//===-- SQLiteBuildDB.cpp -------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#include "llbuild/Core/BuildDB.h"

#include "llbuild/Basic/BinaryCoding.h"
#include "llbuild/Basic/PlatformUtility.h"
#include "llbuild/Core/BuildEngine.h"

#include "llvm/ADT/STLExtras.h"

#include <cassert>
#include <cerrno>
#include <cstring>
#include <mutex>
#include <sstream>

#include <sqlite3.h>

using namespace llbuild;
using namespace llbuild::core;

// SQLite BuildDB Implementation

namespace {

class SQLiteBuildDB : public BuildDB {
  /// Version History:
  /// * 7: De-normalized the rule result dependencies.
  /// * 6: Added `ordinal` field for dependencies.
  /// * 5: Switched to using `WITHOUT ROWID` for dependencies.
  /// * 4: Pre-history
  static const int currentSchemaVersion = 7;

  sqlite3 *db = nullptr;

  /// The mutex to protect all access to the database and statements.
  std::mutex dbMutex;

  std::string getCurrentErrorMessage() {
    int err_code = sqlite3_errcode(db);
    const char* err_message = sqlite3_errmsg(db);
    const char* filename = sqlite3_db_filename(db, "main");

    std::stringstream out;
    out << "error: accessing build database \"" << filename << "\": " << err_message;

    if (err_code == SQLITE_BUSY || err_code == SQLITE_LOCKED) {
      out << " Possibly there are two concurrent builds running in the same filesystem location.";
    }

    return out.str();
  }

public:
  virtual ~SQLiteBuildDB() {
    if (db)
      close();
  }

  bool open(StringRef path, uint32_t clientSchemaVersion,
            std::string *error_out) {
    std::lock_guard<std::mutex> guard(dbMutex);
    assert(!db);

    // Configure SQLite3 on first use.
    //
    // We attempt to set multi-threading mode, but can settle for serialized if
    // the library can't be reinitialized (there are only two modes).
    static int sqliteConfigureResult = []() -> int {
      // We access a single connection from multiple threads.
      return sqlite3_config(SQLITE_CONFIG_MULTITHREAD);
    }();
    if (sqliteConfigureResult != SQLITE_OK) {
        if (!sqlite3_threadsafe()) {
            *error_out = "unable to configure database: not thread-safe";
            return false;
        }
    }

    int result = sqlite3_open(path.str().c_str(), &db);
    if (result != SQLITE_OK) {
      *error_out = "unable to open database: " + std::string(
          sqlite3_errstr(result));
      return false;
    }

    // Create the database schema, if necessary.
    char *cError;
    int version;
    uint32_t clientVersion = 0;
    sqlite3_stmt* stmt;
    result = sqlite3_prepare_v2(
      db, "SELECT version,client_version FROM info LIMIT 1",
      -1, &stmt, nullptr);
    if (result == SQLITE_ERROR) {
      version = -1;
    } else {
      if (result != SQLITE_OK) {
        *error_out = getCurrentErrorMessage();
        return false;
      }
      result = sqlite3_step(stmt);
      if (result == SQLITE_DONE) {
        version = -1;
      } else if (result == SQLITE_ROW) {
        assert(sqlite3_column_count(stmt) == 2);
        version = sqlite3_column_int(stmt, 0);
        clientVersion = sqlite3_column_int(stmt, 1);
      } else {
        *error_out = getCurrentErrorMessage();
        return false;
      }
      sqlite3_finalize(stmt);
    }

    if (version != currentSchemaVersion ||
        clientVersion != clientSchemaVersion) {
      // Close the database before we try to recreate it.
      sqlite3_close(db);

      // Always recreate the database from scratch when the schema changes.
      result = basic::sys::unlink(path.str().c_str());
      if (result == -1) {
        if (errno != ENOENT) {
          *error_out = std::string("unable to unlink existing database: ") +
            ::strerror(errno);
          sqlite3_close(db);
          return false;
        }
      } else {
        // If the remove was successful, reopen the database.
        int result = sqlite3_open(path.str().c_str(), &db);
        if (result != SQLITE_OK) {
          *error_out = getCurrentErrorMessage();
          return false;
        }
      }

      // Create the schema in a single transaction.
      result = sqlite3_exec(db, "BEGIN EXCLUSIVE;", nullptr, nullptr, &cError);

