# Architecture

SubMiner uses a service-oriented Electron architecture with a composition-oriented main process and a modular renderer process.

## Goals

- Keep behavior stable while reducing coupling.
- Prefer small, single-purpose units that can be tested in isolation.
- Keep `main.ts` focused on wiring and state ownership, not implementation detail.
- Follow Unix-style composability:
  - each service does one job
  - services compose through explicit inputs/outputs
  - orchestration is separate from implementation

## Project Structure

```text
src/
  main.ts                  # Entry point — delegates to src/main/ composition modules
  preload.ts               # Electron preload bridge
  types.ts                 # Shared type definitions
  main/                    # Composition root modules (extracted from main.ts)
    app-lifecycle.ts       # Electron lifecycle event registration
    cli-runtime.ts         # CLI command handling and dispatch
    dependencies.ts        # Shared dependency builders for IPC/runtime
    ipc-mpv-command.ts     # MPV command composition helpers
    ipc-runtime.ts         # IPC channel registration and handlers
    overlay-runtime.ts      # Overlay window/modal selection and state
    overlay-shortcuts-runtime.ts # Overlay keyboard shortcut handling
    startup.ts              # Startup bootstrap flow (argv/env processing)
    startup-lifecycle.ts    # App-ready initialization sequence
    state.ts                # Application runtime state container
    subsync-runtime.ts      # Subsync command orchestration
  core/
    services/              # ~60 focused service modules (see below)
    utils/                 # Pure helpers and coercion/config utilities
  cli/                     # CLI parsing and help output
  config/                  # Config schema, defaults, validation, template generation
  renderer/                # Overlay renderer (modularized UI/runtime)
  window-trackers/         # Backend-specific tracker implementations (Hyprland, Sway, X11, macOS)
  jimaku/                  # Jimaku API integration helpers
  subsync/                 # Subtitle sync (alass/ffsubsync) helpers
  subtitle/                # Subtitle processing utilities
  tokenizers/              # Tokenizer implementations
  token-mergers/           # Token merge strategies
  translators/             # AI translation providers
```

### Service Layer (`src/core/services/`)

- **Startup** — `startup-service`, `app-lifecycle-service`, `app-ready-service`
- **Overlay** — `overlay-manager-service`, `overlay-window-service`, `overlay-visibility-service`, `overlay-bridge-service`, `overlay-runtime-init-service`, `overlay-content-measurement-service`
- **Shortcuts** — `shortcut-service`, `overlay-shortcut-service`, `overlay-shortcut-handler`, `shortcut-fallback-service`, `numeric-shortcut-service`, `numeric-shortcut-session-service`
- **MPV** — `mpv-service`, `mpv-control-service`, `mpv-render-metrics-service`, `mpv-transport`, `mpv-protocol`, `mpv-state`, `mpv-properties`
- **IPC** — `ipc-service`, `ipc-command-service`, `runtime-options-ipc-service`
- **Mining** — `mining-service`, `field-grouping-service`, `field-grouping-overlay-service`, `anki-jimaku-service`, `anki-jimaku-ipc-service`
- **Subtitles** — `subtitle-ws-service`, `subtitle-position-service`, `secondary-subtitle-service`, `tokenizer-service`
- **Integrations** — `jimaku-service`, `subsync-service`, `subsync-runner-service`, `texthooker-service`, `yomitan-extension-loader-service`, `yomitan-settings-service`
- **Config** — `runtime-config-service`, `cli-command-service`

### Renderer Layer (`src/renderer/`)

The overlay renderer is split by concern so `renderer.ts` stays focused on bootstrapping, IPC wiring, and module composition.

```text
src/renderer/
  renderer.ts              # Entrypoint/orchestration only
  context.ts               # Shared runtime context contract
  state.ts                 # Centralized renderer mutable state
  subtitle-render.ts       # Primary/secondary subtitle rendering + style application
  positioning.ts           # Visible/invisible positioning + mpv metrics layout
  handlers/
    keyboard.ts            # Keybindings, chord handling, modal key routing
    mouse.ts               # Hover/drag behavior, selection + observer wiring
  modals/
    jimaku.ts              # Jimaku modal flow
    kiku.ts                # Kiku field-grouping modal flow
    runtime-options.ts     # Runtime options modal flow
    subsync.ts             # Manual subsync modal flow
  utils/
    dom.ts                 # Required DOM lookups + typed handles
    platform.ts            # Layer/platform capability detection
```

## Flow Diagram

```mermaid
flowchart TD
  classDef root fill:#c6a0f6,stroke:#24273a,color:#24273a,stroke-width:2px
  classDef comp fill:#b7bdf8,stroke:#24273a,color:#24273a,stroke-width:1.5px
  classDef svc fill:#8aadf4,stroke:#24273a,color:#24273a,stroke-width:1.5px
  classDef ext fill:#a6da95,stroke:#24273a,color:#24273a,stroke-width:1.5px

  Main["src/main.ts"]:::root

  subgraph Composition["Composition Modules"]
    Startup["Startup & Lifecycle"]:::comp
    IpcCli["IPC & CLI Wiring"]:::comp
    Overlay["Overlay & Shortcuts"]:::comp
    Subsync["Subsync"]:::comp
  end

  subgraph Services["Domain Services"]
    OverlaySvc["Overlay Services"]:::svc
    MpvSvc["MPV Stack"]:::svc
    MiningSvc["Mining & Subtitles"]:::svc
    ShortcutIpc["Shortcuts & IPC"]:::svc
  end

  subgraph External["External Boundaries"]
    Config["Config & CLI"]:::ext
    Trackers["Window Trackers"]:::ext
    Integrations["Jimaku & Subsync"]:::ext
  end

  Main --> Startup
  Main --> IpcCli
  Main --> Overlay
  Main --> Subsync

  Startup --> OverlaySvc
  IpcCli --> ShortcutIpc
  Overlay --> OverlaySvc
  Overlay --> MpvSvc
  Subsync --> Integrations

  OverlaySvc --> Trackers
  MpvSvc --> MiningSvc
  ShortcutIpc --> Config

  style Composition fill:#363a4f,stroke:#494d64,color:#cad3f5
  style Services fill:#363a4f,stroke:#494d64,color:#cad3f5
  style External fill:#363a4f,stroke:#494d64,color:#cad3f5
```

