30:T52f,```ts type Policy = Clause[] type Clause = | Select | And | Or | Not | Constraint type Constraint = | GreaterThan | GreaterOrEqualThan | LessThan | LessOrEqualThan | Equal | Like type Term = | Constant | Variable | Reference /** * References use jq like syntax to reference data under * specific path and they start with `.` character. */ type Reference = `.\${string}` /** * Variables are unknowns that engine will substitute * with concrete values as it solves all the constraints. */ type Variable = `?\${string}` /** * Right now we only support scalar constants. */ type Constant = Scalar /** * Supported scalar types */ type Scalar = | null | boolean | number | string | Uint8Array // Binding type Select = [relation: Selector, source:Term, value:Term] type Includes = [relation: "includes", member:Term, group:Term] // Logic type And = [relation: "and", ...Clause[]] type Or = [relation: "or": ...Clause[]] type Not = [relation: "not", Clause] // Constraints type GreaterThan = [relation: '>', Term, Term] type GreaterOrEqualThan = [relation: '>=', Term, Term] type LessThan = [relation: '<', Term, Term] type LessOrEqualThan = [relation: '<=', Term, Term] type Equal = [relation: '==', Term, Term] type Like = [relation: 'like', source:Term, pattern: Term] ```31:T9f2,class Evaluator { static evaluate(policy, context) { return this.and(policy, [new Substitutions().substitute("?", context)]); } static clause([operator, ...operands], frames) { switch (operator) { case "and": return this.and(operands, frames); case "or": return this.or(operands, frames); case "not": return this.not(operands, frames); case "includes": return this.includes(operands, frames); case ">": case ">=": case "<": case "<=": case "==": case "like": return this.constraint(operator, operands, frames); default: return this.select([operator, ...operands], frames); } } static *and(conjuncts, frames) { for (const conjunct of conjuncts) { frames = this.clause(conjunct, frames); } yield* frames; } static *or(disjuncts, frames) { frames = [...frames]; for (const disjunct of disjuncts) { yield* this.clause(disjunct, frames); } } static *not(clause, frames) { for (const frame of frames) { if (isEmpty(this.clause(clause, [frame]))) { yield frame; } } } static *includes([member, group], frames) { for (const bindings of frames) { const reference = resolve(bindings, group); const choice = reference instanceof Reference ? reference.toSome() : reference; yield* unify(member, choice, bindings); } } static *select([selector, subject, value], frames) { for (const bindings of frames) { const target = resolve(bindings, subject); const member = select(target, selector); // TODO: If value is a reference we can not do this yield* unify(member, value, bindings); } } static *constraint(operator, [base, candidate], frames) { const check = this.operators[operator]; for (const bindings of frames) { const left = resolve(bindings, base); const right = resolve(bindings, candidate); if (left == null || right == undefined) { throw new RangeError( `Could not resolve binding ${base == null ? base : candidate}` ); } if (satisfies(check, left, right)) { yield bindings; } } } static operators = { ">": (left, right) => left > right, "<": (left, right) => left < right, ">=": (left, right) => left >= right, "<=": (left, right) => left <= right, "==": (left, right) => left == right, like: (operand, pattern) => compile(pattern).test(operand) }; }32:T53d,/** * * @param {string} source * @param {object} options * @param {boolean} options.ignoreCase * @param {string} options.single * @param {string} options.arbitrary * * @returns */ compile = ( source, { ignoreCase = false, single = "", arbitrary = "*" } = {} ) => { const flags = ignoreCase ? "i" : ""; let pattern = ""; let escaping = false; for (const char of source) { switch (char) { case single: { pattern = escaping ? `${pattern}${char}` : `${pattern}${ANY_CHAR}`; escaping = false; break; } case arbitrary: { pattern = escaping ? `${pattern}${char}` : `${pattern}${ANY_CHAR}*`; escaping = false; break; } case "\\": { pattern = `${pattern}${char}`; escaping = !escaping; break; } case "/": case "*": case "$": case "^": case "+": case ".": case ",": case "(": case ")": case "<": case "=": case "!": case "[": case "]": case "}": case "{": case "|": { pattern = escaping ? `${pattern}${char}` : `${pattern}\\${char}`; escaping = false; break; } default: pattern = `${pattern}${char}`; break; } } return new RegExp(`^${pattern}$`, flags); }33:T151b,class