# Writing an app module

A module teaches the binary how to drive one streaming app. It is a Go package, it
is compiled in, and it contains no secrets.

Work through [capture.md](capture.md) first — you need the app's package id,
license URL, manifest host and UI selectors before you can write any of this.

## Anatomy

```text
apps/modules/myapp/
  config.go      Config struct + defaults + flag binding
  myapp.go       init(), the App type, Launch, AutoPlay, capability methods
  steps.go       navigation idioms specific to this app
  catalog.go     optional: resolve channels without a phone
  mpd.go         optional: manifest rewriting
  module.yaml    GITIGNORED - your values
```

Everything is registered from `init()`, and one line in `apps/modules/all/all.go`
links it into the binary.

## 1. Config

Embed `provider.Common` for the fields every module has, then add your own.

```go
package myapp

import (
    "drmdecryption/modcfg"
    "drmdecryption/modules/provider"
)

const Name = "myapp"

type Channel struct {
    Label         string   `yaml:"label"`
    LiveCardIndex int      `yaml:"live_card_index"`
    PlayDesc      []string `yaml:"play_desc"`
}

type Config struct {
    provider.Common `yaml:",inline"`

    // Provider values. Never give these defaults in code.
    APIBase  string             `yaml:"api_base"`
    Channels map[string]Channel `yaml:"channels"`

    Timeouts Timeouts `yaml:"timeouts"`
    UI       UI       `yaml:"ui"`
}

type Timeouts struct {
    // provider.Duration accepts "25s" and bare seconds; time.Duration alone
    // would force raw nanoseconds in YAML.
    LaunchWaitUI provider.Duration `yaml:"launch_wait_ui"`
    Playback     provider.Duration `yaml:"playback"`
}

type UI struct {
    LaunchResourceContains []string `yaml:"launch_resource_contains"`
    LaunchDescContains     []string `yaml:"launch_desc_contains"`
}

func (c Config) withDefaults() Config {
    t := &c.Timeouts
    t.LaunchWaitUI = provider.Duration(t.LaunchWaitUI.D(25 * time.Second))
    t.Playback = provider.Duration(t.Playback.D(45 * time.Second))
    return c
}
```

`provider.Common` gives you `package`, `license_url`, `proxy_bin`, `ca_hash`,
`aliases` and `score`.

### Loading and overrides

```go
var flags struct {
    packageName string
    apiBase     string
}

func loadConfig() (Config, modcfg.Result, error) {
    var cfg Config
    res, err := modcfg.Load(Name, &cfg)      // reads apps/modules/myapp/module.yaml
    if err != nil {
        return cfg, res, err
    }
    cfg.Package = modcfg.Override(Name, "package", flags.packageName, cfg.Package)
    cfg.APIBase = modcfg.Override(Name, "api_base", flags.apiBase, cfg.APIBase)
    return cfg.withDefaults(), res, nil
}
```

`modcfg.Override` applies **flag → environment (`MYAPP_API_BASE`) → file**. A
missing `module.yaml` is not an error: the module must still construct so
`drm modules` can report it as unconfigured.

## 2. The App type

```go
func init() {
    appreg.Register(Name, New)
    appreg.RegisterFlags(bindFlags)
}

func bindFlags(fs *flag.FlagSet) {
    fs.StringVar(&flags.packageName, Name+".package", "", "override "+Name+" package id")
    fs.StringVar(&flags.apiBase, Name+".api-base", "", "override "+Name+" API base")
}

type App struct {
    *provider.Base
    cfg Config
}

func New() (appreg.App, error) {
    cfg, res, err := loadConfig()
    if err != nil {
        return nil, err
    }
    labels := map[string]string{}
    for id, ch := range cfg.Channels {
        labels[id] = ch.Label
    }
    return &App{Base: provider.New(Name, cfg.Common, labels, res), cfg: cfg}, nil
}
```

Flag binding is a separate hook from construction on purpose: flags must be bound
to the config holder *before* any app is built, or overrides would be read too
late.

`provider.Base` supplies `Name`, `Package`, `LicenseURL`, `ProxyBin`, `CAHash`,
`HasChannel`, `Label`, `ChannelIDs`, `CacheDir`, alias-aware `Resolve`, and
`Hints(require…)` preloaded with your `score:` config.

