// components/generic/Sheet/AddUsersSheet.jsx

import { useState, useEffect, useMemo } from "react";
import { Sheet, SheetContent, SheetHeader, SheetTitle } from "@/components/ui/sheet";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { ScrollArea, ScrollBar } from "@/components/ui/scroll-area";
import { Spinner } from "@/components/ui/spinner";
import { AlertTriangle } from "lucide-react";

/**
 * Generic sheet for selecting and adding users to any entity
 * (groups, tasks, projects, etc.)
 *
 * @param {Object}    props
 * @param {boolean}   props.open
 * @param {Function}  props.onOpenChange
 *
 * @param {string}    [props.title]          Sheet heading. Default: "Add members"
 * @param {string}    [props.submitLabel]    Submit button label. Default: "Add"
 *
 * @param {Array}     props.users            [{ [idKey], [labelKey] }] — list to display
 * @param {boolean}   props.loading
 * @param {Function}  props.onFetch          Called on open to (re)load the list
 *
 * @param {string}    [props.idKey]          Key for the user id.    Default: "user_id"
 * @param {string}    [props.labelKey]       Key for the display name. Default: "full_name"
 * @param {string}    [props.subLabelKey]    Optional secondary line (e.g. "email")
 * @param {string}    [props.warningKey]     If set, users with a truthy value at this key show
 *                                           a "will be moved" warning (e.g. "current_group")
 *
 * @param {Function}  props.onSubmit         Called with selected ids[]
 *
 * @example — groups
 * <AddUsersSheet
 *   title="Add members"
 *   users={usersNotIn}
 *   onFetch={() => fetchUsersNotInGroup(gid)}
 *   onSubmit={(ids) => addUsersToGroup(gid, ids)}
 *   ...
 * />
 *
 * @example — tasks
 * <AddUsersSheet
 *   title="Assign users"
 *   users={unassignedUsers}
 *   onFetch={() => fetchUnassignedUsers(taskId)}
 *   onSubmit={(ids) => assignUsersToTask(taskId, ids)}
 *   idKey="user_id"
 *   labelKey="full_name"
 *   subLabelKey="email"
 *   ...
 * />
 */
export function AddSheet({
    open,
    onOpenChange,

    title = "Add members",
    submitLabel = "Add",

    users = [],
    loading = false,
    onFetch,

    idKey = "user_id",
    labelKey = "full_name",
    subLabelKey = null,
    warningKey = null,

    onSubmit,
}) {
    const [search, setSearch] = useState("");
    const [selected, setSelected] = useState([]);

    useEffect(() => {
        if (open) {
            onFetch?.();
            setSearch("");
            setSelected([]);
        }
    }, [open]);

    const filtered = useMemo(() => {
        if (!search.trim()) return users;
        return users.filter((u) =>
            String(u[labelKey] ?? "").toLowerCase().includes(search.toLowerCase())
        );
    }, [search, users, labelKey]);

    const toggle = (id) =>
        setSelected((prev) =>
            prev.includes(id) ? prev.filter((v) => v !== id) : [...prev, id]
        );

    const toggleAll = () => {
        const allIds = filtered.map((u) => u[idKey]);
        const allSelected = allIds.every((id) => selected.includes(id));
        setSelected((prev) =>
            allSelected
                ? prev.filter((id) => !allIds.includes(id))
                : [...new Set([...prev, ...allIds])]
        );
    };

    const allFilteredSelected =
        filtered.length > 0 && filtered.every((u) => selected.includes(u[idKey]));

    const movingCount = useMemo(() => {
        if (!warningKey) return 0;
        return selected.filter((id) => {
            const user = users.find((u) => u[idKey] === id);
            return !!user?.[warningKey];
        }).length;
    }, [selected, users, warningKey, idKey]);

    async function handleSubmit() {
        if (!selected.length) return;
        await onSubmit(selected);
        onOpenChange(false);
    }

    function handleClose() {
        setSearch("");
        setSelected([]);
        onOpenChange(false);
    }

    return (
        <Sheet open={open} onOpenChange={handleClose}>
            {/*
                SheetContent is a flex column with fixed height (100dvh).
                We split it into 3 rows: header (shrink-0), body (flex-1 overflow-hidden), footer (shrink-0).
                The body itself is a flex column — search and select-all shrink, list overflows.
            */}
            <SheetContent side="right" className="w-[400px] flex flex-col h-full p-0">

