import { makeBufferFromFaces } from "./geometry";
import * as se3 from './se3';
import { checkCollision, destroySelectedBlock, generateMissingChunks, markBlock, updateWorldGeometry } from './world';

/** Draw.
 *
 * @param {WebGLRenderingContext} gl
 */
function draw(gl, params, objects) {
    const skyColor = [0.6, 0.8, 1.0];

    gl.clearColor(...skyColor, 1.0);
    gl.clearDepth(1.0);
    gl.enable(gl.DEPTH_TEST);
    gl.depthFunc(gl.LEQUAL);

    gl.enable(gl.CULL_FACE);
    gl.cullFace(gl.BACK);
    gl.enable(gl.BLEND);
    gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    const camrot = params.camera.orientation;
    const campos = params.camera.position;
    const viewMatrix = se3.product(
        se3.rotxyz(-camrot[0], -camrot[1], -camrot[2]),
        se3.translation(-campos[0], -campos[1], -campos[2])
    );

    let lastGlContext;

    for (const {glContext, position, orientation, geometry} of objects) {
        if (glContext !== lastGlContext) {
            glContext.setupScene({
                projectionMatrix: params.projMatrix,
                viewMatrix,
                fogColor: skyColor,
                lightDirection: params.lightDirection,
                ambiantLightAmount: params.ambiantLight,
            });
        }

        lastGlContext = glContext;

        glContext.drawObject({
            position,
            orientation,
            glBuffer: geometry.glBuffer,
            numVertices: geometry.numVertices,
        });
    }
}

const stuff = {
    lastFrameTime: 0,
};

function handleKeys(params) {
    const move = (forward, right) => {
        const dir = [right, 0, -forward, 1.0];
        const ori = se3.roty(params.camera.orientation[1]);
        const tf = se3.apply(ori, dir);

        if (params.flying) {
            params.camera.position[0] += tf[0];
            params.camera.position[2] += tf[2];
        }
        if (params.isOnGround) {
            params.camera.velocity[0] = tf[0];
            params.camera.velocity[2] = tf[2];
        } else {
            params.camera.velocity[0] += tf[0] / 60;
            params.camera.velocity[2] += tf[2] / 60;

            if (Math.abs(params.camera.velocity[0]) > Math.abs(tf[0])) {
                params.camera.velocity[0] = tf[0];
            }
            if (Math.abs(params.camera.velocity[2]) > Math.abs(tf[2])) {
                params.camera.velocity[2] = tf[2];
            }
        }
    };

    params.keys.forEach(key => {
        switch (key) {
            case 'KeyW':
                move(0.1, 0.0);
                return;
            case 'KeyA':
                move(0.0, -0.1);
                return;
            case 'KeyS':
                move(-0.1, 0.0);
                return;
            case 'KeyD':
                move(0.0, 0.1);
                return;

            case 'Space':
                if(params.flying) {
                    params.camera.position[1] += 0.1;
                } else {
                    if (params.jumpAmount > 0) {
                        const amount = 0.4 * params.jumpAmount;
                        params.camera.velocity[1] += amount / 60;
                        params.jumpAmount -= amount;
                    }
                }
                return;
            case 'ControlLeft':
                params.camera.position[1] -= 0.1;
                return;
        }
    });
}

function getObjects(world, z, x, glContext) {
    return world.chunks
        .filter(chunk => {
            if (chunk.position.z < z - 8 * 16) return false;
            if (chunk.position.z > z + 7 * 16) return false;
            if (chunk.position.x < x - 8 * 16) return false;
            if (chunk.position.x > x + 7 * 16) return false;

            if (chunk.buffer === undefined) {
                return false;
            }

            return true;
        })
        .map(chunk => ({
            position: [0.0, 0.0, 0.0],
            orientation: [0.0, 0.0, 0.0],
            geometry: chunk.buffer,
            glContext,
        }));
}

function updatePhysics(params) {
    params.camera.velocity[1] -= 9.8 / 60 / 60;

    const oldPos = params.camera.position;
    const targetPos = params.flying ? oldPos : params.camera.position.map((v, i) => v + params.camera.velocity[i]);
    const {isOnGround, newPos} = checkCollision(oldPos, targetPos, params.world);
    params.camera.position = newPos;
    params.camera.velocity = newPos.map((v, i) => v - oldPos[i]);
    if (isOnGround) {
        params.jumpAmount = 6;
        params.camera.velocity = params.camera.velocity.map(v => v * 0.7);
    }
    params.isOnGround = isOnGround;
}

