import { createFileRoute, useSearch } from "@tanstack/react-router";
import { useEffect, useMemo, useState, useCallback } from "react";
import { supabase } from "@/integrations/supabase/client";
import { useAuth } from "@/lib/auth";
import { AppShell, PageContainer, PageHeader } from "@/components/app-shell";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Checkbox } from "@/components/ui/checkbox";
import { Badge } from "@/components/ui/badge";
import { Avatar, AvatarFallback } from "@/components/ui/avatar";
import {
  Select,
  SelectContent,
  SelectItem,
  SelectTrigger,
  SelectValue,
} from "@/components/ui/select";
import { Switch } from "@/components/ui/switch";
import { Label } from "@/components/ui/label";
import { Plus, Search, Calendar as CalIcon, AlertCircle } from "lucide-react";
import { format, isBefore, startOfDay, isSameDay, addDays } from "date-fns";
import { TaskDetailPanel } from "@/components/tasks/task-detail-panel";
import { NewTaskDialog } from "@/components/tasks/new-task-dialog";
import { cn } from "@/lib/utils";

export const Route = createFileRoute("/tasks/")({
  component: TasksPage,
  validateSearch: (search: Record<string, unknown>) => ({
    task: typeof search.task === "string" ? search.task : undefined,
  }),
});

interface TaskRow {
  id: string;
  title: string;
  status: "incomplete" | "complete";
  priority: "low" | "normal" | "high" | "urgent";
  due_date: string | null;
  case_id: string | null;
  parent_task_id: string | null;
  created_by: string | null;
}
interface AssigneeRow {
  task_id: string;
  user_id: string;
}
interface Profile {
  id: string;
  full_name: string;
  email: string;
}
interface CaseRow {
  id: string;
  case_number: string;
  title: string;
}

function initials(name: string) {
  return name.split(" ").map((p) => p[0]).filter(Boolean).slice(0, 2).join("").toUpperCase();
}

const PRIORITY_DOT: Record<string, string> = {
  urgent: "bg-red-500",
  high: "bg-orange-500",
  normal: "bg-blue-500",
  low: "bg-muted-foreground/40",
};

function TasksPage() {
  const { user } = useAuth();
  const search = useSearch({ from: "/tasks/" });
  const [tasks, setTasks] = useState<TaskRow[]>([]);
  const [assignees, setAssignees] = useState<AssigneeRow[]>([]);
  const [profiles, setProfiles] = useState<Profile[]>([]);
  const [cases, setCases] = useState<CaseRow[]>([]);
  const [loading, setLoading] = useState(true);

  const [filterAssignee, setFilterAssignee] = useState<string>("me");
  const [filterStatus, setFilterStatus] = useState<"incomplete" | "complete" | "all">("incomplete");
  const [showOnlyMine, setShowOnlyMine] = useState(false);
  const [query, setQuery] = useState("");

  const [newOpen, setNewOpen] = useState(false);
  const [openTaskId, setOpenTaskId] = useState<string | null>(search.task ?? null);

  const load = useCallback(async () => {
    setLoading(true);
    const [t, a, p, c] = await Promise.all([
      supabase
        .from("tasks")
        .select("id, title, status, priority, due_date, case_id, parent_task_id, created_by")
        .is("parent_task_id", null)
        .order("due_date", { ascending: true, nullsFirst: false }),
      supabase.from("task_assignees").select("task_id, user_id"),
      supabase.from("profiles").select("id, full_name, email"),
      supabase.from("cases").select("id, case_number, title"),
    ]);
    setTasks((t.data ?? []) as TaskRow[]);
    setAssignees((a.data ?? []) as AssigneeRow[]);
    setProfiles((p.data ?? []) as Profile[]);
    setCases((c.data ?? []) as CaseRow[]);
    setLoading(false);
  }, []);

  useEffect(() => {
    load();
    const ch = supabase
      .channel("tasks-list")
      .on("postgres_changes", { event: "*", schema: "public", table: "tasks" }, () => load())
      .on("postgres_changes", { event: "*", schema: "public", table: "task_assignees" }, () => load())
      .subscribe();
    return () => {
      supabase.removeChannel(ch);
    };
  }, [load]);

