import { useState } from 'react'
import { Button } from '@/components/ui/button'
import { Input } from '@/components/ui/input'
import { Textarea } from '@/components/ui/textarea'
import { Label } from '@/components/ui/label'
import { Trash2, Plus, ChevronUp, ChevronDown } from 'lucide-react'

interface TemplateItemRow {
  id: string
  title: string
  description: string
}

interface TemplateSectionRow {
  id: string
  title: string
  description: string
  items: TemplateItemRow[]
}

interface Props {
  sections: TemplateSectionRow[]
  onChange: (sections: TemplateSectionRow[]) => void
}

function uid() {
  return Math.random().toString(36).slice(2)
}

export function TemplateSectionBuilder({ sections, onChange }: Props) {
  function addSection() {
    onChange([...sections, { id: uid(), title: '', description: '', items: [] }])
  }

  function removeSection(idx: number) {
    onChange(sections.filter((_, i) => i !== idx))
  }

  function moveSection(idx: number, dir: -1 | 1) {
    const next = [...sections]
    const [removed] = next.splice(idx, 1)
    next.splice(idx + dir, 0, removed)
    onChange(next)
  }

  function updateSection(idx: number, field: 'title' | 'description', value: string) {
    onChange(sections.map((s, i) => (i === idx ? { ...s, [field]: value } : s)))
  }

  function addItem(sIdx: number) {
    onChange(sections.map((s, i) =>
      i === sIdx ? { ...s, items: [...s.items, { id: uid(), title: '', description: '' }] } : s,
    ))
  }

  function removeItem(sIdx: number, iIdx: number) {
    onChange(sections.map((s, i) =>
      i === sIdx ? { ...s, items: s.items.filter((_, j) => j !== iIdx) } : s,
    ))
  }

  function moveItem(sIdx: number, iIdx: number, dir: -1 | 1) {
    onChange(sections.map((s, i) => {
      if (i !== sIdx) return s
      const next = [...s.items]
      const [removed] = next.splice(iIdx, 1)
      next.splice(iIdx + dir, 0, removed)
      return { ...s, items: next }
    }))
  }

  function updateItem(sIdx: number, iIdx: number, field: 'title' | 'description', value: string) {
    onChange(sections.map((s, i) =>
      i === sIdx
        ? { ...s, items: s.items.map((item, j) => (j === iIdx ? { ...item, [field]: value } : item)) }
        : s,
    ))
  }

  return (
    <div className="space-y-4">
      {sections.map((section, sIdx) => (
        <div key={section.id} className="border rounded-lg overflow-hidden">
          <div className="bg-muted/40 px-3 py-2 flex items-center gap-2">
            <div className="flex flex-col gap-0.5">
              <Button type="button" variant="ghost" size="icon" className="h-4 w-4" disabled={sIdx === 0} onClick={() => moveSection(sIdx, -1)}>
                <ChevronUp className="h-3 w-3" />
              </Button>
              <Button type="button" variant="ghost" size="icon" className="h-4 w-4" disabled={sIdx === sections.length - 1} onClick={() => moveSection(sIdx, 1)}>
                <ChevronDown className="h-3 w-3" />
              </Button>
            </div>
            <Input
              className="h-7 text-sm font-medium flex-1"
              placeholder="Section title *"
              value={section.title}
              onChange={(e) => updateSection(sIdx, 'title', e.target.value)}
              required
            />
            <Button type="button" variant="ghost" size="icon" className="h-7 w-7" onClick={() => removeSection(sIdx)}>
              <Trash2 className="h-4 w-4 text-destructive" />
            </Button>
          </div>

          <div className="p-3 space-y-2">
            <Textarea
              className="text-xs resize-none"
              placeholder="Section description (optional)"
              rows={1}
              value={section.description}
              onChange={(e) => updateSection(sIdx, 'description', e.target.value)}
            />

            <div className="space-y-1.5">
              {section.items.map((item, iIdx) => (
                <div key={item.id} className="flex items-center gap-2">
                  <div className="flex flex-col gap-0.5">
                    <Button type="button" variant="ghost" size="icon" className="h-4 w-4" disabled={iIdx === 0} onClick={() => moveItem(sIdx, iIdx, -1)}>
                      <ChevronUp className="h-3 w-3" />
                    </Button>
                    <Button type="button" variant="ghost" size="icon" className="h-4 w-4" disabled={iIdx === section.items.length - 1} onClick={() => moveItem(sIdx, iIdx, 1)}>
                      <ChevronDown className="h-3 w-3" />
                    </Button>
                  </div>
                  <Input
                    className="h-7 text-xs flex-1"
                    placeholder="Item title *"
                    value={item.title}
                    onChange={(e) => updateItem(sIdx, iIdx, 'title', e.target.value)}
                    required
                  />
                  <Input
                    className="h-7 text-xs flex-1"
                    placeholder="Description (optional)"
                    value={item.description}
                    onChange={(e) => updateItem(sIdx, iIdx, 'description', e.target.value)}
                  />
                  <Button type="button" variant="ghost" size="icon" className="h-7 w-7 shrink-0" onClick={() => removeItem(sIdx, iIdx)}>
                    <Trash2 className="h-3 w-3 text-destructive" />
                  </Button>
                </div>
              ))}
            </div>

            <Button type="button" variant="outline" size="sm" className="text-xs h-7" onClick={() => addItem(sIdx)}>
              <Plus className="h-3 w-3 mr-1" />Add Item
            </Button>
          </div>
        </div>
      ))}

      <Button type="button" variant="outline" size="sm" onClick={addSection}>
        <Plus className="h-4 w-4 mr-1" />Add Section
      </Button>

      {sections.length === 0 && (
        <p className="text-sm text-muted-foreground text-center py-2">No sections yet — add one above.</p>
      )}
    </div>
  )
}

export type { TemplateSectionRow, TemplateItemRow }