## Composition Pattern

Most runtime code follows a dependency-injection pattern:

1. Define a service interface in `src/core/services/*`.
2. Keep core logic in pure or side-effect-bounded functions.
3. Build runtime deps in `src/main/` composition modules; extract an adapter/helper only when it adds meaningful behavior or reuse.
4. Call the service from lifecycle/command wiring points.

The composition root (`src/main.ts`) delegates to focused modules in `src/main/`:
- `startup.ts` — argv/env processing and bootstrap flow
- `app-lifecycle.ts` — Electron lifecycle event registration
- `startup-lifecycle.ts` — app-ready initialization sequence
- `state.ts` — centralized application runtime state container
- `ipc-runtime.ts` — IPC channel registration and handler wiring
- `cli-runtime.ts` — CLI command parsing and dispatch
- `overlay-runtime.ts` — overlay window selection and modal state management
- `subsync-runtime.ts` — subsync command orchestration

This keeps side effects explicit and makes behavior easy to unit-test with fakes.

## Lifecycle Model

- **Startup:**
  - `src/main/startup.ts` (`startup-service`) handles initial argv/env/backend setup and decides generate-config flow vs app lifecycle start.
  - `src/main/app-lifecycle.ts` (`app-lifecycle-service`) handles Electron single-instance + lifecycle event registration.
  - `src/main/startup-lifecycle.ts` performs ready-time initialization (config load, websocket policy, tokenizer/tracker setup, overlay auto-init decisions).
- **Runtime:**
  - CLI/shortcut/IPC events map to service calls through `src/main/cli-runtime.ts`, `src/main/ipc-runtime.ts`, and `src/main/overlay-runtime.ts`.
  - Overlay and MPV state sync through dedicated services.
  - Runtime options and mining flows are coordinated via service boundaries.
- **Shutdown:**
  - `app-lifecycle-service` registers cleanup hooks (`will-quit`) while teardown behavior stays delegated to focused services from `src/main/*` composition modules.

```mermaid
flowchart TD
  classDef phase fill:#b7bdf8,stroke:#24273a,color:#24273a,stroke-width:1.5px
  classDef decision fill:#f5a97f,stroke:#24273a,color:#24273a,stroke-width:1.5px
  classDef runtime fill:#8aadf4,stroke:#24273a,color:#24273a,stroke-width:1.5px
  classDef shutdown fill:#a6da95,stroke:#24273a,color:#24273a,stroke-width:1.5px

  Args["CLI args / env"]:::phase --> Startup["src/main/startup.ts"]:::phase

  Startup --> Decision{"generate-config?"}:::decision

  Decision -->|yes| WriteConfig["Write config + exit"]:::phase
  Decision -->|no| AppLifecycle["src/main/app-lifecycle.ts"]:::phase

  AppLifecycle --> Ready["src/main/startup-lifecycle.ts\nConfig · WebSocket · Tracker · Tokenizer · State"]:::phase

  Ready --> Runtime["Runtime Modules\nipc · cli · overlay · subsync"]:::runtime

  Runtime --> Overlay["Overlay & Mining"]:::runtime
  Runtime --> Subtitle["Subtitle Processing"]:::runtime
  Runtime --> SubsyncInt["Subsync & Jimaku"]:::runtime

  Runtime --> WillQuit["Electron will-quit"]:::shutdown
  WillQuit --> Cleanup["Service Teardown"]:::shutdown
```

## Why This Design

- **Smaller blast radius:** changing one feature usually touches one service.
- **Better testability:** most behavior can be tested without Electron windows/mpv.
- **Better reviewability:** PRs can be scoped to one subsystem.
- **Backward compatibility:** CLI flags and IPC channels can remain stable while internals evolve.
- **Extracted composition root:** TASK-27 refactored `main.ts` into focused modules under `src/main/`, isolating startup, lifecycle, IPC, CLI, and domain-specific runtime wiring.
- **Split MPV service:** TASK-27.4 separated `mpv-service.ts` into transport (`mpv-transport.ts`), protocol (`mpv-protocol.ts`), state (`mpv-state.ts`), and properties (`mpv-properties.ts`) layers for improved maintainability.

## Extension Rules

- Add behavior to an existing service in `src/core/services/*` or create a new focused module in `src/main/` for composition-level logic — not as ad-hoc logic in `main.ts`.
- Keep service APIs explicit and narrowly scoped.
- Prefer additive changes that preserve existing CLI flags and IPC channel behavior.
- Add/update unit tests for each service extraction or behavior change.
- For cross-cutting changes, extract-first then refactor internals after parity is verified.
- When adding new IPC channels or CLI commands, register them in the appropriate `src/main/` module (`ipc-runtime.ts` for IPC, `cli-runtime.ts` for CLI).