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tinyve.dm.Transaction.js
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tinyve.dm.Transaction.js
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/**
* TinyVE DM Transaction
*
* This is a toy version of ve.dm.Transaction which illustrates the main concepts
*/
/**
* A mapping on tinyve.dm.Document#data that preserves tinyve.dm.Document tree well-formedness.
*
* A transaction consists of a list of operations of two type: retain and replace. To apply
* the list, a conceptual cursor passes through the document's linear data from start to finish
* in a single pass.
*
* A retain operation looks like:
* {
* type: 'retain',
* length: 6
* }
* This means skip the cursor forward 6 steps without changing anything.
*
* A replace operation looks like:
* {
* type: 'replace',
* remove: [ 'f', 'o', 'o' ],
* insert: [ 'b', 'a', 'r' ]
* }
* This means remove the characters 'foo' at the cursor and replace them with 'bar'.
*
* @class
*
* @constructor
* @param {Array} operations Operations preserving tree well-formedness as a whole
*/
tinyve.dm.Transaction = function TinyVeDmTransaction( operations ) {
/**
* @property {Array} operations The operations
*/
this.operations = OO.copy( operations );
};
OO.initClass( tinyve.dm.Transaction );
/**
* Create a reversed version of this transaction, to undo the modifications
*
* @return {tinyve.dm.Transaction} Reversed version of this transaction
*/
tinyve.dm.Transaction.prototype.reversed = function () {
const reversedOperations = this.operations.map( ( op ) => {
// Retain operation: don't change
if ( op.type === 'retain' ) {
return op;
}
// Replace operation: swap insert and remove
return {
type: 'replace',
remove: op.insert,
insert: op.remove
};
} );
return new tinyve.dm.Transaction( reversedOperations );
};

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