import maplibregl from "maplibre-gl";
import { Geometry } from "@/lib/useEditorState";

export type EditingHandle = {
    id: string | number;
    ring: [number, number][];
    original: Geometry;
};

export type EditingAPI = {
    beginEditing: (feature: maplibregl.MapGeoJSONFeature) => void;
    clearEditing: () => void;
    bindEditEvents: (map: maplibregl.Map) => void;
};

export function createEditingEngine(options: {
    mapRef: React.MutableRefObject<maplibregl.Map | null>;
    onUpdate: (id: string | number, geometry: Geometry) => void;
}) {
    const { mapRef, onUpdate } = options;
    const editingRef = { current: null as EditingHandle | null };
    const dragStateRef = { current: null as { idx: number } | null };
    const modifierRef = { current: { ctrl: false, meta: false } };

    const clearEditing = () => {
        editingRef.current = null;
        dragStateRef.current = null;
        const map = mapRef.current;
        if (!map) return;
        const empty: GeoJSON.FeatureCollection = { type: "FeatureCollection", features: [] };
        (map.getSource("edit-shape") as maplibregl.GeoJSONSource | undefined)?.setData(empty);
        (map.getSource("edit-handles") as maplibregl.GeoJSONSource | undefined)?.setData(empty);
    };

    const updateEditSources = () => {
        const editing = editingRef.current;
        const map = mapRef.current;
        if (!editing || !map) return;

        const closedRing = [...editing.ring, editing.ring[0]];
        const shape: GeoJSON.FeatureCollection<GeoJSON.Polygon> = {
            type: "FeatureCollection",
            features: [
                {
                    type: "Feature",
                    geometry: { type: "Polygon", coordinates: [closedRing] },
                    properties: {},
                },
            ],
        };

        const handles: GeoJSON.FeatureCollection<GeoJSON.Point> = {
            type: "FeatureCollection",
            features: editing.ring.map((c, idx) => ({
                type: "Feature",
                geometry: { type: "Point", coordinates: c },
                properties: { idx },
            })),
        };

        (map.getSource("edit-shape") as maplibregl.GeoJSONSource | undefined)?.setData(shape);
        (map.getSource("edit-handles") as maplibregl.GeoJSONSource | undefined)?.setData(handles);
    };

    const finishEditing = () => {
        const editing = editingRef.current;
        if (!editing) return;
        const geometry: Geometry = {
            type: "Polygon",
            coordinates: [[...editing.ring, editing.ring[0]]],
        };
        onUpdate(editing.id, geometry);
        clearEditing();
    };

    const cancelEditing = () => {
        clearEditing();
    };

    const beginEditing = (feature: maplibregl.MapGeoJSONFeature) => {
        if (feature.geometry.type !== "Polygon") return;
        const coords = (feature.geometry.coordinates?.[0] ?? []) as [number, number][];
        if (coords.length < 4) return;

        // remove duplicated closing point
        const ring = coords.slice(0, -1).map((c) => [c[0], c[1]] as [number, number]);
        editingRef.current = {
            id: feature.id ?? feature.properties?.id,
            ring,
            original: feature.geometry as Geometry,
        };
        updateEditSources();
    };

    const isModifierPressed = (e?: maplibregl.MapLayerMouseEvent | maplibregl.MapMouseEvent) => {
        const oe = e?.originalEvent as MouseEvent | undefined;
        return (
            modifierRef.current.ctrl ||
            modifierRef.current.meta ||
            !!oe?.ctrlKey ||
            !!oe?.metaKey
        );
    };

    const bindEditEvents = (map: maplibregl.Map) => {
        const onHandleDown = (e: maplibregl.MapLayerMouseEvent) => {
            if (!editingRef.current) return;
            const feature = e.features?.[0];
            const idx = feature?.properties?.idx;
            if (idx === undefined) return;
            e.preventDefault();
            dragStateRef.current = { idx };
            map.getCanvas().style.cursor = "grabbing";
            map.dragPan.disable();
        };

        const onHandleMove = (e: maplibregl.MapMouseEvent) => {
            const drag = dragStateRef.current;
            const editing = editingRef.current;
            if (!drag || !editing) return;

            editing.ring[drag.idx] = [e.lngLat.lng, e.lngLat.lat];
            updateEditSources();
        };

        const stopDragging = () => {
            dragStateRef.current = null;
            map.getCanvas().style.cursor = "";
            map.dragPan.enable();
        };

        const onKeyDown = (e: KeyboardEvent) => {
            if (e.key === "Control") {
                modifierRef.current.ctrl = true;
            } else if (e.key === "Meta") {
                modifierRef.current.meta = true;
            }
            if (!editingRef.current) return;
            if (e.key === "Enter") {
                finishEditing();
            } else if (e.key === "Escape") {
                cancelEditing();
            }
        };

        const onKeyUp = (e: KeyboardEvent) => {
            if (e.key === "Control") {
                modifierRef.current.ctrl = false;
            } else if (e.key === "Meta") {
                modifierRef.current.meta = false;
            }
        };

        const onInsertHandle = (e: maplibregl.MapLayerMouseEvent) => {
            if (!editingRef.current) return;
            if (!isModifierPressed(e)) return;
            e.preventDefault();
            const editing = editingRef.current;
            const ring = editing.ring;
            const click = [e.lngLat.lng, e.lngLat.lat] as [number, number];
            let nearestIdx = 0;
            let bestDist = Number.POSITIVE_INFINITY;
            ring.forEach((pt, idx) => {
                const dx = pt[0] - click[0];
                const dy = pt[1] - click[1];
                const d = dx * dx + dy * dy; // Dùng khoảng cách Euclid bình phương để so sánh nhanh, không cần sqrt.
                if (d < bestDist) {
                    bestDist = d;
                    nearestIdx = idx;
                }
            });
            const insertIdx = nearestIdx + 1;
            ring.splice(insertIdx, 0, click);
            dragStateRef.current = { idx: insertIdx };
            map.getCanvas().style.cursor = "grabbing";
            map.dragPan.disable();
            updateEditSources();
        };

        const onCanvasLeave = () => {
            stopDragging();
        };

        map.on("mousedown", "edit-handles-circle", onHandleDown);
        map.on("mousedown", "edit-shape-line", onInsertHandle);
        map.on("mousemove", onHandleMove);
        map.on("mouseup", stopDragging);
        document.addEventListener("keydown", onKeyDown);
        document.addEventListener("keyup", onKeyUp);
        map.getCanvas().addEventListener("mouseleave", onCanvasLeave);

        map.on("remove", () => {
            map.off("mousedown", "edit-handles-circle", onHandleDown);
            map.off("mousedown", "edit-shape-line", onInsertHandle);
            map.off("mousemove", onHandleMove);
            map.off("mouseup", stopDragging);
            document.removeEventListener("keydown", onKeyDown);
            document.removeEventListener("keyup", onKeyUp);
            map.getCanvas().removeEventListener("mouseleave", onCanvasLeave);
        });
    };

    return {
        beginEditing,
        clearEditing,
        bindEditEvents,
        updateEditSources,
        editingRef,
        dragStateRef,
    };
}