<?php
/*************************************************************
# 076 License

Copyright (c) テクニカル諏訪子

Permission is hereby granted to any person obtaining a copy of the software
Little Beast (the "Software") to use, modify, merge, copy, publish, distribute,
sublicense, and/or sell copies of the Software, subject to the following conditions:

    1. **Origin Attribution**:
       - You must not misrepresent the origin of the Software; you must not claim
         you created the original Software.
       - If the Software is used in a product, you must either:
         a. Provide clear attribution in the product's documentation, user interface,
            or other visible areas, **OR**
         b. Pay the original developers a fee they specify in writing.
    2. **Usage Restriction**:
       - The Software, or any derivative works, dependencies, or libraries
         incorporating it, must not be used for censorship or to suppress freedom of
         speech, expression, or creativity. Prohibited uses include, but are not
         limited to:
         - Censorship of so-called "hate speech", visuals, non-mainstream opinions,
           ideas, or objective reality.
         - Tools or systems designed to restrict access to information or
           artistic works.
    3. **Notice Preservation**:
       - This license and the above copyright notice must remain intact in all copies
         of the source code.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
namespace Std\Lib\Db\Sqlite;

/**
 * PRAGMA integrity_check（ツリー・フリーリスト・インデックスの確認）
 */
final class Integrity {
  private array $used = [];
  private array $msgs = [];

  public function __construct(private Pager $pager, private Btree $bt, private Schema $schema) {}

  /**
   * @return array  問題のメッセージ（無ければ空）
   */
  public function check(): array {
    if ($this->pager->nPages === 0) return [];
    $this->tree(1, null);
    foreach ($this->schema->tables as $t) {
      if (($t['root'] ?? 0) > 1) $this->tree($t['root'], null);
    }
    foreach ($this->schema->indexes as $idx) $this->tree($idx['root'], $idx);
    $this->freelist();
    $lock = intdiv(0x40000000, $this->pager->pageSize) + 1;
    for ($p = 1; $p <= $this->pager->nPages; $p++) {
      if (!isset($this->used[$p]) && $p !== $lock) $this->msgs[] = "ページ{$p}は使われていません";
    }
    if (empty($this->msgs)) $this->indexes();
    return array_slice($this->msgs, 0, 100);
  }

  private function mark(int $p, string $what): bool {
    if ($p < 1 || $p > $this->pager->nPages) {
      $this->msgs[] = "{$what}：不正なページ番号{$p}";
      return false;
    }
    if (isset($this->used[$p])) {
      $this->msgs[] = "ページ{$p}が2回使われています（{$this->used[$p]}、{$what}）";
      return false;
    }
    $this->used[$p] = $what;
    return true;
  }

  private function tree(int $root, ?array $idx): void {
    $depths = [];
    $this->page($root, $idx, null, null, 0, $depths, $root);
    if (count(array_unique($depths)) > 1) $this->msgs[] = "ツリー{$root}：葉の深さが違います";
  }

  private function page(int $pgno, ?array $idx, mixed $lo, mixed $hi, int $depth, array &$depths, int $root): void {
    if (!$this->mark($pgno, "ツリー{$root}")) return;
    try {
      $p = $this->bt->page($pgno);
    } catch (\Throwable $e) {
      $this->msgs[] = "ページ{$pgno}：".$e->getMessage();
      return;
    }
    if ($p->isTable() !== ($idx === null)) {
      $this->msgs[] = "ページ{$pgno}：ツリーの種類が違います";
      return;
    }
    $n = count($p->cells);
    if ($n === 0 && $pgno !== $root && $p->isLeaf()) $this->msgs[] = "ページ{$pgno}：空の葉";
    $prev = $lo;
    for ($i = 0; $i <= $n; $i++) {
      $key = null;
      if ($i < $n) {
        try {
          $key = $p->isTable() ? $p->keys[$i] : $this->bt->key($p, $i);
        } catch (\Throwable $e) {
          $this->msgs[] = "ページ{$pgno}のセル{$i}：".$e->getMessage();
          continue;
        }
        $this->overflow($p, $i, $root);
      }
      if (!$p->isLeaf()) $this->page($i < $n ? $p->left[$i] : $p->right, $idx, $prev, $i < $n ? $key : $hi, $depth + 1, $depths, $root);
      if ($i === $n) break;
      if ($p->isTable()) {
        if ($prev !== null && ($p->isLeaf() ? $key <= $prev : $key < $prev)) $this->msgs[] = "ページ{$pgno}のセル{$i}：rowidの順番";
        if ($hi !== null && $key > $hi) $this->msgs[] = "ページ{$pgno}のセル{$i}：rowidが親より大きい";
      } else {
        if ($prev !== null && Record::compareKeys($key, $prev, $idx['colls'], $idx['desc']) <= 0) $this->msgs[] = "ページ{$pgno}のセル{$i}：キーの順番";
        if ($hi !== null && Record::compareKeys($key, $hi, $idx['colls'], $idx['desc']) >= 0) $this->msgs[] = "ページ{$pgno}のセル{$i}：キーが親より大きい";
      }
      $prev = $key;
    }
    if ($p->isLeaf()) $depths[] = $depth;
  }

