import { useMemo, useState } from "react";
import { useParams } from "react-router-dom";
import { useCourseDetail, useTrackProgress } from "@/hooks/queries/useCourseGeneration";
import type { ModuleConfig, ModuleResource } from "@/types";
import { Button } from "@/components/ui/button";
import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/components/ui/card";
import { Badge } from "@/components/ui/badge";
import { Progress } from "@/components/ui/progress";
import { Collapsible, CollapsibleContent, CollapsibleTrigger } from "@/components/ui/collapsible";
import { Separator } from "@/components/ui/separator";
import { Skeleton } from "@/components/ui/skeleton";
import { ScrollArea } from "@/components/ui/scroll-area";
import {
  BookOpen,
  Check,
  ChevronDown,
  FileText,
  Headphones,
  Lock,
  Sparkles,
  Video,
} from "lucide-react";
import { cn } from "@/lib/utils";

function ResourceIcon({ type }: { type: ModuleResource["type"] }) {
  switch (type) {
    case "pdf":
      return <FileText className="h-4 w-4" />;
    case "video":
      return <Video className="h-4 w-4" />;
    case "audio":
      return <Headphones className="h-4 w-4" />;
    default:
      return <BookOpen className="h-4 w-4" />;
  }
}

export default function CourseDelivery() {
  const { courseId: courseIdParam } = useParams();
  const courseId = Number(courseIdParam);
  const { data: course, isLoading } = useCourseDetail(courseId);
  const track = useTrackProgress();

  const [activeResource, setActiveResource] = useState<{ module: ModuleConfig; resource: ModuleResource } | null>(null);

  const bySkill = useMemo(() => {
    const map = new Map<string, ModuleConfig[]>();
    course?.modules.forEach((m) => {
      const k = m.skill || "General";
      if (!map.has(k)) map.set(k, []);
      map.get(k)!.push(m);
    });
    return map;
  }, [course]);

  const overallProgress = useMemo(() => {
    if (!course?.modules.length) return 0;
    const sum = course.modules.reduce((s, m) => s + (m.progress_percent ?? 0), 0);
    return Math.round(sum / course.modules.length);
  }, [course]);

  const weeksLeft = course ? Math.max(0, course.duration_weeks - 2) : 0;

  const markResource = (mod: ModuleConfig, res: ModuleResource) => {
    track.mutate({
      courseId,
      progress: {
        resource_id: res.id,
        completion_percent: 100,
        time_spent_ms: 60000,
      },
    });
    setActiveResource({ module: mod, resource: res });
  };

  if (isLoading) {
    return (
      <div className="p-6">
        <Skeleton className="mb-4 h-12 w-full" />
        <Skeleton className="h-96 w-full" />
      </div>
    );
  }

  return (
    <div className="mx-auto max-w-5xl space-y-8 p-6">
      <Card>
        <CardHeader>
          <div className="flex flex-wrap items-start justify-between gap-4">
            <div>
              <CardTitle className="text-2xl">{course?.title ?? `Course #${courseId}`}</CardTitle>
              <CardDescription>
                {course?.exam_type ?? "IELTS"} · Target {course?.target_band ?? course?.target_level ?? "—"}
              </CardDescription>
            </div>
            <Badge variant="secondary">{course?.progression_model ?? "linear"}</Badge>
          </div>
          <div className="mt-4 space-y-2">
            <div className="flex justify-between text-sm">
              <span>Overall progress</span>
              <span>{overallProgress}%</span>
            </div>
            <Progress value={overallProgress} />
            <p className="text-sm text-muted-foreground">About {weeksLeft} weeks remaining at your current pace</p>
          </div>
        </CardHeader>
      </Card>

      <div className="grid gap-6 lg:grid-cols-2">
        <div className="space-y-4">
          {Array.from(bySkill.entries()).map(([skill, mods]) => (
            <Collapsible key={skill} defaultOpen>
              <Card>
                <CollapsibleTrigger asChild>
                  <CardHeader className="flex cursor-pointer flex-row items-center justify-between py-3">
                    <CardTitle className="text-base">{skill}</CardTitle>
                    <ChevronDown className="h-5 w-5" />
                  </CardHeader>
                </CollapsibleTrigger>
                <CollapsibleContent>
                  <CardContent className="space-y-4 pt-0">
                    {mods.map((mod) => (
                      <div key={mod.id} className="rounded-lg border p-4">
                        <div className="mb-2 flex flex-wrap items-center gap-2">
                          <h3 className="font-semibold">{mod.title}</h3>
                          {mod.status === "locked" ? <Lock className="h-4 w-4 text-muted-foreground" /> : null}
                          {mod.id === course?.modules.find((m) => m.status === "in_progress")?.id ? (
                            <Badge>Recommended Next</Badge>
                          ) : null}
                          {mod.status === "skipped" ? <Badge variant="outline">Skipped</Badge> : null}
                        </div>
                        <div className="mb-2 text-xs text-muted-foreground">
                          {mod.estimated_hours}h · {mod.cefr_target ?? "CEFR target"}
                        </div>
                        <Progress value={mod.progress_percent ?? 0} className="mb-3 h-2" />
                        <div className="space-y-2">
                          {mod.resources.map((r) => (
                            <button
                              key={r.id}
                              type="button"
                              onClick={() => markResource(mod, r)}
                              className="flex w-full items-center justify-between rounded-md border bg-background px-3 py-2 text-left text-sm hover:bg-muted/50"
                            >
                              <span className="flex items-center gap-2">
                                <ResourceIcon type={r.type} />
                                {r.title}
                              </span>
                              {r.completed ? <Check className="h-4 w-4 text-green-600" /> : null}
                            </button>
                          ))}
                        </div>
                        <div className="mt-3 flex gap-2">
                          <Button type="button" size="sm" disabled={mod.status === "locked"}>
                            {mod.status === "in_progress" || mod.progress_percent ? "Continue" : "Start"}
                          </Button>
                        </div>
                      </div>
                    ))}
                  </CardContent>
                </CollapsibleContent>
              </Card>
            </Collapsible>
          ))}
        </div>

        <Card className="min-h-[320px]">
          <CardHeader>
            <CardTitle className="text-base">Resource viewer</CardTitle>
            <CardDescription>
              {activeResource ? activeResource.resource.title : "Select a resource to open the viewer"}
            </CardDescription>
          </CardHeader>
          <CardContent>
            {!activeResource ? (
              <p className="text-sm text-muted-foreground">PDF, video, audio, and exercise viewers render here.</p>
            ) : (
              <div className="space-y-3">
                <div
                  className={cn(
                    "flex min-h-[200px] items-center justify-center rounded-lg border bg-muted/30 p-6 text-center text-sm text-muted-foreground",
                  )}
                >
                  {activeResource.resource.type === "pdf" && "PDF viewer placeholder"}
                  {activeResource.resource.type === "video" && "Video player placeholder"}
                  {activeResource.resource.type === "audio" && "Audio player placeholder"}
                  {activeResource.resource.type === "exercise" && "Interactive exercise placeholder"}
                  {activeResource.resource.type === "ai_generated" && (
                    <span className="flex items-center gap-2">
                      <Sparkles className="h-4 w-4" /> AI-generated content placeholder
                    </span>
                  )}
                </div>
                <Separator />
                <ScrollArea className="h-32 text-xs text-muted-foreground">
                  Module: {activeResource.module.title}. Completion: {activeResource.module.completion_criteria}.
                </ScrollArea>
              </div>
            )}
          </CardContent>
        </Card>
      </div>
    </div>
  );
}