Reference { constructor(members) { this.members = members; } get [Symbol.toStringTag]() { return "Reference"; } toSome() { return this; } satisfies(predicate) { return predicate(this.members[0]); } *unify(other, bindings) { yield* Reference.unify(this.members[0], other, bindings); } select(selector) { return Reference.select(this.members[0], selector); } static *unify(left, right, bindings) { const leftBinding = bindings.resolve(left); const rightBinding = bindings.resolve(right); if (equal(left, right)) { yield bindings; } else if (isVariable(leftBinding)) { yield bindings.substitute(leftBinding, rightBinding); } else if (isVariable(rightBinding)) { yield bindings.substitute(rightBinding, leftBinding); } else if (isUnifier(leftBinding)) { yield leftBinding.unify(rightBinding, bindings); } else if (isUnifier(rightBinding)) { yield rightBinding.unify(leftBinding, bindings); } } static satisfies(predicate, operand, candidate) { if (operand instanceof Reference) { if (candidate instanceof Reference) { return operand.satisfies((left) => candidate.satisfies((right) => predicate(left, right)) ); } else { return operand.satisfies((member) => predicate(member, candidate)); } } else if (candidate instanceof Reference) { return candidate.satisfies((member) => predicate(operand, member)); } else { return predicate(operand, candidate); } } static select(subject, selector) { if (subject instanceof Reference) { return subject.select(selector); } else { const [...members] = Reference.resolve( Reference.tokens(selector), subject ); return members.length === 1 ? new Reference(members) : selector.startsWith("...") ? new Reference.Some(members) : new Reference.Every(members); } } static *resolve([...path], subject) { let current = subject; for (const [offset, segment] of path.entries()) { if (segment === "") { const subpath = path.slice(offset + 1); for (const member of Object.values(current)) { yield* Reference.resolve(subpath, member); } return; } else if (segment.includes(":")) { const [start, end] = segment.split(":"); const startOffset = start === "" ? 0 : parseInt(start); const endOffset = end === "" ? current.length : parseInt(end); current = current.slice(startOffset, endOffset); } else { const index = parseInt(segment); if (!isNaN(index)) { current = current.at(index); } else { current = current[segment]; } } } yield current; } static *tokens(selector) { const { length } = selector; let start = 1; let end = start; let context = ""; while (end < length) { const ch = selector[end]; switch (ch) { case ".": { if (end - start > 0) { yield selector.slice(start, end); } context = ch; end++; start = end; break; } case "[": { if (end - start > 0) { yield selector.slice(start, end); } context = ch; start = end; end++; break; } case "]": { yield selector.slice(start + 1, end); end++; context = ch; start = end; break; } default: { end++; } } } if (end - start > 0) { yield selector.slice(start); } } static Every = class Every extends Reference { constructor(members) { super(); this.members = members; } get [Symbol.toStringTag]() { return "Every"; } toSome() { return new Reference.Some(this.members); } *unify(candidate, bindings) { for (const member of this.members) { // if failed to unify yield no bindings if (isEmpty(Reference.unify(member, candidate, bindings))) { return; } } // if we got here all of the members unify so we yield bindings out yield bindings; } satisfies(predicate) { return this.members.every(predicate); } select(selector) { const members = []; for (const member of this.members) { members.push(Reference.select(member, selector)); } return new Every(members); } }; static Some = class Some extends Reference { constructor(members) { super(); this.members = members; } get [Symbol.toStringTag]() { return "Some"; } select(selector) { const members = []; for (const member of this.members) { members.push(Reference.select(member, selector)); } return new Some(members); } *unify(candidate, bindings) { for (const member of this.members) { yield* Reference.unify(member, candidate, bindings); } } /** * Checks that this reference satisfies predicate. Because this represents * some of the it's members predicate only needs to satisfy some member. */ satisfies(predicate, operand) { return this.members.some(predicate); } }; }34:T41c,function* tokenize(selector) { const { length } = selector; let offset = 0; let column = 0; let context = "."; const segments = []; while (column < length) { const char = selector[column]; if (char === '"' && selector[column - 1] !