.46],

        children: [
            {
                name: 'Quicksilver',
                seed: 1336,

                mass: 0.1,
                spin: [0.0, 0.0, 0.05],

                geometry: makeCube([0, 4]),

                orbit: {
                    excentricity: 0.0,
                    semimajorAxis: 200,
                    inclination: 0.8,
                    ascendingNodeLongitude: 0,
                    periapsisArgument: 0,
                    t0: 0,
                },
            },
            {
                name: 'Satourne',
                seed: 1338,

                mass: 0.1,
                spin: [0.0, 0.5, 0.0],

                geometry: makeCube([0, 5]),

                orbit: {
                    excentricity: 0.0,
                    semimajorAxis: 900,
                    inclination: 0.0,
                    ascendingNodeLongitude: 0,
                    periapsisArgument: 0,
                    t0: 0,
                },

                children: [
                    {
                        name: 'Kyoujin',
                        seed: 13381,

                        mass: 0.01,
                        spin: [0.0, 0.0, 0.05],

                        geometry: makeCube([0, 6]),

                        orbit: {
                            excentricity: 0.0,
                            semimajorAxis: 20,
                            inclination: Math.PI / 2,
                            ascendingNodeLongitude: 0,
                            periapsisArgument: 0,
                            t0: 0,
                        },
                    },
                ],
            },
            {
                name: 'Tataooine',
                seed: 1337,

                mass: 50,
                spin: [0.0, 0.0, 0.05],

                geometry: getBodyGeometry(1337),

                orbit: {
                    excentricity: 0.3,
                    semimajorAxis: 500,
                    inclination: 0.0,
                    ascendingNodeLongitude: 0,
                    periapsisArgument: 0,
                    t0: 0,
                },

                children: [
                    {
                        name: 'Mun',
                        seed: 13371,

                        mass: 0.01,
                        spin: [0.0, 0.0, 0.05],

                        geometry: makeCube([0, 7]),

                        orbit: {
                            excentricity: 0.0,
                            semimajorAxis: 50,
                            inclination: Math.PI / 2,
                            ascendingNodeLongitude: 0,
                            periapsisArgument: 0,
                            t0: 0,
                        },
                    },
                ],
            },
        ],
    };
}

function initUiListeners(canvas: HTMLCanvasElement, context) {
    const canvasClickHandler = () => {
        canvas.requestPointerLock();
        canvas.onclick = null;
//        const clickListener = e => {
//            switch(e.button) {
//                case 0:  // left click
//                    destroySelectedBlock(context);
//                    break;
//                case 2:  // right click
//                    makeDirBlock(context);
//                    break;
//            }
//        };
        const clickListener = e => {};
        const keyListener = e => {
            if (e.type === 'keydown') {
                if (e.repeat) return;
                context.keys.add(e.code);

                switch (e.code) {
                    case 'KeyF':
                        context.flying = !context.flying;
                        context.player.velocity = [0, 0, 0];
                        delete context.orbit;
                        return false;
                    case 'KeyL':
                        context.landing = !context.landing;
                        return false;
                    case 'Space':
                        context.pause = !context.pause;
                        return false;
                }
            } else {
                context.keys.delete(e.code);
            }
        };
        const moveListener = e => {
//            context.camera.orientation[0] -= e.movementY / 500;
//            context.camera.orientation[1] -= e.movementX / 500;
            context.camera.tf =[
                context.camera.tf,
                se3.roty(-e.movementX / 500),
                se3.rotx(-e.movementY / 500),
            ].reduce(se3.product);
        };
        const changeListener = () => {
            if (document.pointerLockElement === canvas) {
                return;
            }
            document.removeEventListener('pointerdown', clickListener);
            document.removeEventListener('pointerlockchange', changeListener);
            document.removeEventListener('pointermove', moveListener);
            document.removeEventListener('keydown', keyListener);
            document.removeEventListener('keyup', keyListener);
            canvas.onclick = canvasClickHandler;
        };
        document.addEventListener('pointerdown', clickListener);
        document.addEventListener('pointerlockchange', changeListener);
        document.addEventListener('pointermove', moveListener);
        document.addEventListener('keydown', keyListener);
        document.addEventListener('keyup', keyListener);
    };
    canvas.onclick = canvasClickHandler;
    document.addEventListener('keydown', e => {
        if (e.repeat) return;
        switch (e.code) {
            case 'F11':
                canvas.requestFullscreen();
                break;
        }
    });
}

