/**
 * AddToWorkspaceDialog — lightweight multi-select picker for appending
 * new panes into the active workspace. Visually matches QuickSwitcher
 * (fixed top overlay, same header / row chrome) but with checkmarks on
 * the right and a thin footer to commit the selection.
 */
import { Check, Search, Terminal } from 'lucide-react';
import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react';
import { Host } from '../../types';
import { DistroAvatar } from '../DistroAvatar';
import { Button } from '../ui/button';
import { Input } from '../ui/input';
import {
  VariableSizeVirtualList,
  type VariableSizeVirtualListHandle,
} from '../ui/VariableSizeVirtualList';
import { clampListIndex, stepListIndex } from '../ui/virtualListMath';

export type AddTarget =
  | { kind: 'local' }
  | { kind: 'host'; host: Host };

interface AddToWorkspaceDialogProps {
  open: boolean;
  onOpenChange: (open: boolean) => void;
  hosts: Host[];
  workspaceTitle?: string;
  onAdd: (targets: AddTarget[]) => void;
}

const LOCAL_ITEM_ID = '__local-terminal__';
const ADD_WS_ROW_HEIGHT = 44;
const ADD_WS_HEADER_HEIGHT = 32;
const ADD_WS_HINT_HEIGHT = 36;

type Item =
  | { type: 'local'; id: typeof LOCAL_ITEM_ID }
  | { type: 'host'; id: string; host: Host };

type VisualRow =
  | { kind: 'hint'; key: string }
  | { kind: 'header'; key: string; label: string }
  | { kind: 'item'; key: string; item: Item; itemIndex: number };

export function shouldToggleWorkspaceTarget(
  key: string,
  query: string,
  metaKey: boolean,
  ctrlKey: boolean,
): boolean {
  if (metaKey || ctrlKey) return false;
  return key === 'Enter' || (key === ' ' && query.length === 0);
}

export function getWorkspaceTargetRowStateClass(
  isCursor: boolean,
  isChecked: boolean,
): string {
  if (isCursor && isChecked) return 'bg-primary/20';
  if (isCursor) return 'bg-primary/15';
  if (isChecked) return 'bg-primary/10';
  return 'hover:bg-muted/50';
}

export const AddToWorkspaceDialog: React.FC<AddToWorkspaceDialogProps> = ({
  open,
  onOpenChange,
  hosts,
  workspaceTitle,
  onAdd,
}) => {
  const [query, setQuery] = useState('');
  const [selected, setSelected] = useState<Set<string>>(new Set());
  const [selectedIndex, setSelectedIndex] = useState(0);
  const inputRef = useRef<HTMLInputElement>(null);
  const containerRef = useRef<HTMLDivElement>(null);
  const listRef = useRef<VariableSizeVirtualListHandle>(null);

  // Reset on open + auto-focus the search input.
  useEffect(() => {
    if (!open) return;
    setQuery('');
    setSelected(new Set());
    setSelectedIndex(0);
    const timer = window.setTimeout(() => inputRef.current?.focus(), 40);
    return () => window.clearTimeout(timer);
  }, [open]);

  // Close on click outside.
  useEffect(() => {
    if (!open) return;
    const handler = (e: MouseEvent) => {
      if (containerRef.current && !containerRef.current.contains(e.target as Node)) {
        onOpenChange(false);
      }
    };
    document.addEventListener('mousedown', handler);
    return () => document.removeEventListener('mousedown', handler);
  }, [open, onOpenChange]);

  // NOTE: no serial filter here — callers decide which subset of
  // hosts to pass based on mode. `appendHostToWorkspace` cannot build
  // a serial session, so append mode passes non-serial hosts only;
  // `createWorkspaceFromTargets` handles serial explicitly, so create
  // mode passes everything.
  const selectableHosts = hosts;

  const localMatches = useMemo(() => {
    const term = query.trim().toLowerCase();
    if (!term) return true;
    return 'local terminal localhost'.includes(term);
  }, [query]);

  const filteredHosts = useMemo(() => {
    const term = query.trim().toLowerCase();
    if (!term) return selectableHosts;
    return selectableHosts.filter((h) =>
      (h.label?.toLowerCase().includes(term))
      || (h.hostname?.toLowerCase().includes(term))
      || (h.username?.toLowerCase().includes(term))
      || (h.group?.toLowerCase().includes(term)),
    );
  }, [selectableHosts, query]);

