"use client";

import { useEffect, useMemo, useState } from "react";
import Link from "next/link";
import {
  AlertCircle,
  Calendar,
  CalendarRange,
  CheckCircle2,
  ChevronLeft,
  ChevronRight,
  Filter,
  GanttChartSquare,
  Layers,
  PanelLeftClose,
  PanelLeftOpen,
  Search,
} from "lucide-react";

import { Badge } from "@/components/ui/badge";
import { Button } from "@/components/ui/button";
import { Card, CardContent } from "@/components/ui/card";
import { Checkbox } from "@/components/ui/checkbox";
import { Input } from "@/components/ui/input";
import {
  Select,
  SelectContent,
  SelectItem,
  SelectTrigger,
  SelectValue,
} from "@/components/ui/select";
import { Skeleton } from "@/components/ui/skeleton";
import { getProjects } from "@/lib/projectsService";
import { Project, ProjectStatus } from "@/types/project";

const MONTH_WIDTH_PX = 72;
const ROW_HEIGHT_PX = 52;

type ProjectStatusFilter = "all" | ProjectStatus;
type ZoomLevel = "compact" | "normal" | "detailed";

const STATUS_LABELS: Record<ProjectStatus, string> = {
  "0": "Borrador",
  "1": "Abierto",
  "2": "Cerrado",
};

const STATUS_BADGE_CLASS: Record<ProjectStatus, string> = {
  "0": "bg-gray-100 text-gray-700 border-gray-200 dark:bg-gray-800 dark:text-gray-300 dark:border-gray-700",
  "1": "bg-blue-100 text-blue-700 border-blue-200 dark:bg-blue-900/35 dark:text-blue-300 dark:border-blue-800",
  "2": "bg-green-100 text-green-700 border-green-200 dark:bg-green-900/35 dark:text-green-300 dark:border-green-800",
};

const BAR_COLOR_BY_STATUS: Record<ProjectStatus, { base: string; fill: string }> = {
  "0": { base: "bg-gray-200 dark:bg-gray-700", fill: "bg-gray-500 dark:bg-gray-400" },
  "1": { base: "bg-blue-100 dark:bg-blue-950/50", fill: "bg-gradient-to-r from-blue-500 to-violet-600" },
  "2": { base: "bg-green-100 dark:bg-green-950/50", fill: "bg-gradient-to-r from-emerald-500 to-green-600" },
};

interface TimelineMonth {
  month: number;
  year: number;
  label: string;
}

interface PlannedProject {
  project: Project;
  start: Date;
  end: Date;
  startOffsetDays: number;
  durationDays: number;
}

function getMonthsBetween(start: Date, end: Date): TimelineMonth[] {
  const months: TimelineMonth[] = [];
  const current = new Date(start.getFullYear(), start.getMonth(), 1);
  const endMonth = new Date(end.getFullYear(), end.getMonth(), 1);

  while (current <= endMonth) {
    months.push({
      month: current.getMonth(),
      year: current.getFullYear(),
      label: current.toLocaleDateString("es-ES", { month: "short", year: "numeric" }),
    });
    current.setMonth(current.getMonth() + 1);
  }

  return months;
}

function getDaysBetween(start: Date, end: Date): number {
  const msPerDay = 1000 * 60 * 60 * 24;
  const startMidnight = new Date(start.getFullYear(), start.getMonth(), start.getDate());
  const endMidnight = new Date(end.getFullYear(), end.getMonth(), end.getDate());
  return Math.floor((endMidnight.getTime() - startMidnight.getTime()) / msPerDay);
}

function clamp(value: number, min: number, max: number): number {
  return Math.min(max, Math.max(min, value));
}

function parseProjectDates(project: Project): { start: Date; end: Date } | null {
  const start = new Date(project.startDate);
  const end = new Date(project.endDate);
  if (isNaN(start.getTime()) || isNaN(end.getTime())) return null;

  if (start <= end) return { start, end };
  return { start: end, end: start };
}

function formatDate(date: Date): string {
  return date.toLocaleDateString("es-ES", {
    day: "2-digit",
    month: "short",
    year: "numeric",
  });
}

export default function GanttPage() {
  const [projects, setProjects] = useState<Project[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);