                {/* Header */}
                <SheetHeader className="shrink-0 border-b px-6 py-4">
                    <SheetTitle>{title}</SheetTitle>
                </SheetHeader>

                {/* Body — fills remaining space, clips overflow */}
                <div className="flex-1 min-h-0 flex flex-col gap-3 px-6 py-4 relative">
                    {loading && (
                        <div className="absolute inset-0 flex items-center justify-center bg-background/60 backdrop-blur-sm z-10">
                            <Spinner className="size-8" />
                        </div>
                    )}

                    {/* Search — fixed height */}
                    <div className="shrink-0">
                        <Input
                            placeholder="Search..."
                            value={search}
                            onChange={(e) => setSearch(e.target.value)}
                        />
                    </div>

                    {/* Select all — fixed height */}
                    {filtered.length > 0 && (
                        <label className="shrink-0 flex items-center gap-2 text-sm font-medium cursor-pointer select-none border-b pb-3">
                            <input
                                type="checkbox"
                                checked={allFilteredSelected}
                                onChange={toggleAll}
                            />
                            Select all ({filtered.length})
                        </label>
                    )}

                    {/* Scrollable list — takes all remaining space */}
                    <div className="flex-1 min-h-0 overflow-y-auto">
                        <div className="space-y-1 pr-1">
                            {!loading && filtered.length === 0 ? (
                                <p className="text-sm text-muted-foreground text-center py-6">
                                    {search ? `No results for "${search}".` : "No users available."}
                                </p>
                            ) : (
                                filtered.map((user) => {
                                    const id      = user[idKey];
                                    const label   = user[labelKey];
                                    const sub     = subLabelKey ? user[subLabelKey] : null;
                                    const warning = warningKey  ? user[warningKey]  : null;

                                    return (
                                        <label
                                            key={id}
                                            className="flex items-center gap-3 p-1 rounded-md hover:bg-muted cursor-pointer text-sm select-none"
                                        >
                                            <input
                                                type="checkbox"
                                                checked={selected.includes(id)}
                                                onChange={() => toggle(id)}
                                            />
                                            <div className="flex flex-col min-w-0 flex-1">
                                                <span className="truncate">{label}</span>
                                                {sub && (
                                                    <span className="text-xs text-muted-foreground truncate">
                                                        {sub}
                                                    </span>
                                                )}
                                                {warning && (
                                                    <span className="text-xs text-amber-600 flex items-center gap-1 mt-0.5">
                                                        <AlertTriangle className="size-3 shrink-0" />
                                                        Also in: {warning}
                                                    </span>
                                                )}
                                            </div>
                                        </label>
                                    );
                                })
                            )}
                        </div>
                    </div>
                </div>

                {/* Footer */}
                <div className="shrink-0 flex flex-col gap-2 border-t px-6 py-4">
                    {movingCount > 0 && (
                        <p className="text-xs text-amber-600 flex items-center gap-1.5">
                            <AlertTriangle className="size-3 shrink-0" />
                            {movingCount} user{movingCount > 1 ? 's' : ''} already belong{movingCount === 1 ? 's' : ''} to other group{movingCount > 1 ? 's' : ''}.
                        </p>
                    )}
                    <div className="flex gap-2">
                        <Button variant="outline" className="flex-1" onClick={handleClose}>
                            Cancel
                        </Button>
                        <Button
                            className="flex-1"
                            disabled={!selected.length || loading}
                            onClick={handleSubmit}
                        >
                            {selected.length > 0 ? `${submitLabel} (${selected.length})` : submitLabel}
                        </Button>
                    </div>
                </div>

            </SheetContent>
        </Sheet>
    );
}