== "\\") { column++; context = context === '"' ? "" : '"'; continue; } if (context === '"') { column++; continue; } switch (char) { case ".": { if (offset < column) { yield selector.slice(offset, column); } offset = column; column++; break; } case "[": { if (offset < column) { yield selector.slice(offset, column); } offset = column; column++; break; } case "]": { column++; yield selector.slice(offset, column); offset = column; break; } default: { column++; } } } if (offset < column && context != '"') { yield selector.slice(offset, column); } }35:T6dc,parse = (selector) => { const segments = []; let offset = 0; for (const token of tokenize(selector)) { const segment = token.replace(/\s+/g, ""); switch (segment) { case ".": { segments.push(segment); break; } case "[]": { segments.push(segment); break; } default: { if (segment[0] === "[" && segment.at(-1) === "]") { const lookup = segment.slice(1, -1); if (/^\d+$/.test(lookup)) { segments.push(parseInt(lookup, 10)); } else if (lookup[0] === '"' && lookup.at(-1) === '"') { segments.push(lookup.slice(1, -1)); } else if (/^\d*:\d*$/.test(lookup)) { const [left, right] = lookup.split(":"); const start = left !== "" ? parseInt(left, 10) : undefined; const end = right !== "" ? parseInt(right, 10) : undefined; segments.push([start, end]); } else { return new Error( `Selector contains invalid segment ${JSON.stringify( segment )} at ${offset}:${offset + token.length}` ); } } else if (/^\.[a-zA-Z_]*$/.test(segment)) { segments.push(segment.slice(1)); } else { return new Error( `Selector contains invalid segment ${JSON.stringify( segment )} at ${offset}:${offset + token.length}` ); } } } offset += token.length; } if (offset < selector.length) { return { error: new Error( `Selector contains invalid segment ${JSON.stringify( selector.slice(offset) )} with unterminated string` ) }; } return segments; }36:[] 2e:{"title":"UCAN Policy Language","cells":[{"id":0,"value":"# UCAN Policy Language","pinned":false,"hidden":false,"mode":"md"},{"id":36,"value":"$30","pinned":false,"hidden":false,"mode":"md"},{"id":27,"value":"equal = (left, right) => {\n if (left === right) {\n return true;\n } else {\n return false;\n }\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":67,"value":"isVariable = (value) => typeof value === \"string\" && value[0] === \"?\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":641,"value":"isUnifier = (value) => value && typeof value.unify === \"function\"","pinned":true,"hidden":false,"mode":"ojs"},{"id":437,"value":"isReference = (form) => typeof form === \"string\" && form[0] === \".\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":84,"value":"label = (variable) => variable.slice(1)","pinned":false,"hidden":false,"mode":"ojs"},{"id":111,"value":"isEmpty = (iterable) => {\n for (const _ of iterable) {\n return false;\n }\n return true;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":33,"value":"$31","pinned":false,"hidden":false,"mode":"ojs"},{"id":134,"value":"evaluate = (policy, facts) => Evaluator.evaluate(policy, facts)","pinned":true,"hidden":false,"mode":"ojs"},{"id":76,"value":"Rate function takes a clause and gives it a score by which we sort all policy clause. It prioritize selectors and & or logic operators, constraints and then negation so that all bindings get unified before negation occurs.","pinned":false,"hidden":false,"mode":"md"},{"id":65,"value":"rate = ([operator, ...operands]) => {\n let score = 21;\n\n switch (operator) {\n case \"and\":\n score -= 6;\n break;\n case \"or\":\n score -= 5;\n break;\n case \"includes\":\n score -= 4;\n break;\n case \">\":\n case \">=\":\n case \"<\":\n case \"<=\":\n case \"==\":\n case \"like\": {\n score -= 4;\n if (!isVariable(operands[0]) || !isVariable(operands[1])) {\n score += 1;\n }\n break;\n }\n case \"not\":\n score -= 2;\n break;\n default: {\n const [subject, value] = operands;\n if (isVariable(subject)) {\n score -= 7;\n }\n if (isVariable(value)) {\n score -= 6;\n }\n }\n }\n return score;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":80,"value":"class Substitutions {\n substitute(variable, value) {\n return Substitutions.substitute(this, variable, value);\n }\n resolve(variable) {\n return Substitutions.resolve(this, variable);\n }\n\n static resolve(self, term) {\n if (isReference(term)) {\n return Reference.select(self[\"\"], term);\n }\n\n while (isVariable(term)) {\n let next = self[label(term)];\n