import { globalConfig } from "../../core/config";
import { DrawParameters } from "../../core/draw_parameters";
import { createLogger } from "../../core/logging";
import { Rectangle } from "../../core/rectangle";
import { StaleAreaDetector } from "../../core/stale_area_detector";
import { enumDirection, enumDirectionToVector } from "../../core/vector";
import { BaseItem } from "../base_item";
import { BeltComponent } from "../components/belt";
import { ItemAcceptorComponent } from "../components/item_acceptor";
import { ItemEjectorComponent } from "../components/item_ejector";
import { Entity } from "../entity";
import { GameSystemWithFilter } from "../game_system_with_filter";
import { MapChunkView } from "../map_chunk_view";

const logger = createLogger("systems/ejector");

export class ItemEjectorSystem extends GameSystemWithFilter {
    constructor(root) {
        super(root, [ItemEjectorComponent]);

        this.staleAreaDetector = new StaleAreaDetector({
            root: this.root,
            name: "item-ejector",
            recomputeMethod: this.recomputeArea.bind(this),
        });

        this.staleAreaDetector.recomputeOnComponentsChanged(
            [ItemEjectorComponent, ItemAcceptorComponent, BeltComponent],
            1
        );

        this.root.signals.postLoadHook.add(this.recomputeCacheFull, this);
    }

    /**
     * Recomputes an area after it changed
     * @param {Rectangle} area
     */
    recomputeArea(area) {
        /** @type {Set<number>} */
        const seenUids = new Set();
        for (let x = 0; x < area.w; ++x) {
            for (let y = 0; y < area.h; ++y) {
                const tileX = area.x + x;
                const tileY = area.y + y;
                // @NOTICE: Item ejector currently only supports regular layer
                const contents = this.root.map.getLayerContentXY(tileX, tileY, "regular");
                if (contents && contents.components.ItemEjector) {
                    if (!seenUids.has(contents.uid)) {
                        seenUids.add(contents.uid);
                        this.recomputeSingleEntityCache(contents);
                    }
                }
            }
        }
    }

    /**
     * Recomputes the whole cache after the game has loaded
     */
    recomputeCacheFull() {
        logger.log("Full cache recompute in post load hook");
        for (let i = 0; i < this.allEntities.length; ++i) {
            const entity = this.allEntities[i];
            this.recomputeSingleEntityCache(entity);
        }
    }

    /**
     * @param {Entity} entity
     */
    recomputeSingleEntityCache(entity) {
        const ejectorComp = entity.components.ItemEjector;
        const staticComp = entity.components.StaticMapEntity;

        for (let slotIndex = 0; slotIndex < ejectorComp.slots.length; ++slotIndex) {
            const ejectorSlot = ejectorComp.slots[slotIndex];

            // Clear the old cache.
            ejectorSlot.cachedDestSlot = null;
            ejectorSlot.cachedTargetEntity = null;
            ejectorSlot.cachedBeltPath = null;

            // Figure out where and into which direction we eject items
            const ejectSlotWsTile = staticComp.localTileToWorld(ejectorSlot.pos);
            const ejectSlotWsDirection = staticComp.localDirectionToWorld(ejectorSlot.direction);
            const ejectSlotWsDirectionVector = enumDirectionToVector[ejectSlotWsDirection];
            const ejectSlotTargetWsTile = ejectSlotWsTile.add(ejectSlotWsDirectionVector);

            // Try to find the given acceptor component to take the item
            // Since there can be cross layer dependencies, check on all layers
            const targetEntities = this.root.map.getLayersContentsMultipleXY(
                ejectSlotTargetWsTile.x,
                ejectSlotTargetWsTile.y
            );

            for (let i = 0; i < targetEntities.length; ++i) {
                const targetEntity = targetEntities[i];

                const targetStaticComp = targetEntity.components.StaticMapEntity;
                const targetBeltComp = targetEntity.components.Belt;

                // Check for belts (special case)
                if (targetBeltComp) {
                    const beltAcceptingDirection = targetStaticComp.localDirectionToWorld(enumDirection.top);
                    if (ejectSlotWsDirection === beltAcceptingDirection) {
                        ejectorSlot.cachedTargetEntity = targetEntity;
                        ejectorSlot.cachedBeltPath = targetBeltComp.assignedPath;
                        break;
                    }
                }

                // Check for item acceptors
                const targetAcceptorComp = targetEntity.components.ItemAcceptor;
                if (!targetAcceptorComp) {
                    // Entity doesn't accept items
                    continue;
                }

                const matchingSlot = targetAcceptorComp.findMatchingSlot(
                    targetStaticComp.worldToLocalTile(ejectSlotTargetWsTile),
                    targetStaticComp.worldDirectionToLocal(ejectSlotWsDirection)
                );

                if (!matchingSlot) {
                    // No matching slot found
                    continue;
                }

                // A slot can always be connected to one other slot only
                ejectorSlot.cachedTargetEntity = targetEntity;
                ejectorSlot.cachedDestSlot = matchingSlot;
                break;
            }
        }
    }

    update() {
        this.staleAreaDetector.update();

        // Precompute effective belt speed
        let progressGrowth = 2 * this.root.dynamicTickrate.deltaSeconds;

        if (G_IS_DEV && globalConfig.debug.instantBelts) {
            progressGrowth = 1;
        }