### Required methods

```go
func (a *App) KeyMode() string { return "raw" }   // or "modulardrm"

func (a *App) CaptureHints() capture.Hints {
    return a.Hints("license_url", "mpd")           // fields the MITM must yield
}

func (a *App) MPDRewriter() mpd.Rewriter { return mpd.Passthrough{} }

func (a *App) Channels() []appreg.Channel {
    out := make([]appreg.Channel, 0, len(a.cfg.Channels))
    for _, id := range a.ChannelIDs() {
        out = append(out, appreg.Channel{ID: id, Label: a.Label(id)})
    }
    return out
}
```

`Hints(...)` names the JSON keys that must be present before a capture counts as
complete. Common sets:

| Field | Meaning |
|---|---|
| `mpd` | manifest URL (DASH or HLS — the field name is historical) |
| `license_url` | license endpoint seen on the wire |
| `pssh` | Widevine init data |
| `auth` | Authorization header value |
| `pid` | provider-specific id (e.g. a release/program id) |

Ask only for what the app actually produces. Requiring `pssh` from an HLS app that
puts it in the playlist will hang the capture.

## 3. Launch and AutoPlay

```go
func (a *App) Launch(c *adb.Client) error {
    c.EnsureAwake()
    c.ForceStop(a.Package())
    time.Sleep(400 * time.Millisecond)
    if err := uiflow.MonkeyLaunch(c, a.Package()); err != nil {
        return err
    }
    time.Sleep(time.Duration(a.cfg.Timeouts.LaunchSettle))
    c.DismissShadeIfFocused()
    return uiflow.WaitUI(c, a.CacheDir(), uiflow.Match{
        ResourceContains: a.cfg.UI.LaunchResourceContains,
        DescContains:     a.cfg.UI.LaunchDescContains,
    }, time.Duration(a.cfg.Timeouts.LaunchWaitUI))
}

func (a *App) AutoPlay(c *adb.Client, channel string) error {
    id, err := a.Base.Resolve(channel)
    if err != nil {
        return err
    }
    ch := a.cfg.Channels[id]

    if err := a.openLivePage(c); err != nil {
        return err
    }
    if err := uiflow.TapCard(c, a.CacheDir(), ch.LiveCardIndex,
        time.Duration(a.cfg.Timeouts.Card), a.cfg.Cards); err != nil {
        return err
    }
    return uiflow.WaitPlayback(c, a.CacheDir(), a.Package(), uiflow.PlaybackOpts{
        Timeout:            time.Duration(a.cfg.Timeouts.Playback),
        SoftFail:           true,
        OrResourceContains: a.cfg.UI.PlaybackResourceContains,
    })
}
```

A `Launch` error is logged and tolerated by the capture pipeline, so pick a launch
marker that genuinely exists — otherwise every run silently burns the full timeout
before `AutoPlay` recovers. **Prefer resource ids over descriptions**: ids are
stable and not localized. Dump the real tree to find them:

```bash
adb shell uiautomator dump /sdcard/ui.xml && adb shell cat /sdcard/ui.xml
```

### uiflow

| Function | Use |
|---|---|
| `WaitUI(c, cache, Match, timeout)` | block until a node exists |
| `TapUI(c, cache, Match, timeout)` | wait, then tap its centre |
| `Find(c, cache, Match, timeout)` | get the node for custom handling |
| `WaitPlayback(c, cache, pkg, PlaybackOpts)` | audio session, or a UI fallback signal |
| `Cards(nodes, CardOpts)` | content rows in a dump, top to bottom |
| `WaitCard` / `TapCard` | the nth content row, scrolling if needed |
| `MonkeyLaunch(c, pkg)` | launcher-intent start |
| `CompileRes([]string)` | case-insensitive regexes |

`Match` combines `TextRE`, `DescRE`, `TextContains`, `DescContains`,
`ResourceContains`, plus `Pick` (`largest`/`smallest`/`first`) and `MinArea`.

`WaitPlayback` normally confirms via the audio session. Players that start without
one need `SoftFail: true` plus a UI signal (`OrDescContains`,
`OrResourceContains`) so capture proceeds anyway.

`CardOpts` carries geometry (`MinY`, `MinH`, `MinW`) and denylists (`DescDeny`,
`TextDeny`) so chrome is not mistaken for content. Defaults suit a 1080-wide
phone; put real values in `module.yaml` if your app differs.

