import { useState, useEffect } from 'react';
import { useParams, useNavigate } from 'react-router-dom';
import { useAuthStore } from '../stores/authStore.ts';
import api from '../services/api.ts';
import { Pencil, Trash2, ArrowLeft, Calendar, Euro, FileText, Layers, FolderOpen, ListChecks, Plus } from 'lucide-react';
import FunctionGroupEditor from '../components/FunctionGroupEditor.tsx';

interface ProjectDetailData {
  id: string;
  account_id: string;
  name: string;
  description: string | null;
  status: string;
  start_date: string | null;
  end_date: string | null;
  budget: number | null;
  total_costs: number;
  notes: string | null;
  created_at: string;
  updated_at: string;
}

interface SubProjectItem {
  id: string;
  name: string;
  project_id: string;
  parent_id: string | null;
  sort_order: number;
}

interface FunctionGroupItem {
  id: string;
  name: string;
  project_id: string;
  sort_order: number;
}

interface FunctionItem {
  id: string;
  name: string;
  function_group_id: string;
  quantity: number;
  daily_costs: number;
  total_costs: number;
  sort_order: number;
}

export default function ProjectDetail() {
  const { projectId } = useParams<{ projectId: string }>();
  const { user } = useAuthStore();
  const navigate = useNavigate();

  const [project, setProject] = useState<ProjectDetailData | null>(null);
  const [subProjects, setSubProjects] = useState<SubProjectItem[]>([]);
  const [functionGroups, setFunctionGroups] = useState<FunctionGroupItem[]>([]);
  const [functionsMap, setFunctionsMap] = useState<Record<string, FunctionItem[]>>({});
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);

  const canWrite = user?.permissions?.includes('projects:write');
  const canDelete = user?.permissions?.includes('projects:delete');

  useEffect(() => {
    loadAll();
  }, [projectId]);

  const loadAll = async () => {
    try {
      setLoading(true);

      // Load project details
      const projectRes = await api.get(`/projects/${projectId}`);
      setProject(projectRes.data);

      // Load subprojects
      const subRes = await api.get(`/projects/${projectId}/subprojects?size=100`);
      setSubProjects(subRes.data.items || []);

      // Load function groups
      const fgRes = await api.get(`/projects/${projectId}/function-groups?size=100`);
      const fgs: FunctionGroupItem[] = fgRes.data.items || [];
      setFunctionGroups(fgs);

      // Load functions for each function group
      const funcMap: Record<string, FunctionItem[]> = {};
      await Promise.all(
        fgs.map(async (fg) => {
          try {
            const funcRes = await api.get(`/projects/${projectId}/function-groups/${fg.id}/functions?size=100`);
            funcMap[fg.id] = funcRes.data.items || [];
          } catch {
            funcMap[fg.id] = [];
          }
        })
      );
      setFunctionsMap(funcMap);
    } catch (err: any) {
      setError(err.response?.data?.detail || 'Failed to load project');
    } finally {
      setLoading(false);
    }
  };

  const handleDelete = async () => {
    if (!confirm(`Delete project "${project?.name}"?`)) return;
    try {
      await api.delete(`/projects/${projectId}`);
      navigate('/projects');
    } catch (err: any) {
      alert(err.response?.data?.detail || 'Failed to delete project');
    }
  };

  const getStatusBadge = (status: string) => {
    const styles: Record<string, string> = {
      draft: 'bg-gray-100 text-gray-800',
      confirmed: 'bg-blue-100 text-blue-800',
      in_progress: 'bg-yellow-100 text-yellow-800',
      completed: 'bg-green-100 text-green-800',
      cancelled: 'bg-red-100 text-red-800',
    };
    return styles[status] || 'bg-gray-100 text-gray-800';
  };

  const formatDate = (dateStr: string | null) => {
    if (!dateStr) return '-';
    const d = new Date(dateStr);
    return d.toLocaleDateString('de-DE', { day: '2-digit', month: '2-digit', year: 'numeric' });
  };

  const iconClass = "w-5 h-5 text-text-secondary mt-0.5 flex-shrink-0";
  const labelClass = "text-sm text-text-secondary min-w-[120px]";
  const valueClass = "text-sm text-text-primary";
  const fieldRowClass = "flex items-start gap-3 py-2";
  const sectionClass = "mb-8";
  const headingClass = "text-lg font-semibold text-text-primary mb-3";

  if (loading) return <div className="p-6"><p className="text-text-secondary">Loading project...</p></div>;
  if (error) return <div className="p-6"><p className="text-red-500">{error}</p></div>;
  if (!project) return <div className="p-6"><p className="text-text-secondary">Project not found.</p></div>;

