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pj
df7da06837
Replace SVG img tag with inline mermaid flowchart showing both native (Maestro sidecar + in-app SDK) and web (Chrome CDP) paths. Update Processes, Transports table, and per-step cycle sections.
82 lines
3.5 KiB
Markdown
82 lines
3.5 KiB
Markdown
---
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title: Architecture
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---
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# Architecture
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```mermaid
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flowchart LR
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subgraph go["sanderling (Go)"]
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B["Bundler / esbuild"] --> V["Verifier / goja + LTL"]
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V <--> R["Runner"]
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R --> D["DeviceDriver"]
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R --> T["Trace writer\nJSONL + PNG"]
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end
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subgraph native["Native platform"]
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SC["Maestro sidecar (JVM)"]
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SDK["in-app SDK"]
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SC -->|UIAutomator / XCTest| SDK
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end
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CH["Chrome (CDP)"]
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D -->|gRPC| SC
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R -->|Unix socket| SDK
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D -->|CDP| CH
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T --> RD[("runs/")]
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RD --> IN["sanderling inspect\nHTTP + SSE"]
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IN --> UI["Web UI (React)"]
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```
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## Processes
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**sanderling (Go).** The top-level binary. Bundles the spec with esbuild, evaluates it in goja, runs the main loop, dispatches actions through the `DeviceDriver` interface, writes the trace.
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**Maestro sidecar (JVM).** A Kotlin process that wraps `maestro-client` and exposes a gRPC surface matching the `DeviceDriver` interface. Handles UI input, screenshots, the system accessibility tree, and OS-level alerts. Native platforms only.
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**In-app SDK.** A Kotlin (or Swift for iOS) library linked into the app under test. Exposes a Unix socket to the runner. Provides pause and resume, view-hierarchy dumps, coverage reads, log capture, and user-registered state extractors. Native platforms only.
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**Chrome (CDP).** For web targets, the Go binary drives Chrome directly over the Chrome DevTools Protocol. No sidecar or in-app SDK is involved.
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## Transports
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| Channel | Platform | Transport | Purpose |
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|---|---|---|---|
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| Go to Maestro sidecar | Native | gRPC (localhost TCP) | UI input, screenshots, system alerts |
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| Go to in-app SDK | Native | Unix domain socket | Pause / resume, hierarchy, coverage, logs, extractors |
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| Go to Chrome | Web | Chrome DevTools Protocol | UI input, screenshots, DOM hierarchy, console logs |
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On native, the transport split exists because only real UI events need to cross process and OS-API boundaries. Introspection is cheap, frequent, and lives on a fast local socket directly to the app. On web, CDP handles both.
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## Inspect UI
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`sanderling inspect` is a separate mode of the same Go binary. It serves an embedded React bundle and reads `runs/` from disk, streaming file-watcher events over SSE so the UI updates as new steps land. It has no connection to any driver; it only consumes the trace artifacts.
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## Per-step cycle
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The heart of the system is:
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```
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pause ─► capture state ─► evaluate properties ─► pick action ─► resume ─► dispatch
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```
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**Native (Android / iOS):**
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1. The runner asks the driver to wait until the UI is idle.
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2. The runner sends `PAUSE` to the SDK over the Unix socket. The SDK freezes the main runloop at a safe point.
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3. The SDK sends back a `STATE` message: view hierarchy, coverage delta, logs since last step, exception list, snapshot values.
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4. The runner feeds state into goja. Extractors re-read; properties re-evaluate; the action generator returns a weighted tree.
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5. The runner writes the trace entry for this step.
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6. The runner picks an action by weight.
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7. The runner sends `RESUME` to the SDK, then dispatches the action through the driver (gRPC to sidecar → Maestro → UIAutomator or XCTest).
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8. Loop.
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**Web (Chrome):**
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Steps 2-3 use CDP to capture the DOM hierarchy and console logs directly; there is no SDK pause/resume. The rest of the cycle is identical.
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The cycle runs hundreds of times per minute. Every step produces one row in `trace.jsonl` and one screenshot.
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