function handleInput(context) {
    const move = (forward: number, right: number) => {
        if (context.keys.has('ShiftLeft')) {
            forward *= 10;
            right *= 10;
        }
        const tf = se3.product(
            se3.orientationOnly(context.player.tf),
            context.camera.tf,
        );
        const dir = [right, 0, -forward, 10];
        if (context.flying) {
            context.player.tf = [
                context.player.tf,
                se3.translation(...dir),
            ].reduce(se3.product);
        } else {
            const vel = context.player.velocity;
            const dv = linalg.scale(se3.apply(tf, dir), 1/dir[3]);
            context.player.velocity = linalg.add(vel, dv);
            delete context.orbit;
        }
    };

    const roll = (amount: number) => {
        if (context.keys.has('ShiftLeft')) {
            amount *= 10;
        }
        context.camera.tf =[
            context.camera.tf,
            se3.rotz(amount),
        ].reduce(se3.product);
    };

    context.keys.forEach(key => {
        switch (key) {
            case 'KeyW':
                move(0.5, 0.0);
                return;
            case 'KeyA':
                move(0.0, -0.5);
                return;
            case 'KeyS':
                move(-0.5, 0.0);
                return;
            case 'KeyD':
                move(0.0, 0.5);
                return;
            case 'KeyQ':
                roll(0.02);
                return;
            case 'KeyE':
                roll(-0.02);
                return;
            case 'KeyR':
                context.timeOffset += 1;
                return;
        }
    });
}

function slerp(current: linalg.Mat4, target: linalg.Mat4, maxVelocity: number) : linalg.Mat4 {
    const q0 = quat.mat2Quat(current);
    let q1 = quat.mat2Quat(target);

    const dq = quat.diff(q1, q0);
    const maxt = maxVelocity / quat.norm(dq);

    //const q = quat.normalize(quat.add(q0, quat.scale(dq, Math.min(1, maxt))));
    const t = maxVelocity;
    if (quat.dot(q0, q1) < 0) {
        q1 = quat.scale(q1, -1);
    }
    const q = quat.normalize(quat.add(quat.scale(q0, 1 - t), quat.scale(q1, t)));
    return quat.quat2Mat(q);
}

function distanceToGround(body: Body, position: number[], direction: number[]) : number {
    const inChunkOrientation = se3.inverse(body.orientation);
    const toChunk = vec => se3.apply(inChunkOrientation, vec.concat([0]));
    const directionInChunk = toChunk(direction);
    const positionInChunk = toChunk(linalg.diff(position, body.position));

    const hit = castRay(body.geometry.chunkMap, positionInChunk, directionInChunk);

    if (hit === undefined || hit.block.type === BlockType.UNDEFINED || hit.block.type === undefined) {
        const ray = linalg.diff(position, body.position);
        return {
            distance: linalg.norm(ray),
            normal: linalg.normalize(ray),
        };
    }
    
    const distance = linalg.norm(linalg.diff(positionInChunk, hit.block.centerPosition));
    const normal = se3.apply(body.orientation, hit.normal.concat([0]));
    return {distance, normal};
}

function finishLanding(context, body) {
    const p = context.player;
    context.landed = true;
    context.landedBody = body;

