"use client";

// ─── Chapter Intelligence Header ──────────────────────────────────────────────
// Surfaces exam intelligence from curriculum metadata above lesson content.
// Renders nothing if chapter cannot be matched (graceful degradation).

import { Clock, Flame, Star, BookMarked, AlertTriangle } from "lucide-react";
import { searchChapters } from "@/lib/curriculum/index";
import {
  getExamProfile,
  pyqLabel,
  difficultyLabel,
} from "@/lib/curriculum/exam-intelligence";

import { cn } from "@/lib/utils";

// ─── Helpers ──────────────────────────────────────────────────────────────────

function normalizeLevel(raw: string | null | undefined): string | undefined {
  if (!raw) return undefined;
  const s = raw.toLowerCase();
  if (s.includes("sslc") || s.includes("10")) return "SSLC";
  if (s.includes("+2") || s.includes("12") || s.includes("plus two") || s.includes("class 12")) return "+2";
  if (s.includes("+1") || s.includes("11") || s.includes("plus one") || s.includes("class 11")) return "+1";
  return undefined;
}

// ─── Sub-components ───────────────────────────────────────────────────────────

function IntelChip({
  children,
  variant = "neutral",
}: {
  children: React.ReactNode;
  variant?: "neutral" | "green" | "amber" | "violet" | "red";
}) {
  const variants = {
    neutral: "border-white/[0.08] bg-white/[0.04] text-white/50",
    green:   "border-emerald-400/20 bg-emerald-400/8 text-emerald-400",
    amber:   "border-amber-400/20 bg-amber-400/8 text-amber-400",
    violet:  "border-violet-400/20 bg-violet-400/8 text-violet-400",
    red:     "border-red-400/20 bg-red-400/8 text-red-400",
  };
  return (
    <span
      className={cn(
        "inline-flex items-center gap-1 rounded-full border px-2.5 py-0.5 text-[11px] font-medium",
        variants[variant],
      )}
    >
      {children}
    </span>
  );
}

// ─── Main component ───────────────────────────────────────────────────────────

type Props = {
  /** Chapter name or topic extracted from study request analysis */
  chapterQuery: string;
  /** Level hint: "+1", "+2", "SSLC", grade string, or exam string */
  levelHint?: string | null;
};

export function ChapterIntelHeader({ chapterQuery, levelHint }: Props) {
  if (!chapterQuery) return null;

  const level = normalizeLevel(levelHint);
  const results = searchChapters(chapterQuery, { level, limit: 1 });
  if (results.length === 0) return null;

  const { chapter, level: foundLevel, subjectSlug } = results[0];
  const profile = getExamProfile(chapter);

  const priorityVariant: "green" | "amber" | "violet" | "red" =
    profile.priority === "critical" ? "red"
    : profile.priority === "important" ? "amber"
    : profile.priority === "moderate" ? "violet"
    : "neutral" as "violet";

  const priorityLabel =
    profile.priority === "critical" ? "Exam critical"
    : profile.priority === "important" ? "High priority"
    : profile.priority === "moderate" ? "Worth studying"
    : "Low priority";

  return (
    <div className="rounded-xl border border-white/[0.07] bg-white/[0.025] px-4 py-3.5">
      {/* Top row: chapter identity */}
      <div className="flex flex-wrap items-center gap-2">
        <span className="text-[12px] font-semibold text-white/70">{chapter.name}</span>
        <span className="text-white/25">·</span>
        <span className="text-[11px] text-white/40">{foundLevel} {subjectSlug.charAt(0).toUpperCase() + subjectSlug.slice(1)}</span>
      </div>

      {/* Badge row */}
      <div className="mt-2.5 flex flex-wrap gap-1.5">
        {/* Priority */}
        <IntelChip variant={priorityVariant}>
          <Flame className="size-2.5" />
          {priorityLabel}
        </IntelChip>

        {/* PYQ frequency */}
        <IntelChip variant={chapter.pyqFrequency === "very_high" || chapter.pyqFrequency === "high" ? "amber" : "neutral"}>
          <Star className="size-2.5" />
          {pyqLabel(chapter)}
        </IntelChip>

        {/* Difficulty */}
        <IntelChip variant={chapter.difficultyScore <= 3 ? "green" : "neutral"}>
          {difficultyLabel(chapter)}
        </IntelChip>

        {/* Study time */}
        <IntelChip variant="neutral">
          <Clock className="size-2.5" />
          {chapter.estimatedMinutes} min
        </IntelChip>

        {/* Formulas count */}
        {chapter.formulas && chapter.formulas.length > 0 ? (
          <IntelChip variant="violet">
            <BookMarked className="size-2.5" />
            {chapter.formulas.length} formula{chapter.formulas.length !== 1 ? "s" : ""}
          </IntelChip>
        ) : null}

        {/* Last night priority */}
        {chapter.lastNightPriority >= 4 ? (
          <IntelChip variant="green">
            <AlertTriangle className="size-2.5" />
            Study tonight
          </IntelChip>
        ) : null}
      </div>

      {/* Insight line */}
      <p className="mt-2 text-[11.5px] leading-relaxed text-white/40">
        {profile.action}
        {chapter.examWeightageMarks
          ? ` · ~${chapter.examWeightageMarks} marks in theory paper`
          : null}
      </p>

      {/* Prerequisites */}
      {chapter.prerequisites.length > 0 ? (
        <div className="mt-2.5 flex flex-wrap items-center gap-1.5">
          <span className="text-[10.5px] text-white/28">Before this, revise:</span>
          {chapter.prerequisites.map((prereq) => (
            <span
              key={prereq}
              className="rounded-full border border-white/[0.06] bg-white/[0.03] px-2 py-0.5 text-[10.5px] text-white/40"
            >
              {prereq}
            </span>
          ))}
        </div>
      ) : null}

      {/* Top formulas preview */}
      {chapter.formulas && chapter.formulas.length > 0 ? (
        <div className="mt-2.5 flex flex-wrap gap-1.5">
          {chapter.formulas.slice(0, 3).map((f) => (
            <code
              key={f}
              className="rounded border border-amber-400/15 bg-amber-400/5 px-2 py-0.5 font-mono text-[10.5px] text-amber-400/80"
            >
              {f}
            </code>
          ))}
          {chapter.formulas.length > 3 ? (
            <span className="text-[10.5px] text-white/28">+{chapter.formulas.length - 3} more</span>
          ) : null}
        </div>
      ) : null}
    </div>
  );
}