"use client"

import { useState, useEffect, useRef } from "react"
import { Button } from "@/components/ui/button"
import { Heart, Sparkles, TrendingUp } from "lucide-react"

interface Props {
  onSelect: (amountPence: number) => void
  eventName: string
  eventId?: string
}

interface AiSuggestion {
  amounts: number[]
  nudge: string
  socialProof: string
}

const FALLBACK_AMOUNTS = [2000, 5000, 10000, 25000, 50000, 100000]

export function AmountStep({ onSelect, eventName, eventId }: Props) {
  const [custom, setCustom] = useState("")
  const [selected, setSelected] = useState<number | null>(null)
  const [suggestions, setSuggestions] = useState<AiSuggestion | null>(null)
  const [hovering, setHovering] = useState<number | null>(null)
  const inputRef = useRef<HTMLInputElement>(null)

  // Fetch AI-powered suggestions
  useEffect(() => {
    const url = eventId ? `/api/ai/suggest?eventId=${eventId}` : "/api/ai/suggest"
    fetch(url)
      .then(r => r.json())
      .then(data => {
        if (data.amounts?.length) setSuggestions(data)
      })
      .catch(() => {})
  }, [eventId])

  const amounts = suggestions?.amounts || FALLBACK_AMOUNTS

  const handlePreset = (amount: number) => {
    setSelected(amount)
    setCustom("")
    // Haptic feedback on mobile
    if (navigator.vibrate) navigator.vibrate(10)
  }

  const handleCustomChange = (value: string) => {
    const clean = value.replace(/[^0-9.]/g, "")
    setCustom(clean)
    setSelected(null)
  }

  const handleContinue = () => {
    const amount = selected || Math.round(parseFloat(custom) * 100)
    if (amount >= 100) onSelect(amount)
  }

  const activeAmount = selected || (custom ? Math.round(parseFloat(custom) * 100) : 0)
  const isValid = activeAmount >= 100
  const giftAidBonus = Math.round(activeAmount * 0.25)

  return (
    <div className="max-w-md mx-auto pt-2 space-y-6 animate-fade-up">
      {/* Hero */}
      <div className="text-center space-y-3">
        <div className="inline-flex items-center justify-center w-14 h-14 rounded-2xl bg-gradient-to-br from-trust-blue to-blue-600 shadow-lg shadow-trust-blue/30">
          <Heart className="h-7 w-7 text-white" />
        </div>
        <h1 className="text-3xl font-black text-gray-900 tracking-tight">
          Make a Pledge
        </h1>
        <p className="text-base text-muted-foreground">
          for <span className="font-semibold text-foreground">{eventName}</span>
        </p>
      </div>

      {/* Social proof */}
      {suggestions?.socialProof && (
        <div className="flex items-center justify-center gap-2 animate-fade-in">
          <div className="flex -space-x-2">
            {[...Array(3)].map((_, i) => (
              <div key={i} className="w-6 h-6 rounded-full bg-gradient-to-br from-trust-blue to-blue-400 border-2 border-white flex items-center justify-center">
                <span className="text-[8px] text-white font-bold">{["A", "S", "M"][i]}</span>
              </div>
            ))}
          </div>
          <p className="text-sm text-muted-foreground">
            <TrendingUp className="h-3.5 w-3.5 inline mr-1 text-success-green" />
            {suggestions.socialProof}
          </p>
        </div>
      )}

      {/* Amount grid */}
      <div className="grid grid-cols-3 gap-2.5 stagger-children">
        {amounts.map((amount) => {
          const isSelected = selected === amount
          const isHovering = hovering === amount
          const pounds = amount / 100

          return (
            <button
              key={amount}
              onClick={() => handlePreset(amount)}
              onMouseEnter={() => setHovering(amount)}
              onMouseLeave={() => setHovering(null)}
              className={`
                relative tap-target rounded-2xl border-2 py-4 text-center font-bold transition-all duration-200
                ${isSelected
                  ? "border-trust-blue bg-trust-blue text-white shadow-xl shadow-trust-blue/30 scale-[1.03]"
                  : isHovering
                    ? "border-trust-blue/40 bg-trust-blue/5 text-gray-900"
                    : "border-gray-200 bg-white text-gray-900 hover:border-trust-blue/30"
                }
              `}
            >
              <span className="text-xl">£{pounds >= 1000 ? `${pounds / 1000}k` : pounds}</span>
              {/* Gift Aid indicator */}
              {isSelected && (
                <div className="absolute -top-2 -right-2 bg-success-green text-white text-[10px] font-bold px-1.5 py-0.5 rounded-full animate-scale-in shadow-sm">
                  +£{Math.round(amount * 0.25 / 100)}
                </div>
              )}
            </button>
          )
        })}
      </div>

      {/* AI nudge */}
      {suggestions?.nudge && (
        <p className="text-center text-sm text-muted-foreground/80 italic flex items-center justify-center gap-1.5 animate-fade-in" style={{ animationDelay: "400ms" }}>
          <Sparkles className="h-3.5 w-3.5 text-warm-amber" />
          {suggestions.nudge}
        </p>
      )}

      {/* Custom amount — premium input */}
      <div className="space-y-2">
        <button
          onClick={() => inputRef.current?.focus()}
          className="text-xs font-medium text-muted-foreground hover:text-trust-blue transition-colors cursor-pointer"
        >
          Or enter your own amount →
        </button>
        <div className="relative group">
          <span className="absolute left-4 top-1/2 -translate-y-1/2 text-2xl font-black text-gray-300 group-focus-within:text-trust-blue transition-colors">£</span>
          <input
            ref={inputRef}
            type="text"
            inputMode="decimal"
            placeholder="0"
            value={custom}
            onChange={(e) => handleCustomChange(e.target.value)}
            className="w-full pl-10 pr-4 h-16 text-2xl font-black text-center rounded-2xl border-2 border-gray-200 bg-white focus:border-trust-blue focus:ring-4 focus:ring-trust-blue/10 outline-none transition-all"
          />
        </div>
      </div>

      {/* Live Gift Aid preview */}
      {isValid && (
        <div className="rounded-2xl bg-gradient-to-r from-success-green/5 to-success-green/10 border border-success-green/20 p-4 text-center animate-scale-in">
          <p className="text-sm">
            <span className="font-bold text-success-green">With Gift Aid:</span>{" "}
            your £{(activeAmount / 100).toFixed(0)} becomes{" "}
            <span className="font-black text-success-green text-lg">
              £{((activeAmount + giftAidBonus) / 100).toFixed(0)}
            </span>
          </p>
          <p className="text-xs text-muted-foreground mt-0.5">HMRC adds 25% — at zero cost to you</p>
        </div>
      )}

      {/* Continue */}
      <Button
        size="xl"
        className={`w-full transition-all duration-300 ${isValid ? "opacity-100 translate-y-0" : "opacity-50 translate-y-1"}`}
        disabled={!isValid}
        onClick={handleContinue}
      >
        {isValid ? `Pledge £${(activeAmount / 100).toFixed(activeAmount % 100 === 0 ? 0 : 2)} →` : "Choose an amount"}
      </Button>

      <p className="text-center text-xs text-muted-foreground">
        No payment now — choose how to pay on the next step
      </p>
    </div>
  )
}