    p.tf = [
        se3.inverse(body.orientation),
        se3.inverse(se3.translation(...body.position)),
        p.tf,
    ].reduce(se3.product);
    p.velocity = [0, 0, 0];
    p.position = se3.apply(p.tf, [0, 0, 0, 1]);
}

function alignUp(playerTf, surfaceNormal) {
    const zaxis = se3.apply(playerTf, [0, 0, 1, 0]);
    const ny = surfaceNormal;
    const nx = linalg.normalize(linalg.cross(ny, zaxis));
    const nz = linalg.normalize(linalg.cross(nx, ny));

    return se3.fromBases(nx, ny, nz);
}

function calculateLandingDv(verticalSpeed, altitude, dt) {
    // pretty crude logic, could be improved
    const maxThrust = 2;
    const final = verticalSpeed**2 / (2*(altitude - 1.0));

    if (verticalSpeed > 0 || final < maxThrust * 0.8) {
        // can still accelerate forward
        return -maxThrust * dt;
    } else if (final < maxThrust) {
        // coast
        return 0;
    }
    return final;
}

function autoLand(context, dt) {
    const p = context.player;
    // 0. check prereqs:
    //   - none
    // 1. adjust tangential speed to match body rotational
    // 2. cast ray towards center
    // 3. while high, go towards center
    // 4. when low, go towards ground
    // 5. stop when on ground
    const kShipRotateSpeed = 0.1;

    const body = findSoi(context.universe, p.position);
    const toBodyCenter = linalg.diff(body.position, p.position);
    const {distance: altitude, normal: surfaceNormal} = distanceToGround(body, p.position, linalg.normalize(toBodyCenter));

    const surfaceVelocity = linalg.add(body.velocity, linalg.cross(body.spin, linalg.scale(toBodyCenter, -1)));
    const relativeVelocity = linalg.diff(p.velocity, surfaceVelocity);
    const upward = linalg.dot(relativeVelocity, surfaceNormal);
    const vertical = linalg.scale(surfaceNormal, upward);
    const horizontal = linalg.diff(relativeVelocity, vertical);
    const smallDv = linalg.scale(horizontal, -0.01);
    p.velocity = linalg.add(p.velocity, smallDv);

    // up is up
    const currentOrientation = slerp(p.tf, alignUp(p.tf, surfaceNormal), kShipRotateSpeed);
    p.tf = se3.setOrientation(p.tf, currentOrientation);

    if (altitude < 1.5) {
        if (upward < -2) {
            // going too fast, bounce
            p.velocity = linalg.add(p.velocity, linalg.scale(surfaceNormal, -2*upward));
            context.landing = false;
        } else if (upward < 0) {
            finishLanding(context, body);
            return;
        }
    }

    // accelerate towards the ground and then slow down to land
    const dvup = calculateLandingDv(upward, altitude, dt);
    p.velocity = linalg.add(p.velocity, linalg.scale(surfaceNormal, dvup));
}

function effectiveGravity(position: number[], rootBody: Body) : number[] {
    let body = rootBody;
    let acceleration = [0, 0, 0];
    while (body !== undefined) {
        const toBodyCenter = linalg.diff(body.position, position);
        const d = linalg.norm(toBodyCenter);
        const gravity = body.mass / d**3;
        acceleration = linalg.add(acceleration, linalg.scale(toBodyCenter, gravity));

        const parentMass = body.mass;
        const children = body.children || [];
        body = undefined;
        for (const child of children) {
            if (!isInSoi(child, parentMass, position)) {
                continue;
            }
            body = child;
            break;
        }
    }

    return acceleration;
}

function updatePhysics(time: number, context) {
    const {player} = context;
    const dt = time - (context.lastTime || 0);
    context.lastTime = time;

    player.position = se3.apply(player.tf, [0, 0, 0, 1]);

    if (!context.pause) {
        updateBodyPhysics(time, context.universe);
    }

    const kShipRotateSpeed = 0.1;