  private function overflow(Page $p, int $i, int $root): void {
    if (!$p->isLeaf() && $p->isTable()) return;
    $c = $p->cells[$i];
    $pos = 0;
    $len = Record::getVarint($c, $pos);
    if ($p->isTable()) Record::getVarint($c, $pos);
    $local = $this->bt->localSize($len, $p->isTable());
    if ($len <= $local) return;
    $next = unpack('N', $c, $pos + $local)[1];
    $need = intdiv($len - $local + $this->pager->usable - 5, $this->pager->usable - 4);
    for ($k = 0; $k < $need; $k++) {
      if (!$this->mark($next, "オーバーフロー（ツリー{$root}）")) return;
      $next = unpack('N', $this->pager->read($next))[1];
    }
    if ($next !== 0) $this->msgs[] = "ツリー{$root}：オーバーフローが長過ぎます";
  }

  private function freelist(): void {
    $t = $this->pager->hdr['freeTrunk'];
    $count = 0;
    while ($t !== 0) {
      if (!$this->mark($t, 'フリーリスト')) return;
      $count++;
      $raw = $this->pager->read($t);
      $n = unpack('N', $raw, 4)[1];
      if ($n > intdiv($this->pager->usable, 4) - 2) {
        $this->msgs[] = "フリーリストのページ{$t}：数が不正です";
        return;
      }
      for ($i = 0; $i < $n; $i++) {
        $this->mark(unpack('N', $raw, 8 + $i * 4)[1], 'フリーリスト');
        $count++;
      }
      $t = unpack('N', $raw)[1];
    }
    if ($count !== $this->pager->hdr['freeCount']) $this->msgs[] = "フリーリストのページ数：{$count}（ヘッダー：{$this->pager->hdr['freeCount']}）";
  }

  /** インデックスとテーブルの行が合っているか */
  private function indexes(): void {
    foreach ($this->schema->indexes as $idx) {
      $t = $this->schema->tables[$idx['table']] ?? null;
      if (!$t || isset($t['unsupported'])) continue;
      $n = 0;
      foreach ($this->bt->indexScan($idx) as $key) {
        $n++;
        $rowid = end($key);
        $rec = $this->bt->get($t['root'], $rowid);
        if ($rec === null) {
          $this->msgs[] = "インデックス{$idx['name']}：行{$rowid}がテーブルにありません";
          continue;
        }
        $vals = Record::decode($rec);
        foreach ($idx['cols'] as $k => $ci) {
          $v = $ci === $t['ipk'] ? $rowid : ($vals[$ci] ?? null);
          if (Record::compare($v, $key[$k], 'BINARY') !== 0 && $vals[$ci] !== null) {
            $this->msgs[] = "インデックス{$idx['name']}：行{$rowid}の値が違います";
            break;
          }
        }
      }
      $rows = $this->bt->count($t['root']);
      if ($n !== $rows) $this->msgs[] = "インデックス{$idx['name']}：{$n}行（テーブルは{$rows}行）";
    }
  }
}