let selected = null;
let selectedEntity = null;

let entityIndex = 0;

let clicked = null;
let dragging = false;
let clickTimeout = null;
let dragOffsetX = null;
let dragOffsetY = null;

let altHeld = false;

const unitChoices = {
    length: [
        "meters",
        "kilometers"
    ],
    mass: [
        "kilograms"
    ]
}
const config = {
    height: math.unit(10, "meters"),
    minLineSize: 50,
    maxLineSize: 250
}

const entities = {

}

function constrainRel(coords) {
    return {
        x: Math.min(Math.max(coords.x, 0), 1),
        y: Math.min(Math.max(coords.y, 0), 1)
    }
}
function snapRel(coords) {
    return constrainRel({
        x: coords.x,
        y: altHeld ? coords.y : (Math.abs(coords.y - 1) < 0.05 ? 1 : coords.y)
    });
}

function adjustAbs(coords, oldHeight, newHeight) {
    return { x: coords.x, y: 1 + (coords.y - 1) * math.divide(oldHeight, newHeight) };
}

function rel2abs(coords) {
    const canvasWidth = document.querySelector("#display").clientWidth - 50;
    const canvasHeight = document.querySelector("#display").clientHeight - 50;

    return { x: coords.x * canvasWidth, y: coords.y * canvasHeight };
}

function abs2rel(coords) {
    const canvasWidth = document.querySelector("#display").clientWidth - 50;
    const canvasHeight = document.querySelector("#display").clientHeight - 50;

    return { x: coords.x / canvasWidth, y: coords.y / canvasHeight };
}

function updateEntityElement(entity, element) {
    const position = rel2abs({ x: element.dataset.x, y: element.dataset.y });
    const view = element.dataset.view;

    element.style.left = position.x + "px";
    element.style.top = position.y + "px";
    const canvasHeight = document.querySelector("#display").clientHeight;
    const pixels = math.divide(entity.views[view].height, config.height) * (canvasHeight - 100);
    element.style.setProperty("--height", pixels + "px");

    element.querySelector(".entity-name").innerText = entity.name;

    const bottomName = document.querySelector("#bottom-name-" + element.dataset.key);

    let entX = document.querySelector("#entities").getBoundingClientRect().x;
    bottomName.style.left = position.x + entX + "px";
    bottomName.style.top = "95vh";
    bottomName.innerText = entity.name;
}

function updateSizes() {
    drawScale();
    Object.entries(entities).forEach(([key, entity]) => {
        const element = document.querySelector("#entity-" + key);
        updateEntityElement(entity, element);
    });
}

function drawScale() {
    function drawTicks(/** @type {CanvasRenderingContext2D} */ ctx, pixelsPer, heightPer) {
        let total = heightPer.clone();
        total.value = 0;
        for (let y = ctx.canvas.clientHeight - 50; y >= 50; y -= pixelsPer) {
            drawTick(ctx, 50, y, total);
            total = math.add(total, heightPer);
        }
    }

    function drawTick(/** @type {CanvasRenderingContext2D} */ ctx, x, y, value) {
        const oldStroke = ctx.strokeStyle;
        const oldFill = ctx.fillStyle;

        ctx.beginPath();
        ctx.moveTo(x, y);
        ctx.lineTo(x + 20, y);
        ctx.strokeStyle = "#000000";
        ctx.stroke();

        ctx.beginPath();
        ctx.moveTo(x + 20, y);
        ctx.lineTo(ctx.canvas.clientWidth - 70, y);
        ctx.strokeStyle = "#aaaaaa";
        ctx.stroke();

        ctx.beginPath();
        ctx.moveTo(ctx.canvas.clientWidth - 70, y);
        ctx.lineTo(ctx.canvas.clientWidth - 50, y);
        ctx.strokeStyle = "#000000";
        ctx.stroke();

        const oldFont = ctx.font;
        ctx.font = 'normal 24pt coda';
        ctx.fillStyle = "#dddddd";

        ctx.beginPath();
        ctx.fillText(value.format({ precision: 3 }), x + 20, y + 35);

        ctx.font = oldFont;
        ctx.strokeStyle = oldStroke;
        ctx.fillStyle = oldFill;
    }
    const canvas = document.querySelector("#display");

