141 lines
3.2 KiB
JavaScript
141 lines
3.2 KiB
JavaScript
const TOKEN_MAP = {
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EQUALS: "===",
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NOT_EQUALS: "!==",
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LT: "<",
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LTE: "<=",
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MT: ">",
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MTE: ">=",
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CONTAINS: "includes",
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AND: "&&",
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OR: "||",
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}
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const GROUP_PROPERTY = {
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group: {
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type: "string",
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},
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}
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const FIELD_PROPERTY = {
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field: {
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type: "string",
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},
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}
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const SCHEMA_MAP = {
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sum: {
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field: "string",
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value: "number",
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},
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count: {
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field: "string",
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value: "number",
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},
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stats: {
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sum: {
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type: "number",
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},
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min: {
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type: "number",
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},
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max: {
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type: "number",
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},
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count: {
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type: "number",
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},
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sumsqr: {
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type: "number",
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},
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avg: {
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type: "number",
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},
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},
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}
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/**
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* Iterates through the array of filters to create a JS
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* expression that gets used in a CouchDB view.
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* @param {Array} filters - an array of filter objects
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* @returns {String} JS Expression
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*/
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function parseFilterExpression(filters) {
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const expression = []
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for (let filter of filters) {
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if (filter.conjunction) expression.push(TOKEN_MAP[filter.conjunction])
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if (filter.condition === "CONTAINS") {
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expression.push(
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`doc["${filter.key}"].${TOKEN_MAP[filter.condition]}("${filter.value}")`
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)
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} else {
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const value =
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typeof filter.value == "string" ? `"${filter.value}"` : filter.value
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expression.push(
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`doc["${filter.key}"] ${TOKEN_MAP[filter.condition]} ${value}`
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)
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}
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}
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return expression.join(" ")
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}
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/**
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* Returns a CouchDB compliant emit() expression that is used to emit the
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* correct key/value pairs for custom views.
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* @param {String?} field - field to use for calculations, if any
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* @param {String?} groupBy - field to group calculation results on, if any
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*/
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function parseEmitExpression(field, groupBy) {
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return `emit(doc["${groupBy || "_id"}"], doc["${field}"]);`
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}
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/**
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* Return a fully parsed CouchDB compliant view definition
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* that will be stored in the design document in the database.
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*
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* @param {Object} viewDefinition - the JSON definition for a custom view.
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* field: field that calculations will be performed on
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* tableId: tableId of the table this view was created from
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* groupBy: field that calculations will be grouped by. Field must be present for this to be useful
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* filters: Array of filter objects containing predicates that are parsed into a JS expression
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* calculation: an optional calculation to be performed over the view data.
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*/
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function viewTemplate({ field, tableId, groupBy, filters = [], calculation }) {
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const parsedFilters = parseFilterExpression(filters)
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const filterExpression = parsedFilters ? `&& ${parsedFilters}` : ""
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const emitExpression = parseEmitExpression(field, groupBy)
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const reduction = field && calculation ? { reduce: `_${calculation}` } : {}
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let schema = null
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if (calculation) {
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schema = {
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...(groupBy ? GROUP_PROPERTY : FIELD_PROPERTY),
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...SCHEMA_MAP[calculation],
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}
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}
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return {
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meta: {
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field,
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tableId,
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groupBy,
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filters,
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schema,
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calculation,
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},
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map: `function (doc) {
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if (doc.tableId === "${tableId}" ${filterExpression}) {
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${emitExpression}
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}
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}`,
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...reduction,
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}
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}
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module.exports = viewTemplate
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