// sqlite3.uc - SQLite3 FFI wrapper example
   // Demonstrates FFI with complex structs, callbacks, and memory management
   
   import * as ffi from 'ffi';
   
   // Constants
   const SQLITE_OK = 0;
   const SQLITE_ROW = 100;
   const SQLITE_DONE = 101;
  const SQLITE_ERROR = 1;
  
  // ============================================================================
  // run - Complete SQLite3 FFI Demo
  //
  // Demonstrates FFI usage with SQLite3, covering: dynamic library loading,
  // struct and pointer types, prepared statements, parameter binding, result
  // column extraction, and error handling. Shows how persistent ctype buffers
  // are required for string arguments since native ucode string memory may not
  // remain valid across native calls.
  //
  // Steps performed:
  //   1. Load sqlite3 library from system paths (tries x86_64, i386, then PATH)
  //   2. Query library version info (libversion, libversion_number)
  //   3. Open an in-memory database using sqlite3_open()
  //   4. Create a users table with CREATE TABLE via sqlite3_exec()
  //   5. Insert two rows using prepared statements with parameter binding
  //      - Uses ffi.string() to create persistent char[N] ctype buffers, then
  //        passes .ptr() to bind_text() so the memory outlives the call
  //   6. Execute SELECT with step/column extraction via prepared statements
  //   7. Demonstrate error handling with an invalid query via sqlite3_exec()
  //   8. Report error details using sqlite3_errmsg() and sqlite3_errcode()
  //   9. Close the database via sqlite3_close()
  //
  // Usage:
  //   ucode examples/ffi/sqlite3.uc
  //
  // Dependencies: libsqlite3 installed on the system
  // ============================================================================
  
  function run() {
      print("=== SQLite3 FFI Demo ===\n");
  
      // Load sqlite3 library with cdefs
      print("Loading sqlite3 library...\n");
      let sqlite3lib = null;
  
      let cdefs = `
          typedef struct sqlite3 sqlite3;
          typedef struct sqlite3_stmt sqlite3_stmt;
          typedef void sqlite3_destructor_type;
  
          const char *sqlite3_libversion(void);
          int sqlite3_libversion_number(void);
          int sqlite3_open(const char *, void **);
          int sqlite3_close(void *);
          int sqlite3_exec(void *, const char *, int, int, int);
          int sqlite3_prepare_v2(void *, const char *, int, void **, const char **);
          int sqlite3_reset(void *);
          int sqlite3_finalize(void *);
          int sqlite3_step(void *);
          int sqlite3_bind_text(void *, int, const char *, int, int);
          int sqlite3_bind_int(void *, int, int);
          const unsigned char *sqlite3_column_text(void *, int);
          int sqlite3_column_int(void *, int);
          double sqlite3_column_double(void *, int);
          const char *sqlite3_errmsg(void *);
          int sqlite3_errcode(void *);
          int sqlite3_changes(void *);
      `;
  
      try {
          sqlite3lib = ffi.dlopen('/usr/lib/x86_64-linux-gnu/libsqlite3.so.0', false, cdefs);
      } catch (e) {
          try {
              sqlite3lib = ffi.dlopen('/usr/lib/i386-linux-gnu/libsqlite3.so.0', false, cdefs);
          } catch (e2) {
              try {
                  sqlite3lib = ffi.dlopen('sqlite3', false, cdefs);
              } catch (e3) {
                  sqlite3lib = null;
              }
          }
      }
  
      if (!sqlite3lib) {
          print("Could not load sqlite3 library. Install libsqlite3-dev to run this demo.\n");
          print("Skipping demo.\n");
          return;
      }
  
      print("Library loaded successfully.\n\n");
  
      // 1. Version info
      let version_ptr = sqlite3lib.sqlite3_libversion();
      let version = ffi.string(version_ptr);
      print("SQLite version: ", version, "\n");
      print("Version number: ", sqlite3lib.sqlite3_libversion_number(), "\n\n");
  