  return (
    <div className="p-6 max-w-5xl mx-auto">
      {/* Header */}
      <div className="flex items-center justify-between mb-6">
        <button
          onClick={() => navigate('/projects')}
          className="flex items-center gap-2 text-text-secondary hover:text-text-primary transition-colors"
        >
          <ArrowLeft size={20} />
          <span className="text-sm">Back to Projects</span>
        </button>
        <div className="flex items-center gap-2">
          {canWrite && (
            <button
              onClick={() => navigate(`/projects/${project.id}/edit`)}
              className="flex items-center gap-2 px-4 py-2 bg-primary text-white rounded-lg hover:bg-primary-dark transition-colors text-sm"
            >
              <Pencil size={16} />
              Edit
            </button>
          )}
          {canDelete && (
            <button
              onClick={handleDelete}
              className="flex items-center gap-2 px-4 py-2 bg-red-600 text-white rounded-lg hover:bg-red-700 transition-colors text-sm"
            >
              <Trash2 size={16} />
              Delete
            </button>
          )}
        </div>
      </div>

      {/* Title */}
      <div className="mb-6">
        <h1 className="text-2xl font-bold text-text-primary">{project.name}</h1>
        <div className="flex items-center gap-3 mt-2">
          <span className={`inline-block px-3 py-1 rounded-full text-xs font-medium ${getStatusBadge(project.status)}`}>
            {project.status.replace(/_/g, ' ').replace(/\b\w/g, c => c.toUpperCase())}
          </span>
        </div>
      </div>

      {/* Project Details */}
      <div className={sectionClass}>
        <h2 className={headingClass}><FileText className="inline w-5 h-5 mr-2" />Project Details</h2>
        <div className="bg-surface rounded-lg border border-border p-4 space-y-1">
          {project.description && (
            <div className={fieldRowClass}>
              <FileText className={iconClass} />
              <span className={labelClass}>Description</span>
              <span className={valueClass}>{project.description}</span>
            </div>
          )}
          <div className={fieldRowClass}>
            <Calendar className={iconClass} />
            <span className={labelClass}>Start Date</span>
            <span className={valueClass}>{formatDate(project.start_date)}</span>
          </div>
          <div className={fieldRowClass}>
            <Calendar className={iconClass} />
            <span className={labelClass}>End Date</span>
            <span className={valueClass}>{formatDate(project.end_date)}</span>
          </div>
          <div className={fieldRowClass}>
            <Euro className={iconClass} />
            <span className={labelClass}>Budget</span>
            <span className={valueClass}>{project.budget != null ? `€${project.budget.toFixed(2)}` : '-'}</span>
          </div>
          <div className={fieldRowClass}>
            <Euro className={iconClass} />
            <span className={labelClass}>Total Costs</span>
            <span className={valueClass}>{project.total_costs != null ? `€${project.total_costs.toFixed(2)}` : '-'}</span>
          </div>
          {project.notes && (
            <div className={fieldRowClass}>
              <FileText className={iconClass} />
              <span className={labelClass}>Notes</span>
              <span className={valueClass}>{project.notes}</span>
            </div>
          )}
        </div>
      </div>

      {/* SubProjects Section */}
      <div className={sectionClass}>
        <div className="flex items-center justify-between mb-3">
          <h2 className={headingClass}><Layers className="inline w-5 h-5 mr-2" />Sub-Projects ({subProjects.length})</h2>
        </div>
        {subProjects.length === 0 ? (
          <p className="text-text-secondary text-sm">No sub-projects defined yet.</p>
        ) : (
          <div className="space-y-2">
            {subProjects.map(sp => (
              <div key={sp.id} className="bg-surface rounded-lg border border-border p-3 flex items-center justify-between">
                <div className="flex items-center gap-3">
                  <Layers size={18} className="text-text-secondary flex-shrink-0" />
                  <div>
                    <p className="text-sm font-medium text-text-primary">{sp.name}</p>
                    <p className="text-xs text-text-secondary">Sort order: {sp.sort_order}</p>
                  </div>
                </div>
                {sp.parent_id && (
                  <span className="text-xs text-text-secondary bg-gray-100 px-2 py-1 rounded">Child</span>
                )}
              </div>
            ))}
          </div>
        )}
      </div>

      {/* Function Groups Section - Inline Editor */}
      <div className={sectionClass}>
        <div className="flex items-center justify-between mb-3">
          <h2 className={headingClass}><FolderOpen className="inline w-5 h-5 mr-2" />Function Groups ({functionGroups.length})</h2>
        </div>
        <FunctionGroupEditor
          projectId={project.id}
          functionGroups={functionGroups}
          functionsMap={functionsMap}
          onReload={loadAll}
          canWrite={canWrite}
          canDelete={canDelete}
        />
      </div>
    </div>
  );
}