  const [statusFilter, setStatusFilter] = useState<ProjectStatusFilter>("all");
  const [search, setSearch] = useState("");
  const [zoom, setZoom] = useState<ZoomLevel>("normal");
  const [selectedIds, setSelectedIds] = useState<number[]>([]);
  const [showSelectionPanel, setShowSelectionPanel] = useState(true);

  useEffect(() => {
    async function load() {
      try {
        setLoading(true);
        const data = await getProjects();
        const sorted = [...data].sort((a, b) => {
          const da = parseProjectDates(a)?.start.getTime() ?? Number.MAX_SAFE_INTEGER;
          const db = parseProjectDates(b)?.start.getTime() ?? Number.MAX_SAFE_INTEGER;
          return da - db;
        });
        setProjects(sorted);
        setSelectedIds(sorted.map((project) => project.id));
        setError(null);
      } catch (err) {
        console.error("Error loading projects:", err);
        setError("No se pudieron cargar los proyectos para el Gantt");
      } finally {
        setLoading(false);
      }
    }

    load();
  }, []);

  const filteredProjects = useMemo(() => {
    return projects.filter((project) => {
      const statusOk = statusFilter === "all" || project.status === statusFilter;
      const searchValue = search.trim().toLowerCase();
      const searchOk =
        searchValue.length === 0 ||
        project.name.toLowerCase().includes(searchValue) ||
        project.client.toLowerCase().includes(searchValue) ||
        project.ref.toLowerCase().includes(searchValue);

      return statusOk && searchOk;
    });
  }, [projects, search, statusFilter]);

  useEffect(() => {
    setSelectedIds((current) => {
      const available = new Set(filteredProjects.map((project) => project.id));
      const kept = current.filter((id) => available.has(id));
      if (kept.length === current.length) return current;
      return kept;
    });
  }, [filteredProjects]);

  const visibleProjects = useMemo(() => {
    const selected = new Set(selectedIds);
    return filteredProjects.filter((project) => selected.has(project.id));
  }, [filteredProjects, selectedIds]);

  const { timelineStart, timelineEnd, months, totalDays } = useMemo(() => {
    const projectsWithDates = visibleProjects
      .map((project) => ({ project, parsed: parseProjectDates(project) }))
      .filter((item): item is { project: Project; parsed: { start: Date; end: Date } } => item.parsed !== null);

    if (projectsWithDates.length === 0) {
      const now = new Date();
      const start = new Date(now.getFullYear(), now.getMonth() - 2, 1);
      const end = new Date(now.getFullYear(), now.getMonth() + 3, 0);
      const monthList = getMonthsBetween(start, end);
      return {
        timelineStart: start,
        timelineEnd: end,
        months: monthList,
        totalDays: Math.max(1, getDaysBetween(start, end) + 1),
      };
    }

    const minStart = new Date(
      Math.min(...projectsWithDates.map((item) => item.parsed.start.getTime()))
    );
    const maxEnd = new Date(
      Math.max(...projectsWithDates.map((item) => item.parsed.end.getTime()))
    );

    const start = new Date(minStart.getFullYear(), minStart.getMonth(), 1);
    const end = new Date(maxEnd.getFullYear(), maxEnd.getMonth() + 1, 0);
    const monthList = getMonthsBetween(start, end);

    return {
      timelineStart: start,
      timelineEnd: end,
      months: monthList,
      totalDays: Math.max(1, getDaysBetween(start, end) + 1),
    };
  }, [visibleProjects]);

  const todayPercent = useMemo(() => {
    const now = new Date();
    if (now < timelineStart || now > timelineEnd) return null;
    const offset = getDaysBetween(timelineStart, now);
    return clamp((offset / totalDays) * 100, 0, 100);
  }, [timelineEnd, timelineStart, totalDays]);

  const plannedRows = useMemo<PlannedProject[]>(() => {
    return visibleProjects
      .map((project) => {
        const parsed = parseProjectDates(project);
        if (!parsed) return null;

        const startOffsetDays = clamp(getDaysBetween(timelineStart, parsed.start), 0, totalDays - 1);
        const durationDays = Math.max(1, getDaysBetween(parsed.start, parsed.end) + 1);

        return {
          project,
          start: parsed.start,
          end: parsed.end,
          startOffsetDays,
          durationDays,
        };
      })
      .filter((item): item is PlannedProject => item !== null);
  }, [timelineStart, totalDays, visibleProjects]);