      // 2. Create in-memory database
     print("Creating in-memory database...\n");
     let db = ffi.ctype('void *', null);
     let rc = sqlite3lib.sqlite3_open(':memory:', db.ptr());
     if (rc !== SQLITE_OK)
         die("Failed to open database: error " + rc);
 
     // 3. Create schema
     print("Creating tables...\n");
     let createSQL = "CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT NOT NULL, email TEXT)";
     rc = sqlite3lib.sqlite3_exec(db, createSQL, 0, 0, 0);
     if (rc !== SQLITE_OK)
         die("Failed to create users table");
 
     // 4. Insert data
     print("Inserting users...\n");
     let insertSQL = "INSERT INTO users (name, email) VALUES (?, ?)";
     let stmtPtr = ffi.ctype('void *', null);
     rc = sqlite3lib.sqlite3_prepare_v2(db, insertSQL, -1, stmtPtr.ptr(), null);
     if (rc !== SQLITE_OK)
         die("Failed to prepare insert");
     let insertStmt = stmtPtr;
 
     // Insert Alice
     let aliceName = ffi.string('Alice');
     let aliceEmail = ffi.string('alice@example.com');
     sqlite3lib.sqlite3_bind_text(insertStmt, 1, aliceName.ptr(), -1, 0);
     sqlite3lib.sqlite3_bind_text(insertStmt, 2, aliceEmail.ptr(), -1, 0);
     rc = sqlite3lib.sqlite3_step(insertStmt);
     if (rc !== SQLITE_DONE)
         die("Insert Alice failed");
 
     // Insert Bob
     sqlite3lib.sqlite3_reset(insertStmt);
     let bobName = ffi.string('Bob');
     let bobEmail = ffi.string('bob@example.com');
     sqlite3lib.sqlite3_bind_text(insertStmt, 1, bobName.ptr(), -1, 0);
     sqlite3lib.sqlite3_bind_text(insertStmt, 2, bobEmail.ptr(), -1, 0);
     rc = sqlite3lib.sqlite3_step(insertStmt);
     if (rc !== SQLITE_DONE)
         die("Insert Bob failed");
 
     sqlite3lib.sqlite3_finalize(insertStmt);
     print("Inserted ", sqlite3lib.sqlite3_changes(db), " rows\n\n");
 
     // 5. Query data
     print("Querying users...\n");
     let selectSQL = "SELECT id, name, email FROM users ORDER BY id";
     rc = sqlite3lib.sqlite3_prepare_v2(db, selectSQL, -1, stmtPtr.ptr(), null);
     let selectStmt = stmtPtr;
     while (sqlite3lib.sqlite3_step(selectStmt) === SQLITE_ROW) {
         let id = sqlite3lib.sqlite3_column_int(selectStmt, 0);
         let name_ptr = sqlite3lib.sqlite3_column_text(selectStmt, 1);
         let email_ptr = sqlite3lib.sqlite3_column_text(selectStmt, 2);
         let name = ffi.string(name_ptr);
         let email = ffi.string(email_ptr);
         print("  User: ", id, " - ", name, " <", email, ">\n");
     }
     sqlite3lib.sqlite3_finalize(selectStmt);
 
     // 6. Error handling demo
     print("\n=== Error Handling Demo ===\n");
     rc = sqlite3lib.sqlite3_exec(db, "SELECT * FROM nonexistent_table", 0, 0, 0);
     if (rc !== SQLITE_OK) {
         let errmsg_ptr = sqlite3lib.sqlite3_errmsg(db);
         let errmsg = ffi.string(errmsg_ptr);
         print("Caught error: ", errmsg, "\n");
         print("Error code: ", sqlite3lib.sqlite3_errcode(db), "\n");
     }
 
     // Clean up
     sqlite3lib.sqlite3_close(db);
 
     print("\n=== Demo Complete ===\n");
 }
 
 // Run demo
 run();

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