import React, { useState } from 'react';
import { UserAvatar } from '../ui/UserAvatar';
import { STAGE_COLORS, StageBadge, formatDate, formatDays, relativeDays } from './opportunityUi';
import {
  OPPORTUNITY_STAGES,
  contactFullName,
  formatEuro,
  opportunityVolume,
  type Opportunity,
  type OpportunityStage,
} from '../../types';

interface OpportunityPipelineProps {
  opportunities: Opportunity[];
  onEdit: (opportunity: Opportunity) => void;
  /** Verschiebt eine Karte in eine andere Phase. */
  onStageChange: (opportunity: Opportunity, stage: OpportunityStage) => void;
}

/**
 * Pipeline nach Phasen. Karten lassen sich per Drag & Drop in eine andere Spalte
 * ziehen; wer nicht ziehen mag, nutzt das Auswahlfeld auf der Karte.
 */
export const OpportunityPipeline: React.FC<OpportunityPipelineProps> = ({
  opportunities,
  onEdit,
  onStageChange,
}) => {
  const [draggedId, setDraggedId] = useState<number | null>(null);
  const [hoverStage, setHoverStage] = useState<OpportunityStage | null>(null);

  const byStage = (stage: OpportunityStage) =>
    opportunities.filter((opportunity) => opportunity.stage === stage);

  const columnSum = (stage: OpportunityStage) =>
    byStage(stage).reduce((sum, opportunity) => sum + (opportunityVolume(opportunity) ?? 0), 0);

  const handleDrop = (stage: OpportunityStage) => {
    setHoverStage(null);
    const dragged = opportunities.find((opportunity) => opportunity.id === draggedId);
    setDraggedId(null);
    if (dragged && dragged.stage !== stage) onStageChange(dragged, stage);
  };

  return (
    <div className="scrollbar-slim overflow-x-auto pb-2">
      <div className="flex gap-3" style={{ minWidth: `${OPPORTUNITY_STAGES.length * 250}px` }}>
        {OPPORTUNITY_STAGES.map((stage) => {
          const items = byStage(stage);
          const color = STAGE_COLORS[stage];
          const isTarget = hoverStage === stage;

          return (
            <div
              key={stage}
              data-stage={stage}
              onDragOver={(event) => {
                // Ohne preventDefault laesst der Browser kein Ablegen zu.
                event.preventDefault();
                setHoverStage(stage);
              }}
              onDragLeave={() => setHoverStage((current) => (current === stage ? null : current))}
              onDrop={() => handleDrop(stage)}
              className={`flex w-[250px] shrink-0 flex-col rounded-2xl border transition ${
                isTarget ? 'border-brand-400 bg-brand-50/60' : 'border-ink-200 bg-ink-50/60'
              }`}
            >
              <div className="flex items-center gap-2 border-b border-ink-100 px-3 py-2.5">
                <span className="h-2.5 w-2.5 shrink-0 rounded-full" style={{ backgroundColor: color }} />
                <span className="text-xs font-extrabold uppercase tracking-wider text-ink-600">
                  {stage}
                </span>
                <span className="ml-auto rounded-md bg-ink-100 px-1.5 py-0.5 text-[10px] font-extrabold text-ink-500">
                  {items.length}
                </span>
              </div>

              <div className="border-b border-ink-100 px-3 py-1.5 text-[11px] font-bold text-ink-400">
                {formatEuro(columnSum(stage))}
              </div>

              <div className="scrollbar-slim flex max-h-[62vh] flex-1 flex-col gap-2 overflow-y-auto p-2">
                {items.length === 0 ? (
                  <p className="rounded-xl border border-dashed border-ink-200 px-3 py-6 text-center text-[11px] font-semibold text-ink-300">
                    Karte hierher ziehen
                  </p>
                ) : (
                  items.map((opportunity) => {
                    const interaction = relativeDays(opportunity.last_interaction_at);

                    return (
                      <div
                        key={opportunity.id}
                        draggable
                        onDragStart={() => setDraggedId(opportunity.id)}
                        onDragEnd={() => {
                          setDraggedId(null);
                          setHoverStage(null);
                        }}
                        onClick={() => onEdit(opportunity)}
                        role="button"
                        tabIndex={0}
                        onKeyDown={(event) => {
                          if (event.key === 'Enter' || event.key === ' ') {
                            event.preventDefault();
                            onEdit(opportunity);
                          }
                        }}
                        className={`cursor-grab rounded-xl border border-ink-200 bg-surface p-2.5 shadow-card transition hover:border-brand-300 active:cursor-grabbing ${
                          draggedId === opportunity.id ? 'opacity-40' : ''
                        }`}
                      >
                        <p className="truncate text-xs font-extrabold text-ink-900">
                          {opportunity.title}
                        </p>
                        <p className="truncate text-[11px] text-ink-400">
                          {opportunity.company || 'Ohne Firma'}
                        </p>

                        <div className="mt-2 flex items-center justify-between gap-2">
                          <span className="text-xs font-bold text-ink-800">
                            {formatEuro(opportunityVolume(opportunity))}
                          </span>
                          <span className="text-[11px] font-bold tabular-nums text-ink-400">
                            {opportunity.probability}%
                          </span>
                        </div>

                        <p className="mt-1 text-[11px] text-ink-400">
                          {formatDays(opportunity.duration_days)}
                          {opportunity.start_date && ` ab ${formatDate(opportunity.start_date)}`}
                        </p>

                        {interaction && (
                          <p className="mt-1 text-[11px] text-ink-400">Kontakt {interaction}</p>
                        )}

                        <div className="mt-2 flex items-center gap-2 border-t border-ink-100 pt-2">
                          <span className="min-w-0 flex-1 truncate text-[11px] text-ink-500">
                            {opportunity.contacts.length === 0
                              ? 'kein Ansprechpartner'
                              : opportunity.contacts.length === 1
                                ? contactFullName(opportunity.contacts[0])
                                : `${opportunity.contacts.length} Ansprechpartner`}
                          </span>
                          {opportunity.owner_id !== null && (
                            <UserAvatar
                              user={{
                                id: opportunity.owner_id,
                                name: opportunity.owner_name ?? '?',
                                color: opportunity.owner_color ?? null,
                                avatar: opportunity.owner_avatar ?? null,
                              }}
                              size={20}
                            />
                          )}
                        </div>

                        {/* Tastatur- und Touch-Weg ohne Drag & Drop */}
                        <select
                          value={opportunity.stage}
                          onClick={(event) => event.stopPropagation()}
                          onChange={(event) => {
                            event.stopPropagation();
                            onStageChange(opportunity, event.target.value as OpportunityStage);
                          }}
                          aria-label={`Phase von ${opportunity.title} ändern`}
                          className="mt-2 w-full rounded-lg border border-ink-200 bg-surface px-2 py-1 text-[11px] font-bold text-ink-600 outline-none transition focus:border-brand-500"
                        >
                          {OPPORTUNITY_STAGES.map((option) => (
                            <option key={option} value={option}>
                              {option}
                            </option>
                          ))}
                        </select>
                      </div>
                    );
                  })
                )}
              </div>
            </div>
          );
        })}
      </div>

      {/* Legende der Phasen, damit die Farben auch ausserhalb der Pipeline sitzen */}
      <div className="mt-3 flex flex-wrap gap-2">
        {OPPORTUNITY_STAGES.map((stage) => (
          <StageBadge key={stage} stage={stage} />
        ))}
      </div>
    </div>
  );
};