## 4. Optional: catalog

Implement `app.Catalog` and `drm catalog --app myapp` starts working.

```go
func (a *App) Resolve(channel string) (session.Stream, error) {
    id, err := a.Base.Resolve(channel)
    // ... hit the provider API, pick a manifest + license URL ...
    return session.Stream{
        Name: Name + "-" + id, App: Name, Channel: id,
        MPD: manifestURL, LicenseURL: licenseURL,
        HeadersJSON: "{}", Rewriter: "none", ManifestType: "hls",
    }, nil
}

func (a *App) EnrichWithKeys(info *session.Stream, python, wvd string) error {
    body, err := brightcove.Get(info.MPD)
    // ... extract PSSH, then wvkey.FetchRawAll ...
}
```

For a nicer `--list`, also implement `app.CatalogLister` returning
`[]appreg.CatalogRow`.

Decode remote config generically. Do not model a provider's JSON field names as Go
struct fields — read into `map[string]any` and let `module.yaml` name the fields:

```yaml
channels:
  main:
    token_field: liveLoggedOutTokenIOI
    stream_id_field: irelandStreamId
```

A renamed upstream field then needs an edit to your values file, not a rebuild.

## 5. Optional: manifest rewriting

Only needed when the captured manifest expires faster than the stream.

```go
func init() {
    mpd.Register(Name, func() mpd.Rewriter { return NewRewriter() })
}

func (r *Rewriter) Name() string { return Name }

func (r *Rewriter) Rewrite(upstreamXML []byte, kidHint string) ([]byte, error) {
    // identify the origin channel from the manifest or the KID, then:
    return mpd.BuildSynthetic(r.cfg.Synthetic, channel, originBase, kid)
}

// Optional: recover the origin when upstream is gone and only the KID remains.
func (r *Rewriter) ResolveKID(kidHex string) (channel, originBase string, ok bool)
func (r *Rewriter) Prime(channel, originBase string)
```

Register a **factory**, not an instance — a rewriter may hold per-stream state.

## 6. Optional: streamd settings

```go
func (a *App) VideoSelect() string  { return "for=best" }
func (a *App) AudioSelect() string  { return "lang=en:for=best" }
func (a *App) RewriterName() string { return Name }    // or "none"
func (a *App) LiveWaitSeconds() int { return 6 }
func (a *App) TSReadyBytes() int64  { return 2 << 20 }
```

Without this, streamd uses neutral defaults. This is what replaced guessing from
app and stream names.

## 7. Link it in

```go
// apps/modules/all/all.go
import (
    _ "drmdecryption/modules/myapp"
    _ "drmdecryption/modules/rte"
    _ "drmdecryption/modules/tg4"
)
```

```bash
go -C apps/cli build -o ../../bin/drm .
./bin/drm modules
```

## 8. Test it

Assert the interfaces at compile time and prove no secrets leaked:

```go
var (
    _ appreg.App            = (*App)(nil)
    _ appreg.Catalog        = (*App)(nil)
    _ appreg.StreamDefaults = (*App)(nil)
)

func TestNoHardcodedCredentials(t *testing.T) {
    cfg := Config{}.withDefaults()
    if cfg.Package != "" || cfg.APIBase != "" {
        t.Fatal("provider values must come from module.yaml")
    }
}
```

`apps/modules/all/all_test.go` already checks every registered module constructs
with no values file present, reports a valid key mode, and — if it declares a
rewriter name — actually registered one.

For anything needing the live service or your local values, use a build tag so the
normal run stays hermetic:

```go
//go:build live
```

```bash
go -C apps/modules test -tags live ./myapp/ -v
```

## Checklist

- [ ] No account id, key, token, video id, hostname or KID in any `.go` file
- [ ] `module.yaml` is gitignored (`git check-ignore -v apps/modules/myapp/module.yaml`)
- [ ] `New()` succeeds with no `module.yaml`
- [ ] Launch marker actually matches — watch for a silent full-timeout wait
- [ ] `CaptureHints` asks only for fields the app really produces
- [ ] `KeyMode` is correct (`raw` for binary challenges, `modulardrm` for JSON)
- [ ] Added to `all/all.go`
- [ ] `drm modules` lists it with the right channel count