      // Create the info table.
      if (result == SQLITE_OK) {
        result = sqlite3_exec(
          db, ("CREATE TABLE info ("
               "id INTEGER PRIMARY KEY, "
               "version INTEGER, "
               "client_version INTEGER, "
               "iteration INTEGER);"),
          nullptr, nullptr, &cError);
      }
      if (result == SQLITE_OK) {
        char* query = sqlite3_mprintf(
          "INSERT INTO info VALUES (0, %d, %d, 0);",
          currentSchemaVersion, clientSchemaVersion);
        result = sqlite3_exec(db, query, nullptr, nullptr, &cError);
        sqlite3_free(query);
      }
      if (result == SQLITE_OK) {
        result = sqlite3_exec(
          db, ("CREATE TABLE key_names ("
               "id INTEGER PRIMARY KEY, "
               "key STRING UNIQUE);"),
          nullptr, nullptr, &cError);
      }
      if (result == SQLITE_OK) {
        result = sqlite3_exec(
          db, ("CREATE TABLE rule_results ("
               "id INTEGER PRIMARY KEY, "
               "key_id INTEGER, "
               "value BLOB, "
               "built_at INTEGER, "
               "computed_at INTEGER, "
               "dependencies BLOB, "
               "FOREIGN KEY(key_id) REFERENCES key_names(id));"),
          nullptr, nullptr, &cError);
      }

      // Create the indices on the rule tables.
      if (result == SQLITE_OK) {
        // Create an index to be used for efficiently looking up rule
        // information from a key.
        result = sqlite3_exec(
            db, "CREATE UNIQUE INDEX rule_results_idx ON rule_results (key_id);",
            nullptr, nullptr, &cError);
      }

      // Sync changes to disk.
      if (result == SQLITE_OK) {
        result = sqlite3_exec(db, "END;", nullptr, nullptr, &cError);
      }

      if (result != SQLITE_OK) {
        *error_out = (std::string("unable to initialize database (") + cError
                      + ")");
        sqlite3_free(cError);
        sqlite3_close(db);
        return false;
      }
    }

    // Initialize prepared statements.
    result = sqlite3_prepare_v2(
      db, findKeyIDForKeyStmtSQL,
      -1, &findKeyIDForKeyStmt, nullptr);
    assert(result == SQLITE_OK);

    result = sqlite3_prepare_v2(
      db, findKeyNameForKeyIDStmtSQL,
      -1, &findKeyNameForKeyIDStmt, nullptr);
    assert(result == SQLITE_OK);
    
    result = sqlite3_prepare_v2(
      db, findIDForKeyInRuleResultsStmtSQL,
      -1, &findIDForKeyInRuleResultsStmt, nullptr);
    assert(result == SQLITE_OK);
    
    result = sqlite3_prepare_v2(
      db, insertIntoKeysStmtSQL,
      -1, &insertIntoKeysStmt, nullptr);
    assert(result == SQLITE_OK);
    
    result = sqlite3_prepare_v2(
      db, insertIntoRuleResultsStmtSQL,
      -1, &insertIntoRuleResultsStmt, nullptr);
    assert(result == SQLITE_OK);
    
    result = sqlite3_prepare_v2(
      db, deleteFromKeysStmtSQL,
      -1, &deleteFromKeysStmt, nullptr);
    assert(result == SQLITE_OK);
    
    result = sqlite3_prepare_v2(
      db, deleteFromRuleResultsStmtSQL,
      -1, &deleteFromRuleResultsStmt, nullptr);
    assert(result == SQLITE_OK);
    
    result = sqlite3_prepare_v2(
      db, findRuleResultStmtSQL,
      -1, &findRuleResultStmt, nullptr);
    assert(result == SQLITE_OK);

    return true;
  }

  void close() {
    std::lock_guard<std::mutex> guard(dbMutex);
    assert(db);