  useEffect(() => {
    if (search.task) setOpenTaskId(search.task);
  }, [search.task]);

  const profilesById = useMemo(() => Object.fromEntries(profiles.map((p) => [p.id, p])), [profiles]);
  const casesById = useMemo(() => Object.fromEntries(cases.map((c) => [c.id, c])), [cases]);
  const assigneesByTask = useMemo(() => {
    const map: Record<string, string[]> = {};
    for (const a of assignees) {
      (map[a.task_id] = map[a.task_id] || []).push(a.user_id);
    }
    return map;
  }, [assignees]);

  const filtered = useMemo(() => {
    return tasks.filter((t) => {
      if (filterStatus !== "all" && t.status !== filterStatus) return false;
      if (filterAssignee === "me" && user) {
        if (!(assigneesByTask[t.id] || []).includes(user.id)) return false;
      } else if (filterAssignee !== "me" && filterAssignee !== "all") {
        if (!(assigneesByTask[t.id] || []).includes(filterAssignee)) return false;
      }
      if (showOnlyMine && user && t.created_by !== user.id) return false;
      if (query && !t.title.toLowerCase().includes(query.toLowerCase())) return false;
      return true;
    });
  }, [tasks, filterStatus, filterAssignee, showOnlyMine, query, user, assigneesByTask]);

  const grouped = useMemo(() => {
    const today = startOfDay(new Date());
    const tomorrow = addDays(today, 1);
    const groups: Record<string, TaskRow[]> = {
      Overdue: [],
      Today: [],
      Tomorrow: [],
      "This week": [],
      Later: [],
      "No due date": [],
      Completed: [],
    };
    for (const t of filtered) {
      if (t.status === "complete") {
        groups.Completed.push(t);
        continue;
      }
      if (!t.due_date) {
        groups["No due date"].push(t);
        continue;
      }
      const d = startOfDay(new Date(t.due_date));
      if (isBefore(d, today)) groups.Overdue.push(t);
      else if (isSameDay(d, today)) groups.Today.push(t);
      else if (isSameDay(d, tomorrow)) groups.Tomorrow.push(t);
      else if (isBefore(d, addDays(today, 7))) groups["This week"].push(t);
      else groups.Later.push(t);
    }
    return groups;
  }, [filtered]);

  const toggleComplete = async (t: TaskRow, checked: boolean) => {
    if (!user) return;
    await supabase
      .from("tasks")
      .update({
        status: checked ? "complete" : "incomplete",
        completed_by: checked ? user.id : null,
        completed_at: checked ? (new Date().toISOString() as any) : null,
      })
      .eq("id", t.id);
    await supabase.from("task_history").insert({
      task_id: t.id,
      actor_id: user.id,
      event: checked ? "completed" : "reopened",
      detail: {},
    });
  };

  const overdueCount = grouped.Overdue.length;

  return (
    <AppShell>
      <PageContainer>
        <PageHeader
          title="Tasks"
          description="Workflow tasks, due dates, assignments, and comments."
          actions={
            <Button onClick={() => setNewOpen(true)}>
              <Plus className="h-4 w-4 mr-1.5" /> New task
            </Button>
          }
        />

        <div className="flex flex-wrap items-end gap-3 mb-4">
          <div className="flex-1 min-w-[200px]">
            <Label className="text-xs">Search</Label>
            <div className="relative">
              <Search className="h-3.5 w-3.5 absolute left-2.5 top-1/2 -translate-y-1/2 text-muted-foreground" />
              <Input
                value={query}
                onChange={(e) => setQuery(e.target.value)}
                placeholder="Filter tasks…"
                className="pl-8"
              />
            </div>
          </div>
          <div>
            <Label className="text-xs">Assigned To</Label>
            <Select value={filterAssignee} onValueChange={setFilterAssignee}>
              <SelectTrigger className="w-[180px]">
                <SelectValue />
              </SelectTrigger>
              <SelectContent>
                <SelectItem value="me">Me</SelectItem>
                <SelectItem value="all">Anyone</SelectItem>
                {profiles.map((p) => (
                  <SelectItem key={p.id} value={p.id}>{p.full_name || p.email}</SelectItem>
                ))}
              </SelectContent>
            </Select>
          </div>
          <div>
            <Label className="text-xs">Status</Label>
            <Select value={filterStatus} onValueChange={(v) => setFilterStatus(v as any)}>
              <SelectTrigger className="w-[160px]">
                <SelectValue />
              </SelectTrigger>
              <SelectContent>
                <SelectItem value="incomplete">Incomplete</SelectItem>
                <SelectItem value="complete">Complete</SelectItem>
                <SelectItem value="all">All</SelectItem>
              </SelectContent>
            </Select>
          </div>
          <div className="flex items-center gap-2 pb-1.5">
            <Switch id="mine" checked={showOnlyMine} onCheckedChange={setShowOnlyMine} />
            <Label htmlFor="mine" className="text-sm">Only created by me</Label>
          </div>
        </div>