    /** @type {CanvasRenderingContext2D} */

    const ctx = canvas.getContext("2d");

    let pixelsPer = (ctx.canvas.clientHeight - 100) / config.height.value;
    let heightPer = config.height.clone();
    heightPer.value = 1;

    if (pixelsPer < config.minLineSize) {
        heightPer.value /= pixelsPer / config.minLineSize;
        pixelsPer = config.minLineSize;
    }

    if (pixelsPer > config.maxLineSize) {
        heightPer.value /= pixelsPer / config.maxLineSize;
        pixelsPer = config.maxLineSize;
    }

    ctx.clearRect(0, 0, canvas.width, canvas.height);
    ctx.scale(1, 1);
    ctx.canvas.width = canvas.clientWidth;
    ctx.canvas.height = canvas.clientHeight;

    ctx.beginPath();
    ctx.moveTo(50, 50);
    ctx.lineTo(50, ctx.canvas.clientHeight - 50);
    ctx.stroke();
    ctx.beginPath();
    ctx.moveTo(ctx.canvas.clientWidth - 50, 50);
    ctx.lineTo(ctx.canvas.clientWidth - 50, ctx.canvas.clientHeight - 50);
    ctx.stroke();

    drawTicks(ctx, pixelsPer, heightPer);
}

function makeEntity() {
    const entityTemplate = {
        name: "",
        author: "",
        scale: 1,
        views: {
            body: {
                attributes: {
                    height: {
                        name: "Height",
                        power: 1,
                        type: "length",
                        base: math.unit(1, "meter")
                    },
                    weight: {
                        name: "Weight",
                        power: 3,
                        type: "mass",
                        base: math.unit(80, "kg")
                    }
                },
                image: "./silhouette.png",
                name: "Body"
            },
            pepper: {
                attributes: {
                    height: {
                        name: "Height",
                        power: 1,
                        type: "length",
                        base: math.unit(50, "centimeter")
                    },
                    weight: {
                        name: "Weight",
                        power: 3,
                        type: "mass",
                        base: math.unit(1, "kg")
                    }
                },
                image: "./pepper.png",
                name: "Pepper"
            }
        },
        init: function () {
            Object.values(this.views).forEach(view => {
                view.parent = this;

                Object.entries(view.attributes).forEach(([key, val]) => {
                    Object.defineProperty(
                        view,
                        key,
                        {
                            get: function() {
                                return math.multiply(Math.pow(this.parent.scale, this.attributes[key].power), this.attributes[key].base);
                            },
                            set: function(value) {
                                const newScale = Math.pow(math.divide(value, this.attributes[key].base), 1 / this.attributes[key].power);
                                this.parent.scale = newScale;
                            }
                        }
                    )
                });
            });
            delete this.init;
            return this;
        }
    }.init();

    return entityTemplate;
}

function clickDown(target, x, y) {
    clicked = target;
    const rect = target.getBoundingClientRect();
    let entX = document.querySelector("#entities").getBoundingClientRect().x;
    let entY = document.querySelector("#entities").getBoundingClientRect().y;
    dragOffsetX = x - rect.left + entX;
    dragOffsetY = y - rect.top + entY;
    clickTimeout = setTimeout(() => { dragging = true }, 200)
}

function clickUp() {
    clearTimeout(clickTimeout);

    if (clicked) {
        if (dragging) {
            dragging = false;
        } else {
            select(clicked);
        }
        clicked = null;
    }

}

function deselect() {
    if (selected) {
        selected.classList.remove("selected");
    }
    selected = null;
    clearViewList();
    clearEntityOptions();
    clearViewOptions();
}

function select(target) {
    deselect();
    selected = target;
    selectedEntity = entities[target.dataset.key];

    selected.classList.add("selected");

    entityInfo(selectedEntity, target.dataset.view);
    configViewList(selectedEntity, target.dataset.view);
    configEntityOptions(selectedEntity, target.dataset.view);
    configViewOptions(selectedEntity, target.dataset.view);
}

function entityInfo(entity, view) {
    document.querySelector("#entity-name").innerText = "Name: " + entity.name;
    document.querySelector("#entity-author").innerText = "Author: " + entity.author;
    document.querySelector("#entity-height").innerText = "Height: " + entity.views[view].height.format({ precision: 3 });
}

function configViewList(entity, selectedView) {
    const list = document.querySelector("#entity-view");
    
    list.innerHTML = "";

    list.style.display = "block";