    // Destroy prepared statements.
    sqlite3_finalize(findKeyIDForKeyStmt);
    sqlite3_finalize(findKeyNameForKeyIDStmt);
    sqlite3_finalize(findRuleResultStmt);
    sqlite3_finalize(deleteFromKeysStmt);
    sqlite3_finalize(deleteFromRuleResultsStmt);
    sqlite3_finalize(insertIntoKeysStmt);
    sqlite3_finalize(insertIntoRuleResultsStmt);
    sqlite3_finalize(findIDForKeyInRuleResultsStmt);

    sqlite3_close(db);
    db = nullptr;
  }

  /// @name BuildDB API
  /// @{

  virtual uint64_t getCurrentIteration(bool* success_out, std::string *error_out) override {
    std::lock_guard<std::mutex> guard(dbMutex);
    assert(db);

    // Fetch the iteration from the info table.
    sqlite3_stmt* stmt;
    int result;
    result = sqlite3_prepare_v2(
      db, "SELECT iteration FROM info LIMIT 1",
      -1, &stmt, nullptr);
    assert(result == SQLITE_OK);

    result = sqlite3_step(stmt);
    if (result != SQLITE_ROW) {
      *success_out = false;
      *error_out = getCurrentErrorMessage();
      return 0;
    }

    assert(sqlite3_column_count(stmt) == 1);
    uint64_t iteration = sqlite3_column_int64(stmt, 0);

    sqlite3_finalize(stmt);

    *success_out = true;
    return iteration;
  }

  virtual bool setCurrentIteration(uint64_t value, std::string *error_out) override {
    std::lock_guard<std::mutex> guard(dbMutex);
    sqlite3_stmt* stmt;
    int result;
    result = sqlite3_prepare_v2(
      db, "UPDATE info SET iteration = ? WHERE id == 0;",
      -1, &stmt, nullptr);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_int64(stmt, /*index=*/1, value);
    assert(result == SQLITE_OK);

    result = sqlite3_step(stmt);
    if (result != SQLITE_DONE) {
      *error_out = getCurrentErrorMessage();
      return false;
    }

    sqlite3_finalize(stmt);
    return true;
  }

  static constexpr const char *deleteFromKeysStmtSQL = (
      "DELETE FROM key_names WHERE key == ?;");
  sqlite3_stmt* deleteFromKeysStmt = nullptr;
  
  static constexpr const char *findRuleResultStmtSQL = (
      "SELECT id, value, built_at, computed_at, dependencies FROM rule_results "
      "WHERE key_id == ?;");
  sqlite3_stmt* findRuleResultStmt = nullptr;

  virtual bool lookupRuleResult(KeyID keyID, const Rule& rule,
                                Result* result_out,
                                std::string *error_out) override {
    std::lock_guard<std::mutex> guard(dbMutex);
    assert(result_out->builtAt == 0);

    // Fetch the basic rule information.
    int result;

    result = sqlite3_reset(findRuleResultStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_clear_bindings(findRuleResultStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_int64(findRuleResultStmt, /*index=*/1, keyID);
    assert(result == SQLITE_OK);

    // If the rule wasn't found, we are done.
    result = sqlite3_step(findRuleResultStmt);
    if (result == SQLITE_DONE)
      return false;
    if (result != SQLITE_ROW) {
      *error_out = getCurrentErrorMessage();
      return false;
    }

    // Otherwise, read the result contents from the row.
    assert(sqlite3_column_count(findRuleResultStmt) == 5);
    uint64_t ruleID = sqlite3_column_int64(findRuleResultStmt, 0);
    int numValueBytes = sqlite3_column_bytes(findRuleResultStmt, 1);
    result_out->value.resize(numValueBytes);
    memcpy(result_out->value.data(),
           sqlite3_column_blob(findRuleResultStmt, 1),
           numValueBytes);
    result_out->builtAt = sqlite3_column_int64(findRuleResultStmt, 2);
    result_out->computedAt = sqlite3_column_int64(findRuleResultStmt, 3);

