"use client";

import { useId, useMemo, useState } from "react";
import type { StageSectionConfig, SelectOption } from "@/types/form";
import type { UseFormRegister, FieldValues, FieldErrors } from "react-hook-form";
import { FieldRenderer } from "./fields/FieldRenderer";
import { MatrixGroup } from "./MatrixGroup";
import { evaluate } from "@/lib/conditional";

interface StageSectionProps {
  section: StageSectionConfig;
  register: UseFormRegister<FieldValues>;
  errors: FieldErrors;
  /** Live form values, used to evaluate per-field visibility rules. */
  formValues: Record<string, unknown>;
  /** Whether this is the section that matches the current org stage (for the "current" badge). */
  isCurrent: boolean;
  /** Whether the section starts open. */
  defaultOpen: boolean;
  /** Option groups fetched from CiviCRM, keyed by option_group_id. */
  options: Record<number, SelectOption[]>;
}

/**
 * One accordion card per stage section. Renders all fields whose individual
 * visibility rules pass. The section's own visibility is decided by the
 * parent EngagementForm; if rendered, it's visible.
 */
export function StageSection({
  section,
  register,
  errors,
  formValues,
  isCurrent,
  defaultOpen,
  options,
}: StageSectionProps) {
  const [open, setOpen] = useState(defaultOpen);
  const headingId = useId();
  const panelId = useId();

  // Names of fields that appear inside any matrix group; excluded from the
  // standalone per-field grid so they don't render twice.
  const matrixFieldNames = useMemo(() => {
    const names = new Set<string>();
    for (const m of section.matrixGroups ?? []) {
      for (const row of m.rows) for (const f of row.fields) names.add(f);
    }
    return names;
  }, [section.matrixGroups]);

  const visibleFields = section.fields.filter(
    (f) => evaluate(f.visibleWhen, formValues) && !matrixFieldNames.has(f.name),
  );

  return (
    <section
      aria-labelledby={headingId}
      className={
        "overflow-hidden rounded-xl border bg-white shadow-sm transition " +
        (isCurrent
          ? "border-leaf-300 ring-1 ring-leaf-200"
          : "border-stone-200")
      }
    >
      <h2 id={headingId} className="m-0">
        <button
          type="button"
          onClick={() => setOpen((v) => !v)}
          aria-expanded={open}
          aria-controls={panelId}
          className={
            "group flex w-full items-center justify-between gap-4 px-5 py-4 text-left " +
            "focus:outline-none focus-visible:ring-2 focus-visible:ring-leaf-500/40 " +
            (isCurrent ? "bg-leaf-50" : "bg-stone-50 hover:bg-stone-100")
          }
        >
          <span className="flex items-center gap-3">
            <RankBadge rank={section.rank} isCurrent={isCurrent} />
            <span className="flex flex-col">
              <span className="text-base font-semibold text-stone-900">{section.label}</span>
              {isCurrent && (
                <span className="text-xs font-medium uppercase tracking-wide text-leaf-700">
                  Current stage
                </span>
              )}
            </span>
          </span>
          <Chevron open={open} />
        </button>
      </h2>

      <div
        id={panelId}
        role="region"
        aria-labelledby={headingId}
        hidden={!open}
        className="border-t border-stone-100"
      >
        <div className="px-5 py-5 sm:px-6 sm:py-6">
          {section.intro && (
            <p className="mb-5 text-sm text-stone-600 leading-relaxed">{section.intro}</p>
          )}
          {(section.matrixGroups ?? []).length > 0 && (
            <div className="mb-6 space-y-5">
              {section.matrixGroups!.map((g) => (
                <MatrixGroup key={g.id} group={g} register={register} />
              ))}
            </div>
          )}
          {visibleFields.length === 0 && (section.matrixGroups ?? []).length === 0 ? (
            <p className="text-sm italic text-stone-500">No fields are visible at this stage.</p>
          ) : visibleFields.length === 0 ? null : (
            <div className="grid grid-cols-1 gap-x-6 gap-y-5 md:grid-cols-2">
              {visibleFields.map((f) => {
                const resolvedOptions = f.optionGroupId ? options[f.optionGroupId] : undefined;
                const wide =
                  f.type === "textarea" ||
                  f.type === "boolean" ||
                  f.type === "multiselect";
                return (
                  <div key={f.name} className={wide ? "md:col-span-2" : ""}>
                    <FieldRenderer
                      field={f}
                      register={register}
                      errors={errors}
                      readonlyValue={formValues[f.name]}
                      resolvedOptions={resolvedOptions}
                    />
                  </div>
                );
              })}
            </div>
          )}
        </div>
      </div>
    </section>
  );
}

function RankBadge({ rank, isCurrent }: { rank: number; isCurrent: boolean }) {
  return (
    <span
      aria-hidden
      className={
        "inline-flex h-9 w-9 items-center justify-center rounded-full text-sm font-semibold " +
        (isCurrent
          ? "bg-leaf-600 text-white"
          : "bg-stone-200 text-stone-700")
      }
    >
      {rank}
    </span>
  );
}

function Chevron({ open }: { open: boolean }) {
  return (
    <svg
      aria-hidden
      viewBox="0 0 20 20"
      fill="currentColor"
      className={"h-5 w-5 text-stone-500 transition-transform " + (open ? "rotate-180" : "")}
    >
      <path
        fillRule="evenodd"
        d="M5.23 7.21a.75.75 0 011.06.02L10 11.06l3.71-3.83a.75.75 0 111.08 1.04l-4.25 4.39a.75.75 0 01-1.08 0L5.21 8.27a.75.75 0 01.02-1.06z"
        clipRule="evenodd"
      />
    </svg>
  );
}