        // Go over all cache entries
        for (let i = 0; i < this.allEntities.length; ++i) {
            const sourceEntity = this.allEntities[i];
            const sourceEjectorComp = sourceEntity.components.ItemEjector;

            const slots = sourceEjectorComp.slots;
            for (let j = 0; j < slots.length; ++j) {
                const sourceSlot = slots[j];
                const item = sourceSlot.item;
                if (!item) {
                    // No item available to be ejected
                    continue;
                }

                // Advance items on the slot
                sourceSlot.progress = Math.min(
                    1,
                    sourceSlot.progress +
                        progressGrowth *
                            this.root.hubGoals.getBeltBaseSpeed() *
                            globalConfig.itemSpacingOnBelts
                );

                if (G_IS_DEV && globalConfig.debug.disableEjectorProcessing) {
                    sourceSlot.progress = 1.0;
                }

                // Check if we are still in the process of ejecting, can't proceed then
                if (sourceSlot.progress < 1.0) {
                    continue;
                }

                // Check if we are ejecting to a belt path
                const destPath = sourceSlot.cachedBeltPath;
                if (destPath) {
                    // Try passing the item over
                    if (destPath.tryAcceptItem(item)) {
                        sourceSlot.item = null;
                    }

                    // Always stop here, since there can *either* be a belt path *or*
                    // a slot
                    continue;
                }

                // Check if the target acceptor can actually accept this item
                const destEntity = sourceSlot.cachedTargetEntity;
                const destSlot = sourceSlot.cachedDestSlot;
                if (destSlot) {
                    const targetAcceptorComp = destEntity.components.ItemAcceptor;
                    if (!targetAcceptorComp.canAcceptItem(destSlot.index, item)) {
                        continue;
                    }

                    // Try to hand over the item
                    if (this.tryPassOverItem(item, destEntity, destSlot.index)) {
                        // Handover successful, clear slot
                        targetAcceptorComp.onItemAccepted(destSlot.index, destSlot.acceptedDirection, item);
                        sourceSlot.item = null;
                        continue;
                    }
                }
            }
        }
    }

    /**
     *
     * @param {BaseItem} item
     * @param {Entity} receiver
     * @param {number} slotIndex
     */
    tryPassOverItem(item, receiver, slotIndex) {
        // Try figuring out how what to do with the item
        // TODO: Kinda hacky. How to solve this properly? Don't want to go through inheritance hell.
        // Also its just a few cases (hope it stays like this .. :x).

        const beltComp = receiver.components.Belt;
        if (beltComp) {
            const path = beltComp.assignedPath;
            assert(path, "belt has no path");
            if (path.tryAcceptItem(item)) {
                return true;
            }
            // Belt can have nothing else
            return false;
        }

        const itemProcessorComp = receiver.components.ItemProcessor;
        if (itemProcessorComp) {
            // Check for potential filters
            if (!this.root.systemMgr.systems.itemProcessor.checkRequirements(receiver, item, slotIndex)) {
                return false;
            }

            // Its an item processor ..
            if (itemProcessorComp.tryTakeItem(item, slotIndex)) {
                return true;
            }
            // Item processor can have nothing else
            return false;
        }

        const undergroundBeltComp = receiver.components.UndergroundBelt;
        if (undergroundBeltComp) {
            // Its an underground belt. yay.
            if (
                undergroundBeltComp.tryAcceptExternalItem(
                    item,
                    this.root.hubGoals.getUndergroundBeltBaseSpeed()
                )
            ) {
                return true;
            }

            // Underground belt can have nothing else
            return false;
        }

        const storageComp = receiver.components.Storage;
        if (storageComp) {
            // It's a storage
            if (storageComp.canAcceptItem(item)) {
                storageComp.takeItem(item);
                return true;
            }

            // Storage can't have anything else
            return false;
        }

        return false;
    }

    /**
     * @param {DrawParameters} parameters
     * @param {MapChunkView} chunk
     */
    drawChunk(parameters, chunk) {
        const contents = chunk.containedEntitiesByLayer.regular;

        for (let i = 0; i < contents.length; ++i) {
            const entity = contents[i];
            const ejectorComp = entity.components.ItemEjector;
            if (!ejectorComp) {
                continue;
            }

            const staticComp = entity.components.StaticMapEntity;

            for (let i = 0; i < ejectorComp.slots.length; ++i) {
                const slot = ejectorComp.slots[i];
                const ejectedItem = slot.item;

                if (!ejectedItem) {
                    // No item
                    continue;
                }

                if (!ejectorComp.renderFloatingItems && !slot.cachedTargetEntity) {
                    // Not connected to any building
                    continue;
                }

                const realPosition = staticComp.localTileToWorld(slot.pos);
                if (!chunk.tileSpaceRectangle.containsPoint(realPosition.x, realPosition.y)) {
                    // Not within this chunk
                    continue;
                }

                const realDirection = staticComp.localDirectionToWorld(slot.direction);
                const realDirectionVector = enumDirectionToVector[realDirection];

                const tileX = realPosition.x + 0.5 + realDirectionVector.x * 0.5 * slot.progress;
                const tileY = realPosition.y + 0.5 + realDirectionVector.y * 0.5 * slot.progress;

                const worldX = tileX * globalConfig.tileSize;
                const worldY = tileY * globalConfig.tileSize;

                ejectedItem.drawItemCenteredClipped(
                    worldX,
                    worldY,
                    parameters,
                    globalConfig.defaultItemDiameter
                );
            }
        }
    }
}