    // Extract the dependencies binary blob.
    int numDependencyBytes = sqlite3_column_bytes(findRuleResultStmt, 4);
    const void* dependencyBytes = sqlite3_column_blob(findRuleResultStmt, 4);
    int numDependencies = numDependencyBytes / sizeof(uint64_t);
    if (numDependencyBytes != numDependencies * sizeof(uint64_t)) {
      *error_out = (llvm::Twine("unexpected contents for database result: ") +
                    llvm::Twine((int)ruleID)).str();
      return false;
    }
    result_out->dependencies.resize(numDependencies);
    basic::BinaryDecoder decoder(
        StringRef((const char*)dependencyBytes, numDependencyBytes));
    for (auto i = 0; i != numDependencies; ++i) {
      decoder.read(result_out->dependencies[i]);
    }

    return true;
  }

  static constexpr const char *findIDForKeyInRuleResultsStmtSQL =
    "SELECT id FROM rule_results "
    "WHERE key_id == ? LIMIT 1;";
  sqlite3_stmt* findIDForKeyInRuleResultsStmt = nullptr;

  static constexpr const char *insertIntoRuleResultsStmtSQL =
    "INSERT INTO rule_results VALUES (NULL, ?, ?, ?, ?, ?);";
  sqlite3_stmt* insertIntoRuleResultsStmt = nullptr;

  static constexpr const char *deleteFromRuleResultsStmtSQL =
    "DELETE FROM rule_results WHERE id == ?;";
  sqlite3_stmt* deleteFromRuleResultsStmt = nullptr;

  static constexpr const char *findKeyIDForKeyStmtSQL = (
      "SELECT id FROM key_names "
      "WHERE key == ? LIMIT 1;");
  sqlite3_stmt* findKeyIDForKeyStmt = nullptr;

  static constexpr const char *findKeyNameForKeyIDStmtSQL = (
      "SELECT key FROM key_names "
      "WHERE id == ? LIMIT 1;");
  sqlite3_stmt* findKeyNameForKeyIDStmt = nullptr;

  static constexpr const char *insertIntoKeysStmtSQL =
  "INSERT OR IGNORE INTO key_names(key) VALUES (?);";
  sqlite3_stmt* insertIntoKeysStmt = nullptr;

  /// Inserts a key if not present and always returns keyID
  /// Sometimes key will be inserted for a lookup operation
  /// but that is okay because it'll be added at somepoint anyway
  virtual KeyID getKeyID(const KeyType& key) override {
    std::lock_guard<std::mutex> guard(dbMutex);
    int result;

    // Seach for the key.
    result = sqlite3_reset(findKeyIDForKeyStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_clear_bindings(findKeyIDForKeyStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_text(findKeyIDForKeyStmt, /*index=*/1,
                               key.data(), key.size(),
                               SQLITE_STATIC);
    assert(result == SQLITE_OK);

    result = sqlite3_step(findKeyIDForKeyStmt);
    if (result == SQLITE_ROW) {
      assert(sqlite3_column_count(findKeyIDForKeyStmt) == 1);
      // Found a keyID, return.
      return sqlite3_column_int64(findKeyIDForKeyStmt, 0);
    }

    // Did not find the key, need to insert.
    result = sqlite3_reset(insertIntoKeysStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_clear_bindings(insertIntoKeysStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_text(insertIntoKeysStmt, /*index=*/1,
                               key.data(), key.size(),
                               SQLITE_STATIC);
    assert(result == SQLITE_OK);
    result = sqlite3_step(insertIntoKeysStmt);
    if (result != SQLITE_DONE) {
      // FIXME: We need to support error reporting here, but the engine cannot
      // handle it currently.
      abort();
    }

    return sqlite3_last_insert_rowid(db);
  }

  virtual KeyType getKeyForID(KeyID keyID) override {
    std::lock_guard<std::mutex> guard(dbMutex);
    int result;

    // Seach for the key.
    result = sqlite3_reset(findKeyNameForKeyIDStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_clear_bindings(findKeyNameForKeyIDStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_int64(findKeyNameForKeyIDStmt, /*index=*/1, keyID);
    assert(result == SQLITE_OK);

    result = sqlite3_step(findKeyNameForKeyIDStmt);
    assert(result == SQLITE_ROW);
    assert(sqlite3_column_count(findKeyNameForKeyIDStmt) == 1);

    // Found a keyID, return.
    auto size = sqlite3_column_bytes(findKeyNameForKeyIDStmt, 0);
    auto text = (const char*) sqlite3_column_text(findKeyNameForKeyIDStmt, 0);
    return KeyType(text, size);
  }

  virtual bool setRuleResult(KeyID keyID,
                             const Rule& rule,
                             const Result& ruleResult,
                             std::string *error_out) override {
    std::lock_guard<std::mutex> guard(dbMutex);
    int result;
    uint64_t ruleID = 0;

