'use client'

import { useCallback, useEffect, useState } from 'react'
import { GridLayout, useContainerWidth, type LayoutItem } from 'react-grid-layout'
import 'react-grid-layout/css/styles.css'

import { useAuth } from '@/contexts/auth-context'
import { dashboard, type WidgetLayoutItem } from '@/lib/api/dashboard'
import { WIDGET_REGISTRY } from '@/lib/widgets/registry'
import { ROLE_DEFAULT_LAYOUTS } from '@/lib/widgets/defaults'
import { getApiError } from '@/lib/api'
import { toast } from '@/components/ui/toast'
import { WidgetContainer } from './widget-container'
import { WidgetPicker } from './widget-picker'
import { Button } from '@/components/ui/button'
import { Skeleton } from '@/components/ui/skeleton'
import { HugeiconsIcon } from '@hugeicons/react'
import {
  PencilEdit01Icon,
  Tick02Icon,
  Cancel01Icon,
  Add01Icon,
  Refresh01Icon,
} from '@hugeicons/core-free-icons'

// ─── Layout helpers ───────────────────────────────────────────────────────────

function toGridItems(items: WidgetLayoutItem[], editable: boolean): LayoutItem[] {
  return items.map(item => {
    const def = WIDGET_REGISTRY[item.widgetType]
    return {
      i: item.i,
      x: item.x,
      y: item.y,
      w: item.w,
      h: item.h,
      minW: def?.minW ?? 2,
      minH: def?.minH ?? 2,
      ...(def?.maxW ? { maxW: def.maxW } : {}),
      isDraggable: editable,
      isResizable: editable,
    }
  })
}

function applyGridChanges(updated: readonly LayoutItem[], current: WidgetLayoutItem[]): WidgetLayoutItem[] {
  const typeMap = Object.fromEntries(current.map(item => [item.i, item.widgetType]))
  return updated
    .filter(l => typeMap[l.i])
    .map(l => ({ i: l.i, widgetType: typeMap[l.i], x: l.x, y: l.y, w: l.w, h: l.h }))
}

// ─── Component ────────────────────────────────────────────────────────────────

export function DashboardCanvas() {
  const { user } = useAuth()
  const { width, containerRef } = useContainerWidth()

  const [savedLayout, setSavedLayout] = useState<WidgetLayoutItem[]>([])
  const [editingLayout, setEditingLayout] = useState<WidgetLayoutItem[]>([])
  const [isEditing, setIsEditing] = useState(false)
  const [isLoading, setIsLoading] = useState(true)
  const [isSaving, setIsSaving] = useState(false)
  const [pickerOpen, setPickerOpen] = useState(false)

  const roleDefault = ROLE_DEFAULT_LAYOUTS[user.role] ?? []

  // ─── Load ──────────────────────────────────────────────────────────────────

  const loadPreferences = useCallback(async () => {
    setIsLoading(true)
    try {
      const res = await dashboard.getPreferences()
      setSavedLayout(res.layout)
    } catch {
      setSavedLayout(roleDefault)
    } finally {
      setIsLoading(false)
    }
  // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [user.role])

  useEffect(() => { loadPreferences() }, [loadPreferences])

  // ─── Edit mode ─────────────────────────────────────────────────────────────

  function startEditing() {
    setEditingLayout([...savedLayout])
    setIsEditing(true)
  }

  function cancelEditing() {
    setEditingLayout([])
    setIsEditing(false)
  }

  async function saveLayout() {
    setIsSaving(true)
    try {
      await dashboard.savePreferences(editingLayout)
      setSavedLayout(editingLayout)
      setIsEditing(false)
      toast.add({ title: 'Dashboard saved', type: 'success' })
    } catch (err) {
      toast.add({ title: 'Failed to save', description: getApiError(err), type: 'error' })
    } finally {
      setIsSaving(false)
    }
  }

  function resetToDefaults() {
    setEditingLayout([...roleDefault])
  }

  // ─── Grid mutations ────────────────────────────────────────────────────────

  function onGridChange(updated: readonly LayoutItem[]) {
    if (!isEditing) return
    setEditingLayout(prev => applyGridChanges(updated, prev))
  }

  function removeWidget(id: string) {
    setEditingLayout(prev => prev.filter(item => item.i !== id))
  }

  function addWidget(widgetType: string) {
    const def = WIDGET_REGISTRY[widgetType]
    if (!def) return
    const newItem: WidgetLayoutItem = {
      i: `${widgetType}-${Date.now()}`,
      widgetType,
      x: 0,
      y: Infinity,
      w: def.defaultW,
      h: def.defaultH,
    }
    setEditingLayout(prev => [...prev, newItem])
  }