    if (context.landed) {
        return; // TODO: implement
    }

    if (context.landing) {
        autoLand(context, dt);
    } else {
        // allow adjusting camera
        const dr = slerp(se3.identity(), context.camera.tf, kShipRotateSpeed);
        player.tf = se3.product(player.tf, dr);
        context.camera.tf = se3.product(context.camera.tf, se3.inverse(dr));
    }

    if (context.flying) {
        // no physics, just magically moving around
        return;
    }

    const gravity = effectiveGravity(player.position, context.universe);
    player.velocity = linalg.add(player.velocity, linalg.scale(gravity, dt));

    const newPos = linalg.add(player.position, linalg.scale(player.velocity, dt));
    player.tf = se3.setPosition(player.tf, newPos);

    if (context.orbit === undefined) {
        const body = findSoi(context.universe, context.player.position);
        context.orbit = computeOrbit(player, body, time);
        console.log(`orbiting ${body.name}, excentricity: ${context.orbit.excentricity}`);
        context.orbitBody = body;
    }
}

function updateGeometry(context, timeout_ms = 10) {
}

function tick(time: number, context) {
    handleInput(context);
    const simTime = time * 0.001 + context.timeOffset;
    updatePhysics(simTime, context);

    // world generation / geometry update
    {
        // frame time is typically 16.7ms, so this may lag a bit
        let timeLeft = 10;
        const start = performance.now();
        updateGeometry(context, timeLeft);
    }

    draw(context);

    const dt = (time - context.lastFrameTime) * 0.001;
    context.lastFrameTime = time;

    document.querySelector('#fps')!.textContent = `${1.0 / dt} fps`;

    requestAnimationFrame(time => tick(time, context));
}

function makeCube(texture) {
    return {
        faces: [
            makeFace('-x', texture, [-0.5, 0, 0]),
            makeFace('+x', texture, [+0.5, 0, 0]),
            makeFace('-y', texture, [0, -0.5, 0]),
            makeFace('+y', texture, [0, +0.5, 0]),
            makeFace('-z', texture, [0, 0, -0.5]),
            makeFace('+z', texture, [0, 0, +0.5]),
        ]
    };
}

async function main() {
    const canvas = document.querySelector('#game')! as HTMLCanvasElement;
    // adjust canvas aspect ratio to that of the screen
    canvas.height = screen.height / screen.width * canvas.width;
    const gl = canvas.getContext('webgl');

    if (gl === null) {
        console.error('webgl not available')
        return;
    }

    // TODO
    // [ ] loading bar
    // [x] spaceship
    // [ ] landing
    // [ ] huge planets
    // [x] lighting
    // [x] better lighting
    // [ ] betterer lighting
    // [x] optimize geometry generation

    const modelPromise = loadObjModel('spaceship.obj');

    const context = {
        gl,
        projMatrix: se3.perspective(Math.PI / 3, canvas.clientWidth / canvas.clientHeight, 0.1, 10000.0),
        player: {
            tf: se3.translation(0.0, 0.0, 80.0),
            position: [0.0, 0.0, 80.0],
            velocity: [0, 0, 0],
        },
        camera: {
            orientation: [0, 0, 0],
            tf: se3.identity(),
        },
        keys: new Set(),
        lightDirection: [-0.2, -0.5, 0.4],
        skyColor: [0.10, 0.15, 0.2],
        ambiantLight: 0.4,
        blockSelectDistance: 8,
        flying: true,
        isOnGround: false,
        gravity: -17,
        jumpForce: 6.5,
        universe: getSolarSystem(0),
        timeOffset: 0,
    };

    context.glContext = await initWorldGl(gl);
    context.orbitGlContext = getOrbitDrawContext(gl);
    initUiListeners(canvas, context);

    const starshipGeom = await modelPromise;

    context.spaceship = starshipGeom;

    requestAnimationFrame(time => tick(time, context));
}

window.onload = main;