    Object.keys(entity.views).forEach(view => {
        const option = document.createElement("option");
        option.innerText = entity.views[view].name;
        option.value = view;

        if (view === selectedView) {
            option.selected = true;
        }
        list.appendChild(option);
    });
}

function clearViewList() {
    const list = document.querySelector("#entity-view");
    
    list.innerHTML = "";
    list.style.display = "none";
}

function configEntityOptions(entity, view) {
    const holder = document.querySelector("#options-entity");

    holder.innerHTML = "";

    const scaleLabel = document.createElement("div");
    scaleLabel.classList.add("options-label");
    scaleLabel.innerText = "Scale";

    const scaleRow = document.createElement("div");
    scaleRow.classList.add("options-row");

    const scaleInput = document.createElement("input");
    scaleInput.classList.add("options-field-numeric");
    scaleInput.id = "options-entity-scale";

    scaleInput.addEventListener("input", e => {
        entity.scale = e.target.value;
        updateSizes();
        updateEntityOptions(entity, view);
        updateViewOptions(entity, view);
    });

    scaleInput.setAttribute("min", 1);
    scaleInput.setAttribute("type", "number");
    scaleInput.value = entity.scale;

    scaleRow.appendChild(scaleInput);
    holder.appendChild(scaleLabel);
    holder.appendChild(scaleRow);

    const nameLabel = document.createElement("div");
    nameLabel.classList.add("options-label");
    nameLabel.innerText = "Name";

    const nameRow = document.createElement("div");
    nameRow.classList.add("options-row");
    
    const nameInput = document.createElement("input");
    nameInput.classList.add("options-field-text");
    nameInput.value = entity.name;

    nameInput.addEventListener("input", e => {
        entity.name = e.target.value;
        updateSizes();
    })

    nameRow.appendChild(nameInput);

    holder.appendChild(nameLabel);
    holder.appendChild(nameRow);
}

function updateEntityOptions(entity, view) {
    const scaleInput = document.querySelector("#options-entity-scale");
    scaleInput.value = entity.scale;
}

function clearEntityOptions() {
    const holder = document.querySelector("#options-entity");

    holder.innerHTML = "";
}

function configViewOptions(entity, view) {
    const holder = document.querySelector("#options-view");

    holder.innerHTML = "";

    Object.entries(entity.views[view].attributes).forEach(([key, val]) => {
        const label = document.createElement("div");
        label.classList.add("options-label");
        label.innerText = val.name;

        holder.appendChild(label);

        const row = document.createElement("div");
        row.classList.add("options-row");

        holder.appendChild(row);

        const input = document.createElement("input");
        input.classList.add("options-field-numeric");
        input.id = "options-view-" + key + "-input";
        input.setAttribute("type", "number");
        input.setAttribute("min", 1);

        input.value = entity.views[view][key].value;

        const select = document.createElement("select");
        select.id = "options-view-" + key + "-select"

        unitChoices[val.type].forEach(name => {
            const option = document.createElement("option");
            option.innerText = name;
            select.appendChild(option);
        });
        

        input.addEventListener("input", e => {
            entity.views[view][key] = math.unit(input.value, select.value);
            updateSizes();
            updateEntityOptions(entity, view);
            updateViewOptions(entity, view, key);
        });

        select.addEventListener("input", e => {
            entity.views[view][key] = math.unit(input.value, select.value);
            updateSizes();
            updateEntityOptions(entity, view);
            updateViewOptions(entity, view, key);
        });

        row.appendChild(input);
        row.appendChild(select);
    });
    
}

function updateViewOptions(entity, view, changed) {
    Object.entries(entity.views[view].attributes).forEach(([key, val]) => {
        if (key != changed) {
            const input = document.querySelector("#options-view-" + key + "-input");
            const select = document.querySelector("#options-view-" + key + "-select");
            const currentUnit = select.value;
            const convertedAmount = entity.views[view][key].to(currentUnit);
            console.log(convertedAmount);
            input.value = math.round(convertedAmount.value, 5);
        }
        
    });
}

function clearViewOptions() {
    const holder = document.querySelector("#options-view");

    holder.innerHTML = "";
}

// this is a crime against humanity, and also stolen from
// stack overflow
// https://stackoverflow.com/questions/38487569/click-through-png-image-only-if-clicked-coordinate-is-transparent

const testCanvas = document.createElement("canvas");
testCanvas.id = "test-canvas";

const testCtx = testCanvas.getContext("2d");
function testClick(event) {
    const target = event.target;
    // Get click coordinates
    var x = event.clientX - target.getBoundingClientRect().x,
        y = event.clientY - target.getBoundingClientRect().y,
        w = testCtx.canvas.width = target.width,
        h = testCtx.canvas.height = target.height,
        alpha;

    // Draw image to canvas
    // and read Alpha channel value
    testCtx.drawImage(target, 0, 0, w, h);
    alpha = testCtx.getImageData(x, y, 1, 1).data[3]; // [0]R [1]G [2]B [3]A

