"use client";

import { ChevronDown, ChevronRight } from "lucide-react";
import Link from "next/link";
import { useCallback, useMemo, useState, type ReactNode } from "react";
import { SegmentedControl } from "@/components/ui/SegmentedControl";
import type { OpenPositionResolved } from "@/lib/positions";
import { LazyGraphOrgChart } from "./LazyGraphOrgChart";
import type { ChartNode, OrgDepartment, OrgDivision, OrgEmployee, OrgTeam } from "./types";

type ViewMode = "list" | "graph";

function TreeRow({
  depth,
  expandable,
  expandedNow,
  onToggle,
  children,
}: {
  depth: number;
  expandable: boolean;
  expandedNow: boolean;
  onToggle: () => void;
  children: ReactNode;
}) {
  return (
    <div className="flex items-center gap-2 rounded px-2 py-1.5 hover:bg-surface" style={{ paddingLeft: depth * 24 + 8 }}>
      {expandable ? (
        <button type="button" onClick={onToggle} className="shrink-0 text-ink-muted">
          {expandedNow ? <ChevronDown className="h-4 w-4" /> : <ChevronRight className="h-4 w-4" />}
        </button>
      ) : (
        <span className="w-4 shrink-0" />
      )}
      {children}
    </div>
  );
}

type PositionTreeProps = {
  employees: OrgEmployee[];
  divisions: OrgDivision[];
  departments: OrgDepartment[];
  teams: OrgTeam[];
  openPositions: OpenPositionResolved[];
};

export function PositionTree({ employees, divisions, departments, teams, openPositions }: PositionTreeProps) {
  const [expanded, setExpanded] = useState<Set<string>>(new Set(["root"]));
  const [mode, setMode] = useState<ViewMode>("list");

  // useCallback-stable: GraphOrgChart's layout memo depends on these
  // references, so unstable functions would force a Dagre re-layout on
  // every unrelated re-render.
  const toggle = useCallback((id: string) => {
    setExpanded((prev) => {
      const next = new Set(prev);
      if (next.has(id)) next.delete(id);
      else next.add(id);
      return next;
    });
  }, []);

  const isExpanded = useCallback((id: string) => expanded.has(id), [expanded]);

  const ceo = employees.find((e) => e.org_level === 0) ?? null;
  const { divisionHeadByDivision, teamLeadByTeam, icsByTeamAndTitle } = useMemo(() => {
    const divisionHeadByDivision = new Map<string, OrgEmployee>();
    const teamLeadByTeam = new Map<string, OrgEmployee>();
    const icsByTeamAndTitle = new Map<string, Map<string, OrgEmployee[]>>();
    for (const e of employees) {
      if (e.org_level === 1 && e.division_id) divisionHeadByDivision.set(e.division_id, e);
      if (e.is_lead && e.team_id) teamLeadByTeam.set(e.team_id, e);
      if (!e.is_lead && e.org_level === 3 && e.team_id) {
        if (!icsByTeamAndTitle.has(e.team_id)) icsByTeamAndTitle.set(e.team_id, new Map());
        const byTitle = icsByTeamAndTitle.get(e.team_id)!;
        if (!byTitle.has(e.job_title)) byTitle.set(e.job_title, []);
        byTitle.get(e.job_title)!.push(e);
      }
    }
    return { divisionHeadByDivision, teamLeadByTeam, icsByTeamAndTitle };
  }, [employees]);
  const openByTeam = useMemo(() => {
    const map = new Map<string, OpenPositionResolved[]>();
    for (const p of openPositions) {
      if (!map.has(p.team_id)) map.set(p.team_id, []);
      map.get(p.team_id)!.push(p);
    }
    return map;
  }, [openPositions]);

  // Mirrors the JSX walk below into the generic ChartNode shape for graph
  // mode — same synthetic ids ("root", div-*, dept-*, team-*, teamKey-title)
  // the list already uses as `expanded` keys, so one Set drives both.
  const chartTree = useMemo<ChartNode[]>(() => {
    if (!ceo) return [];

    function buildTeam(team: OrgTeam): ChartNode {
      const teamKey = `team-${team.id}`;
      const lead = teamLeadByTeam.get(team.id);
      const icsByTitle = icsByTeamAndTitle.get(team.id) ?? new Map<string, OrgEmployee[]>();
      const openForTeam = openByTeam.get(team.id) ?? [];

      const titleGroups: ChartNode[] = Array.from(icsByTitle.entries()).map(([title, people]) => ({
        id: `${teamKey}-${title}`,
        kind: "group",
        label: title,
        sublabel: `${people.length}x besetzt`,
        children: people.map((p) => ({
          id: p.id,
          kind: "person",
          label: `${p.first_name} ${p.last_name}`,
          href: `/employees/${p.id}`,
          avatar: { firstName: p.first_name, lastName: p.last_name },
          children: [],
        })),
      }));

      const vacancyNodes: ChartNode[] = openForTeam.map((p) => ({
        id: `vac-${p.id}`,
        kind: "vacancy",
        label: `${p.position_number} · ${p.title}`,
        href: "/positions",
        children: [],
      }));

      return {
        id: teamKey,
        kind: "role",
        label: `Teamleitung ${team.name}`,
        sublabel: lead ? `besetzt: ${lead.first_name} ${lead.last_name}` : "vakant",
        vacant: !lead,
        children: [...titleGroups, ...vacancyNodes],
      };
    }

