package unit;

import java.util.*;

/**
 * Standalone unit tests for pandas CWE-407 defects.
 *
 * pandas-0001: Styler render — O(R×H) hidden_rows list membership in render loops
 *   Simulates: [r for r in range(len(index)) if r not in self.hidden_rows]
 *   and the body-cell loop: if r not in self.hidden_rows (O(H) per row).
 *   slow(): list.contains(r) per row iteration — O(R×H)
 *   fast(): HashSet.contains(r) per row iteration — O(R)
 *   Assert: slowOps >= fastOps * 10 for R=2000 rows, H=500 hidden rows
 */
public class PandasTest {

    // ── pandas-0001 ───────────────────────────────────────────────────────────

    /**
     * Slow path: hidden rows stored as a List<Integer>.
     * Each membership test scans up to H entries — O(H) per row.
     * Total for R rows: O(R × H).
     *
     * @param totalRows   total row count R
     * @param hiddenRows  set of hidden row indices (stored as list)
     * @return op count (each element comparison in list.contains() = 1 op)
     */
    static long slowRenderRows(int totalRows, List<Integer> hiddenRows) {
        long ops = 0;
        List<Integer> visibleRows = new ArrayList<>();

        for (int r = 0; r < totalRows; r++) {
            // Mirrors: if r not in self.hidden_rows — linear scan
            boolean found = false;
            for (int i = 0; i < hiddenRows.size(); i++) {
                ops++;
                if (hiddenRows.get(i) == r) {
                    found = true;
                    break;
                }
            }
            if (!found) {
                visibleRows.add(r);
            }
        }
        return ops;
    }

    /**
     * Fast path: hidden rows stored as a HashSet<Integer>.
     * Each membership test is O(1). Total for R rows: O(R + H).
     *
     * @param totalRows   total row count R
     * @param hiddenRows  set of hidden row indices (stored as list — converted once)
     * @return op count (1 op per row for set.contains + 1 op per hidden row to build set)
     */
    static long fastRenderRows(int totalRows, List<Integer> hiddenRows) {
        long ops = 0;
        List<Integer> visibleRows = new ArrayList<>();

        // Build set once: O(H)
        Set<Integer> hiddenSet = new HashSet<>(hiddenRows.size() * 2);
        for (int h : hiddenRows) {
            hiddenSet.add(h);
            ops++;
        }

        for (int r = 0; r < totalRows; r++) {
            ops++;                              // O(1) set.contains
            if (!hiddenSet.contains(r)) {
                visibleRows.add(r);
            }
        }
        return ops;
    }

    static void testRenderRows() {
        int R = 2000;   // total rows
        int H = 500;    // hidden rows (scattered through the middle — maximizes scan depth)

        List<Integer> hiddenRows = new ArrayList<>(H);
        // Hidden rows in the range [R/4, R/4+H) — they appear late in the list
        for (int i = R / 4; i < R / 4 + H; i++) hiddenRows.add(i);

        long slowOps = slowRenderRows(R, hiddenRows);
        long fastOps = fastRenderRows(R, hiddenRows);

        System.out.printf(
            "pandas-0001  R=%-5d H=%-4d  slowOps=%-8d  fastOps=%-6d  ratio=%.1fx%n",
            R, H, slowOps, fastOps, (double) slowOps / fastOps
        );

        assert slowOps > fastOps * 10 :
            "pandas-0001 FAIL: expected slowOps > 10×fastOps, got " + slowOps + " vs " + fastOps;
        System.out.println("pandas-0001  PASS");
    }

    // ── main ──────────────────────────────────────────────────────────────────

    public static void main(String[] args) {
        int pass = 0, total = 1;

        try { testRenderRows(); pass++; } catch (AssertionError e) { System.err.println(e.getMessage()); }

        System.out.printf("%n%d/%d PASS%n", pass, total);
        if (pass != total) System.exit(1);
    }
}