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October 12, 2025 15:58
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Converts a Robot state machine to D2 diagram syntax
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| /** | |
| * Converts a Robot state machine to D2 diagram syntax | |
| * | |
| * Generates a statechart-style visualization with: | |
| * - States, transitions (with event labels), and immediate transitions | |
| * - Guard conditions indicated with [...] notation (e.g., '[...] event') | |
| * - Current state highlighting, final state indicators, invoke state coloring | |
| * - Support for nested machines with recursive rendering | |
| * | |
| * @param {object} machine - A Robot state machine created with createMachine() | |
| * @returns {string} D2 diagram syntax ready to render | |
| * | |
| * @see https://d2lang.com - D2 diagramming language | |
| * @see https://regularhuman.dev - Robot state machine library | |
| * @see https://statecharts.dev - Statechart concepts | |
| */ | |
| export const r2d2 = (machine) => { | |
| const machineLines = (machine, level = 0) => { | |
| const states = Object.entries(machine.states).map(([stateName, state]) => { | |
| const isCurrent = stateName === machine.current; | |
| const lines = [ | |
| ...(isCurrent | |
| ? state.fn || state.machine | |
| ? [`${stateName}.style.stroke: blue`, `${stateName}.style.stroke-width: 3`] | |
| : [`${stateName}.style.fill: lightblue`] | |
| : []), | |
| ...(state.final ? [`${stateName}.style.double-border: true`] : []), | |
| ...(state.fn ? [`${stateName}.style.fill: orange`] : []), | |
| ...(state.machine ? [`${stateName}.style.fill: ${level % 2 ? 'yellow' : 'lightyellow'}`] : []), | |
| ...Array.from(state.transitions ?? []).flatMap(([event, transList]) => | |
| transList.map((transition) => { | |
| const guardPrefix = transition.guards.name !== 'truthy' ? '[...] ' : ''; | |
| return `${stateName} -> ${transition.to}: '${guardPrefix}${event}'`; | |
| }) | |
| ), | |
| ...(state.immediates?.map((immediate) => { | |
| const guardPrefix = immediate.guards.name !== 'truthy' ? '[...] ' : ''; | |
| const label = guardPrefix ? `: '${guardPrefix.trim()}'` : ''; | |
| return `${stateName} -> ${immediate.to}${label}`; | |
| }) ?? []) | |
| ]; | |
| if (state.machine) { | |
| const nested = machineLines(state.machine, level + 1); | |
| return { | |
| lines: [...lines, `${stateName}: {`, ...nested.lines.map((line) => ` ${line}`), `}`], | |
| maxLength: Math.max(stateName.length, nested.maxLength) | |
| }; | |
| } | |
| return { lines, maxLength: stateName.length }; | |
| }); | |
| return { | |
| lines: states.flatMap((state) => state.lines), | |
| maxLength: Math.max(...states.map((state) => state.maxLength)) | |
| }; | |
| }; | |
| const { lines, maxLength } = machineLines(machine, 1); | |
| return [...lines, `*.style.border-radius: 25`, `*.width: ${maxLength * 13}`].join('\n'); | |
| }; |
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