  const timelineWidth = months.length * MONTH_WIDTH_PX;

  const stats = useMemo(() => {
    const total = visibleProjects.length;
    const open = visibleProjects.filter((project) => project.status === "1").length;
    const closed = visibleProjects.filter((project) => project.status === "2").length;
    const draft = visibleProjects.filter((project) => project.status === "0").length;
    return { total, open, closed, draft };
  }, [visibleProjects]);

  const selectAll = () => setSelectedIds(filteredProjects.map((project) => project.id));
  const clearSelection = () => setSelectedIds([]);

  const toggleProjectSelection = (projectId: number, checked: boolean) => {
    setSelectedIds((current) => {
      if (checked && current.includes(projectId)) return current;
      if (!checked && !current.includes(projectId)) return current;
      return checked ? [...current, projectId] : current.filter((id) => id !== projectId);
    });
  };

  if (error) {
    return (
      <div className="min-h-screen bg-background flex items-center justify-center px-4">
        <div className="text-center max-w-md">
          <AlertCircle className="w-12 h-12 text-red-500 mx-auto mb-3" />
          <h2 className="text-lg font-semibold text-foreground">Error cargando el Gantt</h2>
          <p className="text-sm text-muted-foreground mt-1">{error}</p>
          <Button onClick={() => window.location.reload()} className="mt-4">Reintentar</Button>
        </div>
      </div>
    );
  }

  return (
    <div className="min-h-screen bg-background">
      <section className="border-b header-gradient">
        <div className="px-4 sm:px-6 lg:px-8 py-5 space-y-4">
          <div className="flex items-start justify-between gap-4 flex-wrap">
            <div className="flex items-center gap-3">
              <div className="p-2 rounded-lg bg-gradient-to-r from-blue-500 to-violet-600 shadow-sm">
                <GanttChartSquare className="w-5 h-5 text-white" />
              </div>
              <div>
                <h1 className="text-2xl font-bold text-foreground">Roadmap de Proyectos</h1>
                <p className="text-sm text-muted-foreground">Vista global rediseñada para planificación ejecutiva</p>
              </div>
            </div>

            <div className="flex items-center gap-2 flex-wrap">
              <Button
                variant="outline"
                onClick={() => setShowSelectionPanel((current) => !current)}
                className="gap-2"
                aria-label={showSelectionPanel ? "Ocultar selección de proyectos" : "Mostrar selección de proyectos"}
              >
                {showSelectionPanel ? <PanelLeftClose className="w-4 h-4" /> : <PanelLeftOpen className="w-4 h-4" />}
                {showSelectionPanel ? "Ocultar selección" : "Mostrar selección"}
              </Button>

              <div className="relative">
                <Search className="w-4 h-4 text-muted-foreground absolute left-2.5 top-2.5" />
                <Input
                  value={search}
                  onChange={(event) => setSearch(event.target.value)}
                  placeholder="Buscar proyecto..."
                  className="pl-8 w-56"
                />
              </div>

              <Select value={statusFilter} onValueChange={(value: ProjectStatusFilter) => setStatusFilter(value)}>
                <SelectTrigger className="w-40">
                  <Filter className="w-4 h-4 mr-2" />
                  <SelectValue placeholder="Estado" />
                </SelectTrigger>
                <SelectContent>
                  <SelectItem value="all">Todos</SelectItem>
                  <SelectItem value="0">Borrador</SelectItem>
                  <SelectItem value="1">Abierto</SelectItem>
                  <SelectItem value="2">Cerrado</SelectItem>
                </SelectContent>
              </Select>

              <Select value={zoom} onValueChange={(value: ZoomLevel) => setZoom(value)}>
                <SelectTrigger className="w-36">
                  <CalendarRange className="w-4 h-4 mr-2" />
                  <SelectValue placeholder="Zoom" />
                </SelectTrigger>
                <SelectContent>
                  <SelectItem value="compact">Compacto</SelectItem>
                  <SelectItem value="normal">Normal</SelectItem>
                  <SelectItem value="detailed">Detallado</SelectItem>
                </SelectContent>
              </Select>
            </div>
          </div>