  const { items, visualRows, itemIndexToVisualIndex } = useMemo(() => {
    const list: Item[] = [];
    const visual: VisualRow[] = [{ kind: 'hint', key: 'hint' }];
    const itemToVisual = new Map<number, number>();

    const pushHeader = (key: string, label: string) => {
      visual.push({ kind: 'header', key, label });
    };
    const pushItem = (item: Item) => {
      const itemIndex = list.length;
      list.push(item);
      itemToVisual.set(itemIndex, visual.length);
      visual.push({ kind: 'item', key: item.id, item, itemIndex });
    };

    if (localMatches) {
      pushHeader('header:local', 'Local Shells');
      pushItem({ type: 'local', id: LOCAL_ITEM_ID });
    }
    if (filteredHosts.length > 0) {
      pushHeader('header:hosts', 'Hosts');
      for (const host of filteredHosts) {
        pushItem({ type: 'host', id: host.id, host });
      }
    }

    return { items: list, visualRows: visual, itemIndexToVisualIndex: itemToVisual };
  }, [filteredHosts, localMatches]);

  useEffect(() => {
    if (!open) return;
    setSelectedIndex((prev) => clampListIndex(prev, items.length));
  }, [items.length, open]);

  useEffect(() => {
    if (!open) return;
    const visualIndex = itemIndexToVisualIndex.get(selectedIndex);
    if (visualIndex === undefined) return;
    listRef.current?.scrollToIndex(visualIndex, 'auto');
  }, [itemIndexToVisualIndex, open, selectedIndex]);

  const toggle = useCallback((id: string) => {
    setSelected((prev) => {
      const next = new Set(prev);
      if (next.has(id)) next.delete(id); else next.add(id);
      return next;
    });
  }, []);

  const handleTargetClick = useCallback((index: number, id: string) => {
    setSelectedIndex(index);
    toggle(id);
    inputRef.current?.focus();
  }, [toggle]);

  const handleCommit = () => {
    if (selected.size === 0) return;
    const targets: AddTarget[] = [];
    if (selected.has(LOCAL_ITEM_ID)) targets.push({ kind: 'local' });
    for (const host of selectableHosts) {
      if (selected.has(host.id)) targets.push({ kind: 'host', host });
    }
    if (targets.length === 0) return;
    onAdd(targets);
    onOpenChange(false);
  };

  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === 'Escape') {
      e.preventDefault();
      onOpenChange(false);
      return;
    }
    if (e.key === 'ArrowDown') {
      e.preventDefault();
      setSelectedIndex((i) => stepListIndex(i, items.length, 1));
    } else if (e.key === 'ArrowUp') {
      e.preventDefault();
      setSelectedIndex((i) => stepListIndex(i, items.length, -1));
    } else if (shouldToggleWorkspaceTarget(e.key, query, e.metaKey, e.ctrlKey)) {
      if (items.length === 0) return;
      e.preventDefault();
      const item = items[clampListIndex(selectedIndex, items.length)];
      if (!item) return;
      toggle(item.id);
    } else if (e.key === 'Enter' && (e.metaKey || e.ctrlKey)) {
      e.preventDefault();
      handleCommit();
    }
  };

  const getRowHeight = useCallback((row: VisualRow) => {
    if (row.kind === 'hint') return ADD_WS_HINT_HEIGHT;
    if (row.kind === 'header') return ADD_WS_HEADER_HEIGHT;
    return ADD_WS_ROW_HEIGHT;
  }, []);

  const renderRow = useCallback((row: VisualRow) => {
    if (row.kind === 'hint') {
      return (
        <div className="px-4 py-2 flex items-center gap-2">
          <span className="text-xs text-muted-foreground">Pick one or more</span>
          <kbd className="text-[10px] text-muted-foreground bg-muted px-1 py-0.5 rounded">Space / Enter</kbd>
          <span className="text-[10px] text-muted-foreground">toggle</span>
          <kbd className="text-[10px] text-muted-foreground bg-muted px-1 py-0.5 rounded">
            {typeof navigator !== 'undefined' && /Mac|iPhone|iPad/.test(navigator.platform) ? '⌘' : 'Ctrl'}+Enter
          </kbd>
          <span className="text-[10px] text-muted-foreground">add</span>
        </div>
      );
    }
    if (row.kind === 'header') {
      return (
        <div className="flex h-full items-end px-4 pb-1.5">
          <span className="text-xs font-medium text-muted-foreground">{row.label}</span>
        </div>
      );
    }