    // If pixel is transparent,
    // retrieve the element underneath and trigger it's click event
    if (alpha === 0) {
        const oldDisplay = target.style.display;
        target.style.display = "none";
        const newTarget = document.elementFromPoint(event.clientX, event.clientY);
        newTarget.dispatchEvent(new MouseEvent(event.type, {
            "clientX": event.clientX,
            "clientY": event.clientY
        }));
        target.style.display = oldDisplay;
    } else {
        clickDown(target.parentElement, event.clientX, event.clientY);
    }
}

function displayEntity(entity, view, x, y) {
    const box = document.createElement("div");
    box.classList.add("entity-box");

    const img = document.createElement("img");
    img.classList.add("entity-image");
    const nameTag = document.createElement("div");
    nameTag.classList.add("entity-name");
    nameTag.innerText = entity.name;
    box.appendChild(img);
    box.appendChild(nameTag);

    img.src = entity.views[view].image

    box.dataset.x = x;
    box.dataset.y = y;

    img.addEventListener("mousedown", e => { testClick(e); e.stopPropagation() });
    img.addEventListener("touchstart", e => { 
        const fakeEvent = {
            target: e.target,
            clientX: e.touches[0].clientX,
            clientY: e.touches[0].clientY
        };
        testClick(fakeEvent);});

    box.id = "entity-" + entityIndex;
    box.dataset.key = entityIndex;
    box.dataset.view = view;

    entities[entityIndex] = entity;

    const world = document.querySelector("#entities");
    world.appendChild(box);

    const bottomName = document.createElement("div");
    bottomName.classList.add("bottom-name");
    bottomName.id = "bottom-name-" + entityIndex;
    bottomName.innerText = entity.name;

    bottomName.addEventListener("click", () => select(box));

    world.appendChild(bottomName);
    entityIndex += 1;

    updateEntityElement(entity, box);
}

document.addEventListener("DOMContentLoaded", () => {
    for (let x = 0; x < 5; x++) {
        const entity = makeEntity();
        entity.name = "Dude";
        entity.author = "Fen"
        const x = 0.25 + Math.random() * 0.5;
        const y = 0.25 + Math.random() * 0.5;
        displayEntity(entity, "body", x, y);
    }
    document.querySelector("body").appendChild(testCtx.canvas);

    updateSizes();

    document.querySelector("#options-height-value").addEventListener("input", e => {
        updateWorldHeight();
    })

    document.querySelector("#options-height-unit").addEventListener("input", e => {
        updateWorldHeight();
    })

    world.addEventListener("mousedown", e => deselect());
    document.addEventListener("mouseup", e => clickUp());
    document.addEventListener("touchend", e => clickUp());

    document.querySelector("#entity-view").addEventListener("input", e => {
        selected.dataset.view = e.target.value
        selected.querySelector(".entity-image").src = entities[selected.dataset.key].views[e.target.value].image;
        updateSizes();
        updateEntityOptions(entities[selected.dataset.key], e.target.value);
        updateViewOptions(entities[selected.dataset.key], e.target.value);
    });

    clearViewList();
});

window.addEventListener("resize", () => {
    updateSizes();
})

document.addEventListener("mousemove", (e) => {
    if (clicked) {
        const position = snapRel(abs2rel({ x: e.clientX - dragOffsetX, y: e.clientY - dragOffsetY }));
        clicked.dataset.x = position.x;
        clicked.dataset.y = position.y;
        updateEntityElement(entities[clicked.dataset.key], clicked);
    }
});

document.addEventListener("touchmove", (e) => {
    if (clicked) {
        e.preventDefault();
        let x = e.touches[0].clientX;
        let y = e.touches[0].clientY;

        const position = snapRel(abs2rel({ x: x - dragOffsetX, y: y - dragOffsetY }));
        clicked.dataset.x = position.x;
        clicked.dataset.y = position.y;
        updateEntityElement(entities[clicked.dataset.key], clicked);
    }
}, {passive: false});

function updateWorldHeight() {
    const value = Math.max(1, document.querySelector("#options-height-value").value);
    const unit = document.querySelector("#options-height-unit").value;
    const oldHeight = config.height;

    config.height = math.unit(value + " " + unit)

    Object.entries(entities).forEach(([key, entity]) => {
        const element = document.querySelector("#entity-" + key);
        const newPosition = adjustAbs({ x: element.dataset.x, y: element.dataset.y }, oldHeight, config.height);
        element.dataset.x = newPosition.x;
        element.dataset.y = newPosition.y;
    });

    updateSizes();
}