  // ─── Render ────────────────────────────────────────────────────────────────

  const activeLayout = isEditing ? editingLayout : savedLayout

  if (isLoading) {
    return (
      <div className="flex flex-col gap-4">
        <div className="flex items-center justify-between">
          <div className="flex flex-col gap-1.5">
            <Skeleton className="h-7 w-28" />
            <Skeleton className="h-4 w-48" />
          </div>
          <Skeleton className="h-9 w-24" />
        </div>
        <div className="grid grid-cols-3 gap-3">
          {Array.from({ length: 6 }).map((_, i) => (
            <Skeleton key={i} className="h-48" />
          ))}
        </div>
      </div>
    )
  }

  return (
    <div className="flex flex-col gap-4">
      {/* Header */}
      <div className="flex items-center justify-between gap-2">
        <div>
          <h1 className="text-2xl font-semibold text-foreground">Dashboard</h1>
          <p className="text-sm text-muted-foreground">
            {isEditing
              ? 'Drag to reposition · Resize from the corner · Add or remove widgets'
              : `Welcome back, ${user.fullName}`}
          </p>
        </div>
        <div className="flex items-center gap-2">
          {isEditing ? (
            <>
              <Button variant="outline" size="sm" onClick={resetToDefaults} disabled={isSaving}>
                <HugeiconsIcon icon={Refresh01Icon} size={14} strokeWidth={2} />
                Reset
              </Button>
              <Button variant="outline" size="sm" onClick={() => setPickerOpen(true)} disabled={isSaving}>
                <HugeiconsIcon icon={Add01Icon} size={14} strokeWidth={2} />
                Add widget
              </Button>
              <Button variant="outline" size="sm" onClick={cancelEditing} disabled={isSaving}>
                <HugeiconsIcon icon={Cancel01Icon} size={14} strokeWidth={2} />
                Cancel
              </Button>
              <Button size="sm" onClick={saveLayout} disabled={isSaving}>
                <HugeiconsIcon icon={Tick02Icon} size={14} strokeWidth={2} />
                {isSaving ? 'Saving…' : 'Save'}
              </Button>
            </>
          ) : (
            <Button variant="outline" size="sm" onClick={startEditing}>
              <HugeiconsIcon icon={PencilEdit01Icon} size={14} strokeWidth={2} />
              Customize
            </Button>
          )}
        </div>
      </div>

      {/* Grid */}
      {activeLayout.length === 0 ? (
        <div className="flex flex-col items-center justify-center rounded-2xl border border-dashed py-20 text-center">
          <p className="text-sm font-medium text-foreground">Your dashboard is empty</p>
          <p className="mt-1 text-sm text-muted-foreground">
            Click Customize, then Add widget to get started.
          </p>
          {!isEditing && (
            <Button variant="outline" size="sm" className="mt-4" onClick={startEditing}>
              <HugeiconsIcon icon={PencilEdit01Icon} size={14} strokeWidth={2} />
              Customize
            </Button>
          )}
        </div>
      ) : (
        <div ref={containerRef}>
          <GridLayout
            width={width}
            layout={toGridItems(activeLayout, isEditing)}
            gridConfig={{ cols: 12, rowHeight: 80, margin: [12, 12] as const }}
            dragConfig={{ handle: '.drag-handle' }}
            resizeConfig={{ handles: ['se'] as const }}
            onLayoutChange={onGridChange}
            className="relative"
          >
            {activeLayout.map(item => (
              <div key={item.i}>
                <WidgetContainer
                  widgetType={item.widgetType}
                  editMode={isEditing}
                  onRemove={() => removeWidget(item.i)}
                />
              </div>
            ))}
          </GridLayout>
        </div>
      )}

      {/* Widget Picker */}
      <WidgetPicker
        open={pickerOpen}
        onClose={() => setPickerOpen(false)}
        role={user.role}
        currentLayout={editingLayout}
        onAdd={addWidget}
      />
    </div>
  )
}