Context

Kind: Interface

Source: src/router/reg-exp-router/node.ts

Part of: Router

Context stores the current variable index while regular-expression route nodes are created. It is passed through route-node insertion so parameter captures can keep consistent positions within generated patterns.

Properties

Diagram

mermaid
graph LR
  Context --> varIndex
  Context --> RouteNodeInsertion
  RouteNodeInsertion --> RegExpPattern

Usage

ts
const context: Context = {
  varIndex: currentVariableIndex,
}

function addRouteVariable(context: Context): number {
  const variableIndex = context.varIndex

  context.varIndex = getNextVariableIndex(variableIndex)

  return variableIndex
}

AI Coding Instructions

• Keep varIndex as a numeric value representing the current route-variable position.
• Pass the same Context object through related route-node insertion calls when variable positions must remain aligned.
• Update varIndex only when adding a route segment that introduces a variable capture.
• Do not reset varIndex during nested node insertion unless starting a separate route-building context.

How it works

Context is an exported TypeScript interface used as mutable insertion state by the regular-expression router’s trie. It contains exactly one numeric field, varIndex. [src/router/reg-exp-router/node.ts:7-9]

• Node.insert() requires a Context argument. [src/router/reg-exp-router/node.ts:51-57]
• Each Trie creates one context with varIndex: 0 and passes that same instance to every root-node insertion. [src/router/reg-exp-router/trie.ts:6-9] [src/router/reg-exp-router/trie.ts:13-17] [src/router/reg-exp-router/trie.ts:54-55]
• When inserting a named dynamic path token, Node.insert() assigns the current context.varIndex to the target node only if that node has no prior variable index, then increments context.varIndex; it also appends the parameter name and assigned index to paramMap. [src/router/reg-exp-router/node.ts:74-77] [src/router/reg-exp-router/node.ts:108-110]
• Wildcard patterns have an empty captured name, so they do not take a varIndex or add a parameter association. [src/router/reg-exp-router/node.ts:64-70] [src/router/reg-exp-router/node.ts:108-110]
• The assigned index is emitted as an @<index> marker while building the trie’s regular-expression string. [src/router/reg-exp-router/node.ts:137-151] Trie.buildRegExp() converts those markers into entries in a parameter replacement map, associating each variable index with a regular-expression capture index. [src/router/reg-exp-router/trie.ts:64-81]

Context itself has no runtime validation or declared errors; its visible side effect is mutation of varIndex during named-parameter insertion. [src/router/reg-exp-router/node.ts:7-9] [src/router/reg-exp-router/node.ts:108-110]