          <div className="flex items-center gap-2 flex-wrap">
            <Badge variant="outline" className="bg-background/80">{stats.total} visibles</Badge>
            <Badge variant="outline" className="bg-background/80">{stats.open} abiertos</Badge>
            <Badge variant="outline" className="bg-background/80">{stats.closed} cerrados</Badge>
            <Badge variant="outline" className="bg-background/80">{stats.draft} borradores</Badge>
          </div>
        </div>
      </section>

      <main className="px-4 sm:px-6 lg:px-8 py-6">
        {loading ? (
          <GanttSkeleton />
        ) : (
          <div className={`grid grid-cols-1 gap-4 ${showSelectionPanel ? "xl:grid-cols-[320px_1fr]" : "xl:grid-cols-1"}`}>
            {showSelectionPanel && (
              <Card className="border shadow-sm">
                <CardContent className="p-4 space-y-3">
                  <div className="flex items-center justify-between">
                    <h2 className="text-sm font-semibold text-foreground flex items-center gap-2">
                      <Layers className="w-4 h-4" />
                      Selección de proyectos
                    </h2>
                    <span className="text-xs text-muted-foreground">{selectedIds.length}/{filteredProjects.length}</span>
                  </div>

                  <div className="flex items-center gap-2">
                    <Button variant="outline" size="sm" onClick={selectAll}>Seleccionar todos</Button>
                    <Button variant="ghost" size="sm" onClick={clearSelection}>Limpiar</Button>
                  </div>

                  <div className="max-h-[60vh] overflow-auto border rounded-md">
                    {filteredProjects.length === 0 ? (
                      <div className="p-4 text-sm text-muted-foreground">No hay proyectos con este filtro.</div>
                    ) : (
                      filteredProjects.map((project) => {
                        const checked = selectedIds.includes(project.id);
                        return (
                          <label
                            key={project.id}
                            className="flex items-start gap-2.5 p-2.5 border-b last:border-b-0 hover:bg-muted/50 cursor-pointer"
                          >
                            <Checkbox
                              checked={checked}
                              onCheckedChange={(value) => toggleProjectSelection(project.id, Boolean(value))}
                              className="mt-0.5"
                            />
                            <div className="min-w-0 flex-1">
                              <p className="text-sm font-medium text-foreground truncate">{project.name}</p>
                              <div className="mt-1 flex items-center gap-2">
                                <Badge variant="outline" className={`text-[10px] px-1.5 py-0 h-5 ${STATUS_BADGE_CLASS[project.status]}`}>
                                  {STATUS_LABELS[project.status]}
                                </Badge>
                                <span className="text-[11px] text-muted-foreground truncate">{project.client}</span>
                              </div>
                            </div>
                          </label>
                        );
                      })
                    )}
                  </div>
                </CardContent>
              </Card>
            )}


            <Card className="border shadow-sm overflow-hidden">
              <CardContent className="p-0">
                {plannedRows.length === 0 ? (
                  <div className="py-14 px-6 text-center">
                    <Calendar className="w-10 h-10 text-muted-foreground/60 mx-auto mb-3" />
                    <p className="font-medium text-foreground">No hay proyectos seleccionados para mostrar</p>
                    <p className="text-sm text-muted-foreground mt-1">
                      Selecciona proyectos en el panel izquierdo para ver el cronograma.
                    </p>
                  </div>
                ) : (
                  <div className="overflow-auto">
                    <div style={{ width: `${Math.max(980, timelineWidth + 320)}px` }}>
                      <div className="grid grid-cols-[320px_1fr] border-b sticky top-0 z-10 bg-card/95 backdrop-blur">
                        <div className="h-12 flex items-center px-4 text-xs font-semibold text-muted-foreground border-r sticky left-0 z-20 bg-card/95">
                          Proyecto
                        </div>
                        <div className="h-12 flex">
                          {months.map((month) => (
                            <div
                              key={`${month.year}-${month.month}`}
                              className="border-r flex items-center justify-center"
                              style={{ width: `${MONTH_WIDTH_PX}px` }}
                            >
                              <span className="text-[11px] font-medium text-muted-foreground uppercase">{month.label}</span>
                            </div>
                          ))}
                        </div>
                      </div>

                      {plannedRows.map((row) => {
                        const barStyle = BAR_COLOR_BY_STATUS[row.project.status];
                        const leftPercent = (row.startOffsetDays / totalDays) * 100;
                        const widthPercent = (row.durationDays / totalDays) * 100;
                        const isCompleted = row.project.progress >= 100;