if (next) {\n term = next;\n } else {\n break;\n }\n }\n\n return term;\n }\n\n static substitute(substitutions, variable, value) {\n const binding = Substitutions.resolve(substitutions, value);\n if (isVariable(binding) && label(binding) === label(variable)) {\n throw new RangeError(\n `Can not substitute ${variable} with ${value} because ${value} is bound to ${variable}`\n );\n }\n\n return Object.assign(new substitutions.constructor(), {\n ...substitutions,\n [label(variable)]: value\n });\n }\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":787,"value":"substitute = Substitutions.substitute","pinned":true,"hidden":false,"mode":"ojs"},{"id":90,"value":"resolve = (substitutions, term) => substitutions.resolve(term)","pinned":false,"hidden":false,"mode":"ojs"},{"id":142,"value":"query = (policy, context) => [...evaluate(policy, context)]","pinned":false,"hidden":false,"mode":"ojs"},{"id":349,"value":"ANY_CHAR = \"[\\\\s\\\\S]\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":347,"value":"$32","pinned":false,"hidden":false,"mode":"ojs"},{"id":377,"value":"select = Reference.select","pinned":false,"hidden":false,"mode":"ojs"},{"id":446,"value":"evaluate(\n [\n [\".messages\", \".\", \"?self\"]\n // [\"in\", \"?email\", \"?to\"],\n // [\"like\", \"?email\", \"*@web.mail\"]\n ],\n {\n messages: [{ to: [\"alice@web.mail\"], message: \"hello\" }]\n }\n)","pinned":true,"hidden":false,"mode":"ojs"},{"id":457,"value":"evaluate([[\"<\", \".x\", \".y\"]], { x: 1, y: 2 })","pinned":true,"hidden":false,"mode":"ojs"},{"id":261,"value":"evaluate(\n [\n [\".messages[].to\", \"?\", \"?to\"],\n [\"includes\", \"?email\", \"?to\"],\n [\"like\", \"?email\", \"*@web.mail\"]\n ],\n {\n messages: [{ to: [\"bob@gmail.com\", \"alice@web.mail\"], message: \"hello\" }]\n }\n)","pinned":true,"hidden":false,"mode":"ojs"},{"id":421,"value":"query(\n [\n [\".mail\", \"?\", \"?mail\"],\n [\"includes\", \"?message\", \"?mail\"]\n ],\n {\n mail: [\n { to: [\"alice@web.mail\"], message: \"hello\" },\n { to: [\"bob@gmail.com\"], message: \"hello\" }\n ]\n }\n)","pinned":true,"hidden":false,"mode":"ojs"},{"id":432,"value":"query(\n [\n [\".mail\", \".\", \"?mail\"],\n [\".[]\", \"?mail\", \"?message\"]\n ],\n {\n mail: [\n { to: [\"alice@web.mail\"], message: \"hello\" },\n { to: [\"bob@gmail.com\"], message: \"hello\" }\n ]\n }\n)","pinned":true,"hidden":false,"mode":"ojs"},{"id":358,"value":"Test Dataset","pinned":false,"hidden":false,"mode":"md"},{"id":359,"value":"data = ({\n mail: [\n { to: [\"alice@web.mail\", \"malory@web.mail\"], body: \"hello alice\" },\n {\n to: [\"bob@gmail.com\", \"alice@web.mail\"],\n body: \"hi bob\"\n }\n ]\n})","pinned":true,"hidden":false,"mode":"ojs"},{"id":365,"value":"Every message MUST must have some recipient that matches *@web.mail.","pinned":false,"hidden":false,"mode":"md"},{"id":366,"value":"evaluate(\n [\n [\".mail\", \".\", \"?msgs\"]\n // [\"of\", \"?msg\", \"?msgs\"]\n // [\".to\", \"?msg\", \"?to\"],\n // [\"in\", \"?email\", \"?to\"],\n // [\"like\", \"?email\", \"*@web.mail\"]\n ],\n data\n)","pinned":true,"hidden":false,"mode":"ojs"},{"id":509,"value":"Every email in `to` must contain at least `*@fission.codes` or `*@protocol.ai`","pinned":false,"hidden":false,"mode":"md"},{"id":501,"value":"query(\n [\n // [\"includes\", \"?to\", \".to[]\"],\n // we unpack each requirement\n // [\".required[]\", \".\", \"?required\"]\n [\"includes\", \"?required\", \".required[]\"],\n [\".to[]\", \".\", \"?to\"],\n // check that every single one matches requirement\n [\"like\", \"?to\", \"?required\"]\n ],\n {\n to: [\n \"alice@fission.codes\",\n \"bob@protocol.ai\",\n \"finance@fission.codes\",\n \"fraud@fission.codes\"\n // should not match if removed\n // \"bob@gmail.com\"\n ],\n // I don't support array literals yet so we'll stick them here\n required: [\"*@fission.codes\", \"*@protocol.ai\"]\n }\n)","pinned":true,"hidden":false,"mode":"ojs"},{"id":634,"value":"query([[\"includes\", \"?x\", [1, 2, 4]]], {})","pinned":true,"hidden":false,"mode":"ojs"},{"id":780,"value":"unify = Reference.unify","pinned":true,"hidden":false,"mode":"ojs"},{"id":782,"value":"satisfies = Reference.satisfies","pinned":true,"hidden":false,"mode":"ojs"},{"id":553,"value":"$33","pinned":false,"hidden":false,"mode":"ojs"},{"id":839,"value":"$34","pinned":true,"hidden":false,"mode":"ojs"},{"id":873,"value":"$35","pinned":false,"hidden":false,"mode":"ojs"}],"files":"$W36","stdlib":"1","titling":"auto"}