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89 lines
2.9 KiB
89 lines
2.9 KiB
import {Model} from './Model'
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import {Collection, Maybe} from '../../util'
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import {HasSubtree} from './relation/HasSubtree'
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import {Related} from './relation/decorators'
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/**
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* Model implementation with helpers for querying tree-structured data.
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*
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* This works by using a modified pre-order traversal to number the tree nodes
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* with a left- and right-side numbers. For example:
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*
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* ```txt
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* (1) A (14)
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* |
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* (2) B (9) (10) C (11) (12) D (14)
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* |
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* (3) E (6) (7) G (8)
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* |
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* (4) F (5)
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* ```
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*
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* These numbers are stored, by default, in `left_num` and `right_num` columns.
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* The `subtree()` method returns a `HasSubtree` relation which loads the subtree
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* of a model and recursively nests the nodes.
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*
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* You can use the `children()` helper method to get a collection of the immediate
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* children of this node, which also have the subtree set.
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*
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* To query the model without loading the entire subtree, use the `without()`
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* method on the `ModelBuilder`. For example:
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*
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* ```ts
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* MyModel.query<MyModel>().without('subtree')
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* ```
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*/
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export abstract class TreeModel<T extends TreeModel<T>> extends Model<T> {
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/** The table column where the left tree number is stored. */
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public static readonly leftTreeField = 'left_num'
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/** The table column where the right tree number is stored. */
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public static readonly rightTreeField = 'right_num'
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/**
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* @override to eager-load the subtree by default
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* @protected
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*/
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protected with: (keyof T)[] = ['subtree']
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/** Get the left tree number for this model. */
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public leftTreeNum(): Maybe<number> {
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const ctor = this.constructor as typeof TreeModel
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return this.originalSourceRow?.[ctor.leftTreeField]
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}
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/** Get the right tree number for this model. */
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public rightTreeNum(): Maybe<number> {
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const ctor = this.constructor as typeof TreeModel
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return this.originalSourceRow?.[ctor.rightTreeField]
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}
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/** Returns true if this node has no children. */
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public isLeaf(): boolean {
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const left = this.leftTreeNum()
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const right = this.rightTreeNum()
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return Boolean(left && right && (right - left === 1))
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}
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/** Returns true if the given `node` exists within the subtree of this node. */
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public contains(node: this): boolean {
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const num = node.leftTreeNum()
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const left = this.leftTreeNum()
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const right = this.rightTreeNum()
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return Boolean(num && left && right && (left < num && right > num))
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}
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/** The subtree nodes of this model, recursively nested. */
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@Related()
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public subtree(): HasSubtree<T> {
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const ctor = this.constructor as typeof TreeModel
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return this.make<HasSubtree<T>>(HasSubtree, this, ctor.leftTreeField)
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}
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/** Get the immediate children of this model. */
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public children(): Collection<T> {
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return this.subtree().getValue()
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}
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}
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