function tagABlock(gl, params, objects) {
    const dir = [0, 0, -1, 1.0];
    const camori = params.camera.orientation;
    const ori = se3.inverse(se3.rotxyz(-camori[0], -camori[1], -camori[2]));
    const viewDirection = se3.apply(ori, dir).slice(0, 3);

    const face = markBlock(params.world, params.camera.position, viewDirection, params.blockSelectDistance);
    if (face === undefined) {
        return;
    }

    if (params.tagBuffer !== undefined) {
        gl.deleteBuffer(params.tagBuffer.glBuffer);
        delete params.tagBuffer;
    }
    const buffer = makeBufferFromFaces(gl, [face]);
    params.tagBuffer = buffer;

    const obj =  {
            position: [0.0, 0.0, 0.0],
            orientation: [0.0, 0.0, 0.0],
            geometry: buffer,
            glContext: params.worldGl,
    };

    objects.push(obj);
}

// Mine & place
// ------------
// [x] ray casting
// [x] block outline
// [ ] crosshair
// [ ] dynamic terrain re-rendering
// [ ] should use a linked list of air contact blocks
//    --> might not be needed. Only need to re-render a single chunk,
//        should be fast enough. We render 16 of them every time we
//        walk 16 blocks in any direction.

// Stuff I need to do:
// [x] a skybox
// [x] a movable camera
// [x] some kind of gravity
// [x] collision detection
// [x] more blocks
// [ ] ability to mine & place
// [x] generating & loading of more chunks
// [x] distance fog
// [ ] different biomes (with different noise stats)
// [ ] non-flowy water
// [ ] flowy water
// [ ] ALIGN CHUNK WITH WORLD COORDS
// [x] better controls
// [ ] save the world (yay) to local storage (bah)

export function setupParamPanel(params) {
    document.querySelector('#lightx').oninput = e => {
        params.lightDirection[0] = e.target.value / 100;
    };
    document.querySelector('#lighty').oninput = e => {
        params.lightDirection[1] = e.target.value / 100;
    };
    document.querySelector('#lightz').oninput = e => {
        params.lightDirection[2] = e.target.value / 100;
    };
    document.querySelector('#ambiant').oninput = e => {
        params.ambiantLight = e.target.value / 100;
    };

    const collapsibles = document.getElementsByClassName("collapsible");
    for (const collapsible of collapsibles) {
        collapsible.onclick = () => {
            const content = collapsible.nextElementSibling;
            if (content.style.height === 'fit-content') {
                content.style.height = '0px';
            } else {
                content.style.height = 'fit-content';
            }
        };
    }
}

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

                switch (e.code) {
                    case 'KeyF':
                        params.flying = !params.flying;
                }
            } else {
                params.keys.delete(e.code);
            }
        };
        const moveListener = e => {
            params.camera.orientation[1] -= e.movementX / 500;
            params.camera.orientation[0] -= e.movementY / 500;

            params.camera.orientation[0] = Math.min(Math.max(
                params.camera.orientation[0], -Math.PI / 2
            ), Math.PI / 2);
        };
        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;
}

export function tick(time, gl, params) {
    handleKeys(params);
    updatePhysics(params);

    const campos = params.camera.position;

    // expensive stuff, can take several cycles
    try {
        // frame time is typically 16.7ms, so this may lag a bit
        let timeLeft = 30;
        const start = performance.now();
        generateMissingChunks(params.world, campos[2], campos[0], timeLeft);

        timeLeft -= performance.now() - start;
        updateWorldGeometry(gl, params.world, campos[2], campos[0], timeLeft);
    }
    catch (ex) {
        if (ex !== 'timesup') {
            throw ex;
        }
    }

    const objects = getObjects(params.world, campos[2], campos[0], params.worldGl);

    tagABlock(gl, params, objects);

    draw(gl, params, objects);

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

    document.querySelector('#fps').textContent = `${1.0 / dt} fps`;
    document.querySelector('#lightDirVec').textContent = JSON.stringify(params.lightDirection);

    requestAnimationFrame(time => tick(time, gl, params));
}