                        return (
                          <div key={row.project.id} className="grid grid-cols-[320px_1fr] border-b" style={{ minHeight: `${ROW_HEIGHT_PX}px` }}>
                            <Link
                              href={`/proyectos/${row.project.id}`}
                              className="px-4 py-2.5 border-r hover:bg-muted/50 transition-colors flex items-center sticky left-0 z-10 bg-background"
                            >
                              <div className="min-w-0">
                                <p className="text-sm font-medium text-foreground truncate">{row.project.name}</p>
                                <div className="mt-1 flex items-center gap-2">
                                  <Badge variant="outline" className={`text-[10px] px-1.5 py-0 h-5 ${STATUS_BADGE_CLASS[row.project.status]}`}>
                                    {STATUS_LABELS[row.project.status]}
                                  </Badge>
                                  <span className="text-[11px] text-muted-foreground">{row.project.progress}%</span>
                                  {isCompleted && <CheckCircle2 className="w-3.5 h-3.5 text-green-500" />}
                                </div>
                              </div>
                            </Link>

                            <div className="relative">
                              <div className="absolute inset-0 flex pointer-events-none">
                                {months.map((month) => (
                                  <div key={`grid-${row.project.id}-${month.year}-${month.month}`} className="border-r" style={{ width: `${MONTH_WIDTH_PX}px` }} />
                                ))}
                              </div>

                              {todayPercent !== null && (
                                <div
                                  className="absolute top-0 bottom-0 w-px bg-red-400/70 z-[1]"
                                  style={{ left: `${todayPercent}%` }}
                                />
                              )}

                              <Link
                                href={`/proyectos/${row.project.id}`}
                                className="absolute top-1/2 -translate-y-1/2 h-8 rounded-md transition-all hover:scale-[1.01] hover:shadow-sm focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-blue-500"
                                style={{
                                  left: `${leftPercent}%`,
                                  width: `${Math.max(widthPercent, 1.2)}%`,
                                  minWidth: zoom === "compact" ? "18px" : zoom === "normal" ? "22px" : "26px",
                                }}
                              >
                                <div className={`absolute inset-0 rounded-md ${barStyle.base}`} />
                                <div
                                  className={`absolute inset-y-0 left-0 rounded-md ${barStyle.fill}`}
                                  style={{ width: `${clamp(row.project.progress, 0, 100)}%` }}
                                />
                                <div className="relative h-full px-2 flex items-center justify-between z-10">
                                  {zoom !== "compact" && (
                                    <span className="text-[11px] font-semibold text-white drop-shadow truncate">
                                      {zoom === "detailed" ? `${row.project.progress}%` : row.project.progress >= 35 ? `${row.project.progress}%` : ""}
                                    </span>
                                  )}
                                  {zoom === "detailed" && (
                                    <span className="text-[10px] text-white/95 hidden md:inline-flex items-center gap-1">
                                      <ChevronLeft className="w-3 h-3 rotate-180" />
                                      {formatDate(row.start)}
                                      <ChevronRight className="w-3 h-3" />
                                      {formatDate(row.end)}
                                    </span>
                                  )}
                                </div>
                              </Link>
                            </div>
                          </div>
                        );
                      })}
                    </div>
                  </div>
                )}
              </CardContent>
            </Card>
          </div>
        )}
      </main>
    </div>
  );
}

function GanttSkeleton() {
  return (
    <div className="grid grid-cols-1 xl:grid-cols-[320px_1fr] gap-4">
      <Card className="border">
        <CardContent className="p-4 space-y-3">
          <Skeleton className="h-5 w-40" />
          <div className="space-y-2">
            {Array.from({ length: 7 }).map((_, index) => (
              <Skeleton key={index} className="h-14 w-full" />
            ))}
          </div>
        </CardContent>
      </Card>
      <Card className="border">
        <CardContent className="p-0">
          <div className="space-y-0">
            <Skeleton className="h-12 w-full rounded-none" />
            {Array.from({ length: 8 }).map((_, index) => (
              <Skeleton key={index} className="h-[52px] w-full rounded-none border-t" />
            ))}
          </div>
        </CardContent>
      </Card>
    </div>
  );
}