    // Find the existing rule id, if present.
    //
    // We rely on SQLite3 not using 0 as a valid rule ID.
    result = sqlite3_reset(findIDForKeyInRuleResultsStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_clear_bindings(findIDForKeyInRuleResultsStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_int64(findIDForKeyInRuleResultsStmt, /*index=*/1,
                               keyID);
    assert(result == SQLITE_OK);

    result = sqlite3_step(findIDForKeyInRuleResultsStmt);
    if (result == SQLITE_DONE) {
      ruleID = 0;
    } else if (result == SQLITE_ROW) {
      assert(sqlite3_column_count(findIDForKeyInRuleResultsStmt) == 1);
      ruleID = sqlite3_column_int64(findIDForKeyInRuleResultsStmt, 0);
    } else {
      *error_out = getCurrentErrorMessage();
      return false;
    }

    // If there is an existing entry, delete it first.
    //
    // FIXME: This is inefficient, we should just perform an update.
    if (ruleID != 0) {
      // Delete the rule result.
      result = sqlite3_reset(deleteFromRuleResultsStmt);
      assert(result == SQLITE_OK);
      result = sqlite3_clear_bindings(deleteFromRuleResultsStmt);
      assert(result == SQLITE_OK);
      result = sqlite3_bind_int64(deleteFromRuleResultsStmt, /*index=*/1,
                                  ruleID);
      assert(result == SQLITE_OK);
      result = sqlite3_step(deleteFromRuleResultsStmt);
      if (result != SQLITE_DONE) {
        *error_out = getCurrentErrorMessage();
        return false;
      }
    }

    // Create the encoded dependency list.
    //
    // FIXME: We could save some reallocation by having a templated SmallVector
    // size here.
    basic::BinaryEncoder encoder{};
    for (auto keyID: ruleResult.dependencies) {
      encoder.write(keyID);
    }
    // FIXME: This is doing an unnecessary copy.
    auto encodedDependencies = encoder.contents();
      
    // Insert the actual rule result.
    result = sqlite3_reset(insertIntoRuleResultsStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_clear_bindings(insertIntoRuleResultsStmt);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_int64(insertIntoRuleResultsStmt, /*index=*/1,
                               keyID);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_blob(insertIntoRuleResultsStmt, /*index=*/2,
                               ruleResult.value.data(),
                               ruleResult.value.size(),
                               SQLITE_STATIC);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_int64(insertIntoRuleResultsStmt, /*index=*/3,
                                ruleResult.builtAt);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_int64(insertIntoRuleResultsStmt, /*index=*/4,
                                ruleResult.computedAt);
    assert(result == SQLITE_OK);
    result = sqlite3_bind_blob(insertIntoRuleResultsStmt, /*index=*/5,
                               encodedDependencies.data(),
                               encodedDependencies.size(),
                               SQLITE_STATIC);
    assert(result == SQLITE_OK);
    result = sqlite3_step(insertIntoRuleResultsStmt);
    if (result != SQLITE_DONE) {
      *error_out = getCurrentErrorMessage();
      return false;
    }

    return true;
  }

  virtual bool buildStarted(std::string *error_out) override {
    std::lock_guard<std::mutex> guard(dbMutex);

    // Execute the entire build inside a single transaction.
    //
    // FIXME: We should revist this, as we probably wouldn't want a crash in the
    // build system to totally lose all build results.
    int result = sqlite3_exec(db, "BEGIN EXCLUSIVE;", nullptr, nullptr, nullptr);

    if (result != SQLITE_OK) {
      *error_out = getCurrentErrorMessage();
      return false;
    }

    return true;
  }

  virtual void buildComplete() override {
    std::lock_guard<std::mutex> guard(dbMutex);

    // Sync changes to disk.
    int result = sqlite3_exec(db, "END;", nullptr, nullptr, nullptr);
    assert(result == SQLITE_OK);
    (void)result;
  }

  /// @}
};

}

std::unique_ptr<BuildDB> core::createSQLiteBuildDB(StringRef path,
                                                   uint32_t clientSchemaVersion,
                                                   std::string* error_out) {
  auto db = llvm::make_unique<SQLiteBuildDB>();
  if (!db->open(path, clientSchemaVersion, error_out))
    return nullptr;

  return std::move(db);
}