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+/*
+  2022-09-19
+
+  The author disclaims copyright to this source code.  In place of a
+  legal notice, here is a blessing:
+
+  *   May you do good and not evil.
+  *   May you find forgiveness for yourself and forgive others.
+  *   May you share freely, never taking more than you give.
+
+  ***********************************************************************
+
+  A basic demonstration of the SQLite3 "OO#1" API.
+*/
+'use strict';
+(function(){
+  /**
+     Set up our output channel differently depending
+     on whether we are running in a worker thread or
+     the main (UI) thread.
+  */
+  let logHtml;
+  if(self.window === self /* UI thread */){
+    console.log("Running demo from main UI thread.");
+    logHtml = function(cssClass,...args){
+      const ln = document.createElement('div');
+      if(cssClass) ln.classList.add(cssClass);
+      ln.append(document.createTextNode(args.join(' ')));
+      document.body.append(ln);
+    };
+  }else{ /* Worker thread */
+    console.log("Running demo from Worker thread.");
+    logHtml = function(cssClass,...args){
+      postMessage({
+        type:'log',
+        payload:{cssClass, args}
+      });
+    };
+  }
+  const log = (...args)=>logHtml('',...args);
+  const warn = (...args)=>logHtml('warning',...args);
+  const error = (...args)=>logHtml('error',...args);
+
+  const demo1 = function(sqlite3){
+    const capi = sqlite3.capi/*C-style API*/,
+          oo = sqlite3.oo1/*high-level OO API*/;
+    log("sqlite3 version",capi.sqlite3_libversion(), capi.sqlite3_sourceid());
+    const db = new oo.DB("/mydb.sqlite3",'ct');
+    log("transient db =",db.filename);
+    /**
+       Never(!) rely on garbage collection to clean up DBs and
+       (especially) prepared statements. Always wrap their lifetimes
+       in a try/finally construct, as demonstrated below. By and
+       large, client code can entirely avoid lifetime-related
+       complications of prepared statement objects by using the
+       DB.exec() method for SQL execution.
+    */
+    try {
+      log("Create a table...");
+      db.exec("CREATE TABLE IF NOT EXISTS t(a,b)");
+      //Equivalent:
+      db.exec({
+        sql:"CREATE TABLE IF NOT EXISTS t(a,b)"
+        // ... numerous other options ... 
+      });
+      // SQL can be either a string or a byte array
+      // or an array of strings which get concatenated
+      // together as-is (so be sure to end each statement
+      // with a semicolon).
+
+      log("Insert some data using exec()...");
+      let i;
+      for( i = 20; i <= 25; ++i ){
+        db.exec({
+          sql: "insert into t(a,b) values (?,?)",
+          // bind by parameter index...
+          bind: [i, i*2]
+        });
+        db.exec({
+          sql: "insert into t(a,b) values ($a,$b)",
+          // bind by parameter name...
+          bind: {$a: i * 10, $b: i * 20}
+        });
+      }    
+
+      log("Insert using a prepared statement...");
+      let q = db.prepare([
+        // SQL may be a string or array of strings
+        // (concatenated w/o separators).
+        "insert into t(a,b) ",
+        "values(?,?)"
+      ]);
+      try {
+        for( i = 100; i < 103; ++i ){
+          q.bind( [i, i*2] ).step();
+          q.reset();
+        }
+        // Equivalent...
+        for( i = 103; i <= 105; ++i ){
+          q.bind(1, i).bind(2, i*2).stepReset();
+        }
+      }finally{
+        q.finalize();
+      }
+
+      log("Query data with exec() using rowMode 'array'...");
+      db.exec({
+        sql: "select a from t order by a limit 3",
+        rowMode: 'array', // 'array' (default), 'object', or 'stmt'
+        callback: function(row){
+          log("row ",++this.counter,"=",row);
+        }.bind({counter: 0})
+      });
+
+      log("Query data with exec() using rowMode 'object'...");
+      db.exec({
+        sql: "select a as aa, b as bb from t order by aa limit 3",
+        rowMode: 'object',
+        callback: function(row){
+          log("row ",++this.counter,"=",JSON.stringify(row));
+        }.bind({counter: 0})
+      });
+
+      log("Query data with exec() using rowMode 'stmt'...");
+      db.exec({
+        sql: "select a from t order by a limit 3",
+        rowMode: 'stmt',
+        callback: function(row){
+          log("row ",++this.counter,"get(0) =",row.get(0));
+        }.bind({counter: 0})
+      });
+
+      log("Query data with exec() using rowMode INTEGER (result column index)...");
+      db.exec({
+        sql: "select a, b from t order by a limit 3",
+        rowMode: 1, // === result column 1
+        callback: function(row){
+          log("row ",++this.counter,"b =",row);
+        }.bind({counter: 0})
+      });
+
+      log("Query data with exec() using rowMode $COLNAME (result column name)...");
+      db.exec({
+        sql: "select a a, b from t order by a limit 3",
