codetutor/frontend/src/app/patterns/[slug]/page.tsx

import type { Metadata } from "next";
import { notFound } from "next/navigation";
import { getPatternTutorial } from "@/lib/api";
import { Card, CardHeader, CardTitle, CardContent } from "@/components/ui/card";
import { CodeBlock } from "@/components/ui/code-block";
import { Markdown } from "@/components/ui/markdown";
import { Callout } from "@/components/ui/callout";
import { Badge } from "@/components/ui/badge";
import {
  CommonMistakesList,
  LearningProgression,
  PatternVariations,
  RecognitionSignals,
  RelatedPatterns,
} from "@/components/patterns";
import { PatternVisualization } from "@/components/visualization";
import { TwoPointersVisualization, PrefixSumVisualization, LinkedListVisualization, MonotonicStackVisualization, TreeTraversalVisualization, BFSVisualization, DFSVisualization, CoinChangeVisualization, BacktrackingVisualization, HeapVisualization } from "@/components/visualizations-new";
import { twoSumAlgorithm } from "@/content/algorithms/two-sum";
import { slidingWindowAlgorithm } from "@/content/algorithms/sliding-window";
import { binarySearchAlgorithm } from "@/content/algorithms/binary-search";
import { prefixSumAlgorithm } from "@/content/algorithms/prefix-sum";
import { fastSlowPointersAlgorithm } from "@/content/algorithms/fast-slow-pointers";
import { linkedListReversalAlgorithm } from "@/content/algorithms/linkedlist-reversal";
import { monotonicStackAlgorithm } from "@/content/algorithms/monotonic-stack";
import { treeTraversalAlgorithm } from "@/content/algorithms/tree-traversal";
import { bfsAlgorithm } from "@/content/algorithms/bfs";
import { dfsAlgorithm } from "@/content/algorithms/dfs";
import { coinChangeAlgorithm } from "@/content/algorithms/coin-change";
import { subsetsAlgorithm } from "@/content/algorithms/subsets";
import { kthLargestAlgorithm } from "@/content/algorithms/kth-largest";

interface PageProps {
  params: Promise<{ slug: string }>;
}

export async function generateMetadata({ params }: PageProps): Promise<Metadata> {
  const { slug } = await params;

  try {
    const pattern = await getPatternTutorial(slug);
    const description =
      pattern.description ||
      `Learn the ${pattern.name} pattern with ${pattern.question_count} practice problems.`;

    return {
      title: `${pattern.name} Pattern`,
      description,
      openGraph: {
        title: `${pattern.name} Pattern | CodeTutor`,
        description,
        type: "article",
      },
    };
  } catch {
    return {
      title: "Pattern Not Found",
    };
  }
}

export default async function PatternDetailPage({ params }: PageProps) {
  const { slug } = await params;

  let pattern;
  try {
    pattern = await getPatternTutorial(slug);
  } catch {
    notFound();
  }

  const difficultyLabels = ["Beginner", "Easy", "Intermediate", "Advanced", "Expert"];
  const difficultyLabel = pattern.difficulty_level
    ? difficultyLabels[pattern.difficulty_level - 1] || "Intermediate"
    : null;

  return (
    <div className="mx-auto space-y-8">
      {/* Header */}
      <div>
        <div className="flex items-center gap-3 mb-2">
          <h1 className="text-3xl font-bold">{pattern.name}</h1>
          {difficultyLabel && (
            <Badge variant="outline">{difficultyLabel}</Badge>
          )}
        </div>
        <p className="text-[var(--muted-foreground)]">
          {pattern.question_count} questions using this pattern
        </p>
      </div>

      {/* Description */}
      {pattern.description && (
        <Card>
          <CardHeader>
            <CardTitle>What is {pattern.name}?</CardTitle>
          </CardHeader>
          <CardContent>
            <Markdown>{pattern.description}</Markdown>
          </CardContent>
        </Card>
      )}

      {/* Metaphor - The relatable analogy */}
      {pattern.metaphor && (
        <Callout variant="insight" title="Think of it like this...">
          <Markdown>{pattern.metaphor}</Markdown>
        </Callout>
      )}

      {/* Core Concept - The "aha!" insight */}
      {pattern.core_concept && (
        <Card>
          <CardHeader>
            <CardTitle>Core Concept</CardTitle>
          </CardHeader>
          <CardContent>
            <Markdown>{pattern.core_concept}</Markdown>
          </CardContent>
        </Card>
      )}