        {overdueCount > 0 && (
          <div className="mb-4 flex items-center gap-2 text-sm text-destructive">
            <AlertCircle className="h-4 w-4" />
            {overdueCount} overdue task{overdueCount === 1 ? "" : "s"}
          </div>
        )}

        <div className="rounded-md border bg-card">
          {loading ? (
            <div className="p-6 text-sm text-muted-foreground">Loading…</div>
          ) : (
            Object.entries(grouped).map(([group, items]) =>
              items.length === 0 ? null : (
                <div key={group}>
                  <div
                    className={cn(
                      "px-4 py-2 text-xs font-semibold uppercase tracking-wider",
                      group === "Overdue"
                        ? "bg-destructive/10 text-destructive"
                        : "bg-muted/40 text-muted-foreground",
                    )}
                  >
                    {group} <span className="text-muted-foreground ml-1">{items.length}</span>
                  </div>
                  {items.map((t) => {
                    const ids = assigneesByTask[t.id] || [];
                    const c = t.case_id ? casesById[t.case_id] : null;
                    return (
                      <div
                        key={t.id}
                        className="flex items-center gap-3 px-4 py-2.5 border-t hover:bg-accent/40 cursor-pointer"
                        onClick={() => setOpenTaskId(t.id)}
                      >
                        <Checkbox
                          checked={t.status === "complete"}
                          onCheckedChange={(v) => toggleComplete(t, !!v)}
                          onClick={(e) => e.stopPropagation()}
                        />
                        <div className={cn("h-1.5 w-1.5 rounded-full", PRIORITY_DOT[t.priority])} />
                        <div className="flex-1 min-w-0">
                          <div className={cn("text-sm", t.status === "complete" && "line-through text-muted-foreground")}>
                            {t.title}
                          </div>
                          {c && (
                            <div className="text-[11px] text-muted-foreground truncate">
                              {c.case_number} — {c.title}
                            </div>
                          )}
                        </div>
                        {t.due_date && (
                          <div className="text-xs text-muted-foreground flex items-center gap-1">
                            <CalIcon className="h-3 w-3" />
                            {format(new Date(t.due_date), "MMM d")}
                          </div>
                        )}
                        <div className="flex -space-x-1.5">
                          {ids.slice(0, 3).map((uid) => {
                            const p = profilesById[uid];
                            return (
                              <Avatar key={uid} className="h-6 w-6 border-2 border-background">
                                <AvatarFallback className="text-[9px]">
                                  {p ? initials(p.full_name || p.email) : "?"}
                                </AvatarFallback>
                              </Avatar>
                            );
                          })}
                          {ids.length > 3 && (
                            <div className="h-6 w-6 rounded-full bg-muted border-2 border-background text-[9px] flex items-center justify-center">
                              +{ids.length - 3}
                            </div>
                          )}
                        </div>
                      </div>
                    );
                  })}
                </div>
              ),
            )
          )}
          {!loading && filtered.length === 0 && (
            <div className="p-12 text-center text-sm text-muted-foreground">
              No tasks match these filters.
            </div>
          )}
        </div>
      </PageContainer>

      <NewTaskDialog open={newOpen} onOpenChange={setNewOpen} onCreated={(id) => setOpenTaskId(id)} />
      <TaskDetailPanel
        taskId={openTaskId}
        open={!!openTaskId}
        onOpenChange={(v) => !v && setOpenTaskId(null)}
        onChanged={load}
      />
    </AppShell>
  );
}