+        rowMode: '$a',
+        callback: function(value){
+          log("row ",++this.counter,"a =",value);
+        }.bind({counter: 0})
+      });
+
+      log("Query data with exec() without a callback...");
+      let resultRows = [];
+      db.exec({
+        sql: "select a, b from t order by a limit 3",
+        rowMode: 'object',
+        resultRows: resultRows
+      });
+      log("Result rows:",JSON.stringify(resultRows,undefined,2));
+
+      log("Create a scalar UDF...");
+      db.createFunction({
+        name: 'twice',
+        xFunc: function(pCx, arg){ // note the call arg count
+          return arg + arg;
+        }
+      });
+      log("Run scalar UDF and collect result column names...");
+      let columnNames = [];
+      db.exec({
+        sql: "select a, twice(a), twice(''||a) from t order by a desc limit 3",
+        columnNames: columnNames,
+        rowMode: 'stmt',
+        callback: function(row){
+          log("a =",row.get(0), "twice(a) =", row.get(1),
+              "twice(''||a) =",row.get(2));
+        }
+      });
+      log("Result column names:",columnNames);
+
+      try{
+        log("The following use of the twice() UDF will",
+            "fail because of incorrect arg count...");
+        db.exec("select twice(1,2,3)");
+      }catch(e){
+        warn("Got expected exception:",e.message);
+      }
+
+      try {
+        db.transaction( function(D) {
+          D.exec("delete from t");
+          log("In transaction: count(*) from t =",db.selectValue("select count(*) from t"));
+          throw new sqlite3.SQLite3Error("Demonstrating transaction() rollback");
+        });
+      }catch(e){
+        if(e instanceof sqlite3.SQLite3Error){
+          log("Got expected exception from db.transaction():",e.message);
+          log("count(*) from t =",db.selectValue("select count(*) from t"));
+        }else{
+          throw e;
+        }
+      }
+
+      try {
+        db.savepoint( function(D) {
+          D.exec("delete from t");
+          log("In savepoint: count(*) from t =",db.selectValue("select count(*) from t"));
+          D.savepoint(function(DD){
+            const rows = [];
+            DD.exec({
+              sql: ["insert into t(a,b) values(99,100);",
+                    "select count(*) from t"],
+              rowMode: 0,
+              resultRows: rows
+            });
+            log("In nested savepoint. Row count =",rows[0]);
+            throw new sqlite3.SQLite3Error("Demonstrating nested savepoint() rollback");
+          })
+        });
+      }catch(e){
+        if(e instanceof sqlite3.SQLite3Error){
+          log("Got expected exception from nested db.savepoint():",e.message);
+          log("count(*) from t =",db.selectValue("select count(*) from t"));
+        }else{
+          throw e;
+        }
+      }
+    }finally{
+      db.close();
+    }
+
+    log("That's all, folks!");
+
+    /**
+       Some of the features of the OO API not demonstrated above...
+
+       - get change count (total or statement-local, 32- or 64-bit)
+       - get a DB's file name
+    
+       Misc. Stmt features:
+
+       - Various forms of bind() 
+       - clearBindings()
+       - reset()
+       - Various forms of step()
+       - Variants of get() for explicit type treatment/conversion,
+         e.g. getInt(), getFloat(), getBlob(), getJSON()
+       - getColumnName(ndx), getColumnNames()
+       - getParamIndex(name)
+    */
+  }/*demo1()*/;
+
+  log("Loading and initializing sqlite3 module...");
+  if(self.window!==self) /*worker thread*/{
+    /*
+      If sqlite3.js is in a directory other than this script, in order
+      to get sqlite3.js to resolve sqlite3.wasm properly, we have to
+      explicitly tell it where sqlite3.js is being loaded from. We do
+      that by passing the `sqlite3.dir=theDirName` URL argument to
+      _this_ script. That URL argument will be seen by the JS/WASM
+      loader and it will adjust the sqlite3.wasm path accordingly. If
+      sqlite3.js/.wasm are in the same directory as this script then
+      that's not needed.
+
+      URL arguments passed as part of the filename via importScripts()
+      are simply lost, and such scripts see the self.location of
+      _this_ script.
+    */
+    let sqlite3Js = 'sqlite3.js';
+    const urlParams = new URL(self.location.href).searchParams;
+    if(urlParams.has('sqlite3.dir')){
+      sqlite3Js = urlParams.get('sqlite3.dir') + '/' + sqlite3Js;
+    }
+    importScripts(sqlite3Js);
+  }
+  self.sqlite3InitModule({
+    // We can redirect any stdout/stderr from the module
+    // like so...
+    print: log,
+    printErr: error
+  }).then(function(sqlite3){
+    //console.log('sqlite3 =',sqlite3);
+    log("Done initializing. Running demo...");
+    try {
+      demo1(sqlite3);
+    }catch(e){
+      error("Exception:",e.message);
+    }
+  });
+})();