      {/* Interactive Visualization */}
      {slug === "two-pointers" ? (
        <TwoPointersVisualization algorithm={twoSumAlgorithm} />
      ) : slug === "sliding-window" ? (
        <TwoPointersVisualization algorithm={slidingWindowAlgorithm} />
      ) : slug === "binary-search" ? (
        <TwoPointersVisualization algorithm={binarySearchAlgorithm} />
      ) : slug === "prefix-sum" ? (
        <PrefixSumVisualization algorithm={prefixSumAlgorithm} />
      ) : slug === "fast-slow-pointers" ? (
        <LinkedListVisualization algorithm={fastSlowPointersAlgorithm} />
      ) : slug === "linkedlist-reversal" ? (
        <LinkedListVisualization algorithm={linkedListReversalAlgorithm} />
      ) : slug === "monotonic-stack" ? (
        <MonotonicStackVisualization algorithm={monotonicStackAlgorithm} />
      ) : slug === "tree-traversal" ? (
        <TreeTraversalVisualization algorithm={treeTraversalAlgorithm} />
      ) : slug === "bfs" ? (
        <BFSVisualization algorithm={bfsAlgorithm} />
      ) : slug === "dfs" ? (
        <DFSVisualization algorithm={dfsAlgorithm} />
      ) : slug === "dynamic-programming" ? (
        <CoinChangeVisualization algorithm={coinChangeAlgorithm} />
      ) : slug === "backtracking" ? (
        <BacktrackingVisualization algorithm={subsetsAlgorithm} />
      ) : slug === "heap" ? (
        <HeapVisualization algorithm={kthLargestAlgorithm} />
      ) : pattern.visualization_examples && pattern.visualization_examples.length > 0 ? (
        <Card>
          <CardHeader>
            <CardTitle>Interactive Visualization</CardTitle>
          </CardHeader>
          <CardContent>
            <PatternVisualization examples={pattern.visualization_examples} />
          </CardContent>
        </Card>
      ) : null}

      {/* Static Visualization - ASCII diagram walkthrough (fallback) */}
      {pattern.visualization && (
        <Card>
          <CardHeader>
            <CardTitle>Visual Walkthrough</CardTitle>
          </CardHeader>
          <CardContent>
            <Markdown>{pattern.visualization}</Markdown>
          </CardContent>
        </Card>
      )}

      {/* Code Template */}
      {pattern.code_template && (
        <Card>
          <CardHeader>
            <CardTitle>Code Template</CardTitle>
          </CardHeader>
          <CardContent>
            <p className="text-sm text-[var(--muted-foreground)] mb-4">
              Use this skeleton as a starting point for problems using this pattern:
            </p>
            <CodeBlock
              code={pattern.code_template}
              language="python"
              label="Pattern code template"
            />
          </CardContent>
        </Card>
      )}

      {/* Recognition Signals */}
      {pattern.recognition_signals && pattern.recognition_signals.length > 0 && (
        <RecognitionSignals signals={pattern.recognition_signals} />
      )}

      {/* When to Use */}
      {pattern.when_to_use && (
        <Card>
          <CardHeader>
            <CardTitle>When to Use</CardTitle>
          </CardHeader>
          <CardContent>
            <Markdown>{pattern.when_to_use}</Markdown>
          </CardContent>
        </Card>
      )}

      {/* Common Mistakes */}
      {pattern.common_mistakes && pattern.common_mistakes.length > 0 && (
        <CommonMistakesList mistakes={pattern.common_mistakes} />
      )}

      {/* Pattern Variations */}
      {pattern.variations && pattern.variations.length > 0 && (
        <PatternVariations variations={pattern.variations} />
      )}

      {/* Learning Progression */}
      {pattern.learning_progression && (
        <LearningProgression progression={pattern.learning_progression} />
      )}

      {/* Related Patterns */}
      <div className="grid md:grid-cols-2 gap-6">
        {pattern.prerequisite_patterns && pattern.prerequisite_patterns.length > 0 && (
          <RelatedPatterns
            title="Prerequisites"
            description="Learn these patterns first:"
            patterns={pattern.prerequisite_patterns}
          />
        )}
        {pattern.related_patterns && pattern.related_patterns.length > 0 && (
          <RelatedPatterns
            title="Related Patterns"
            description="Explore similar techniques:"
            patterns={pattern.related_patterns}
          />
        )}
      </div>
    </div>
  );
}