    function buildDept(dept: OrgDepartment): ChartNode {
      return {
        id: `dept-${dept.id}`,
        kind: "group",
        label: `${dept.org_number} · ${dept.name}`,
        children: teams.filter((t) => t.department_id === dept.id).map(buildTeam),
      };
    }

    function buildDivision(div: OrgDivision): ChartNode {
      const head = divisionHeadByDivision.get(div.id);
      return {
        id: `div-${div.id}`,
        kind: "role",
        label: `Bereichsleitung ${div.name}`,
        sublabel: head ? `besetzt: ${head.first_name} ${head.last_name}` : "vakant",
        vacant: !head,
        children: departments.filter((d) => d.division_id === div.id).map(buildDept),
      };
    }

    return [
      {
        id: "root",
        kind: "role",
        label: "Geschäftsführung",
        sublabel: `besetzt: ${ceo.first_name} ${ceo.last_name}`,
        children: divisions.map(buildDivision),
      },
    ];
  }, [ceo, divisionHeadByDivision, teamLeadByTeam, icsByTeamAndTitle, openByTeam, divisions, departments, teams]);

  return (
    <div className="flex flex-col gap-4">
      <div className="flex justify-end">
        <SegmentedControl<ViewMode> value={mode} onChange={setMode} options={[{ value: "list", label: "Liste" }, { value: "graph", label: "Grafisch" }]} />
      </div>
      {mode === "graph" ? (
        <LazyGraphOrgChart tree={chartTree} isExpanded={isExpanded} onToggle={toggle} />
      ) : (
        <div className="rounded border border-border bg-white p-4">
      {ceo && (
        <TreeRow depth={0} expandable expandedNow={expanded.has("root")} onToggle={() => toggle("root")}>
          <span className="text-sm font-semibold text-ink">Geschäftsführung</span>
          <span className="text-xs text-ink-muted">
            besetzt: {ceo.first_name} {ceo.last_name}
          </span>
        </TreeRow>
      )}
      {expanded.has("root") &&
        divisions.map((div) => {
          const head = divisionHeadByDivision.get(div.id);
          const divKey = `div-${div.id}`;
          return (
            <div key={div.id}>
              <TreeRow depth={1} expandable expandedNow={expanded.has(divKey)} onToggle={() => toggle(divKey)}>
                <span className="text-sm font-semibold text-ink">Bereichsleitung {div.name}</span>
                <span className="text-xs text-ink-muted">{head ? `besetzt: ${head.first_name} ${head.last_name}` : "vakant"}</span>
              </TreeRow>
              {expanded.has(divKey) &&
                departments
                  .filter((d) => d.division_id === div.id)
                  .map((dept) => {
                    const deptKey = `dept-${dept.id}`;
                    return (
                      <div key={dept.id}>
                        <TreeRow depth={2} expandable expandedNow={expanded.has(deptKey)} onToggle={() => toggle(deptKey)}>
                          <span className="text-sm text-ink">
                            {dept.org_number} · {dept.name}
                          </span>
                        </TreeRow>
                        {expanded.has(deptKey) &&
                          teams
                            .filter((t) => t.department_id === dept.id)
                            .map((team) => {
                              const teamKey = `team-${team.id}`;
                              const lead = teamLeadByTeam.get(team.id);
                              const icsByTitle = icsByTeamAndTitle.get(team.id) ?? new Map<string, OrgEmployee[]>();
                              const openForTeam = openByTeam.get(team.id) ?? [];
                              return (
                                <div key={team.id}>
                                  <TreeRow depth={3} expandable expandedNow={expanded.has(teamKey)} onToggle={() => toggle(teamKey)}>
                                    <span className="text-sm text-ink">Teamleitung {team.name}</span>
                                    <span className="text-xs text-ink-muted">
                                      {lead ? `besetzt: ${lead.first_name} ${lead.last_name}` : "vakant"}
                                    </span>
                                  </TreeRow>
                                  {expanded.has(teamKey) && (
                                    <>
                                      {Array.from(icsByTitle.entries()).map(([title, people]) => {
                                        const groupKey = `${teamKey}-${title}`;
                                        return (
                                          <div key={title}>
                                            <TreeRow
                                              depth={4}
                                              expandable={people.length > 0}
                                              expandedNow={expanded.has(groupKey)}
                                              onToggle={() => toggle(groupKey)}
                                            >
                                              <span className="text-sm text-ink">{title}</span>
                                              <span className="text-xs text-ink-muted">{people.length}x besetzt</span>
                                            </TreeRow>
                                            {expanded.has(groupKey) &&
                                              people.map((p) => (
                                                <div key={p.id} className="py-1" style={{ paddingLeft: 5 * 24 + 8 }}>
                                                  <Link href={`/employees/${p.id}`} className="text-sm text-ink-body hover:text-brand-700 hover:underline">
                                                    {p.first_name} {p.last_name}
                                                  </Link>
                                                </div>
                                              ))}
                                          </div>
                                        );
                                      })}
                                      {openForTeam.map((p) => (
                                        <Link
                                          key={p.id}
                                          href="/positions"
                                          className="block border-l-2 border-dashed border-brand-200 py-1 text-sm text-brand-700 hover:underline"
                                          style={{ paddingLeft: 4 * 24 + 8 }}
                                        >
                                          + {p.position_number} · {p.title}
                                        </Link>
                                      ))}
                                    </>
                                  )}
                                </div>
                              );
                            })}
                      </div>
                    );
                  })}
            </div>
          );
        })}
        </div>
      )}
    </div>
  );
}