    const { item, itemIndex: idx } = row;
    const isCursor = idx === selectedIndex;
    const isChecked = selected.has(item.id);

    if (item.type === 'local') {
      return (
        <div
          className={`flex h-full min-h-0 items-center gap-3 overflow-hidden px-4 py-2.5 cursor-pointer transition-colors ${getWorkspaceTargetRowStateClass(isCursor, isChecked)}`}
          onClick={() => handleTargetClick(idx, LOCAL_ITEM_ID)}
        >
          <div className="flex h-6 w-6 shrink-0 items-center justify-center rounded text-muted-foreground">
            <Terminal size={16} />
          </div>
          <span className="min-w-0 flex-1 truncate text-sm font-medium">Local Terminal</span>
          {isChecked && <Check size={14} className="text-primary shrink-0" />}
        </div>
      );
    }

    const host = item.host;
    return (
      <div
        className={`flex h-full min-h-0 items-center justify-between overflow-hidden px-4 py-2.5 cursor-pointer transition-colors ${getWorkspaceTargetRowStateClass(isCursor, isChecked)}`}
        onClick={() => handleTargetClick(idx, host.id)}
      >
        <div className="flex min-w-0 items-center gap-3">
          <DistroAvatar host={host} fallback={(host.label || host.hostname).slice(0, 2).toUpperCase()} size="sm" />
          <span className="truncate text-sm font-medium">{host.label || host.hostname}</span>
        </div>
        <div className="ml-2 flex min-w-0 shrink-0 items-center gap-2">
          <div className="max-w-[12rem] truncate text-[11px] text-muted-foreground">
            {host.group ? `Personal / ${host.group}` : 'Personal'}
          </div>
          {isChecked && <Check size={14} className="text-primary shrink-0" />}
        </div>
      </div>
    );
  }, [handleTargetClick, selected, selectedIndex]);

  if (!open) return null;

  const count = selected.size;

  return (
    <div
      className="fixed inset-x-0 top-12 z-50 flex justify-center pt-2"
      style={{ pointerEvents: 'none' }}
    >
      <div
        ref={containerRef}
        className="w-full max-w-2xl mx-4 bg-background border border-border rounded-xl shadow-2xl overflow-hidden max-h-[520px] flex flex-col"
        style={{ pointerEvents: 'auto' }}
      >
        {/* Search header — mirrors QuickSwitcher chrome. */}
        <div className="flex items-center gap-3 px-4 py-3 border-b border-border">
          <Search size={16} className="text-muted-foreground" />
          <Input
            ref={inputRef}
            value={query}
            onChange={(e) => {
              setQuery(e.target.value);
              setSelectedIndex(0);
            }}
            onKeyDown={handleKeyDown}
            placeholder="Search hosts or local shells..."
            className="flex-1 h-8 border-0 bg-transparent focus-visible:ring-0 focus-visible:ring-offset-0 px-0 text-sm"
          />
          {workspaceTitle && (
            <span className="text-[11px] text-muted-foreground truncate max-w-[180px]">
              {workspaceTitle}
            </span>
          )}
        </div>

        {/*
          Same max-h flex trap as Quick Switcher: list must not grow with the virtual
          spacer or hosts below the first screen become unreachable.
        */}
        <div className="min-h-0 flex-1 overflow-hidden" data-host-picker-virtual="add-workspace">
          {items.length === 0 ? (
            <div className="px-4 py-8 text-center text-xs text-muted-foreground">
              No matches
            </div>
          ) : (
            <VariableSizeVirtualList<VisualRow>
              ref={listRef}
              items={visualRows}
              getItemHeight={getRowHeight}
              className="h-full max-h-[min(360px,calc(100vh-14rem))]"
              overscan={8}
              getItemKey={(row) => row.key}
              renderItem={renderRow}
            />
          )}
        </div>

        {/* Slim footer to commit. Kept minimal so the layout feels like
            QuickSwitcher's chrome with a single action strip tacked on. */}
        <div className="flex items-center justify-end gap-2 px-3 py-2 border-t border-border">
          <Button variant="ghost" size="sm" onClick={() => onOpenChange(false)}>
            Cancel
          </Button>
          <Button size="sm" disabled={count === 0} onClick={handleCommit}>
            {count === 0 ? 'Add' : `Add ${count}`}
          </Button>
        </div>
      </div>
    </div>
  );
};

export default AddToWorkspaceDialog;