OF-DL/AGENTS.md

# AGENTS.md

Note: Keep AGENTS.md updated as project structure, key services, or workflows change.

This repo is **OF DL** (also known as OF-DL), a C# console app that downloads media from a user's OnlyFans account(s).
This document is for AI agents helping developers modify the project. It focuses on architecture, data flow, and the
most important change points.

**Quick Flow**

1. `Program.Main` builds DI, loads `config.conf`, and runs the interactive flow.
2. `StartupService.CheckVersionAsync` checks the latest release tag (`OFDLV*`) from `git.ofdl.tools` when not in DEBUG.
3. `StartupService.ValidateEnvironmentAsync` validates OS, FFmpeg, `rules.json`, and Widevine device files.
4. `AuthService` loads `auth.json` or opens a browser login (PuppeteerSharp) and persists auth data.
5. `ApiService` signs every API request with dynamic rules and the current auth.
6. `DownloadOrchestrationService` selects creators, prepares folders/DBs, and calls `DownloadService` per media type.
7. `DownloadService` downloads media, handles DRM, and records metadata in SQLite.

**Project Layout**

- `OF DL/Program.cs` orchestrates startup, config/auth loading, and the interactive flow (CLI entrypoint).
- `OF DL/CLI/` contains Spectre.Console UI helpers and progress reporting (CLI-only).
- `OF DL.Core/Services/` contains application services (API, auth, download, config, DB, startup, logging, filenames).
- `OF DL.Core/Models/` holds configuration, auth, DTOs, entities, and mapping helpers.
- `OF DL.Core/Widevine/` implements Widevine CDM handling and key derivation.
- `OF DL.Core/Helpers/`, `OF DL.Core/Utils/`, `OF DL.Core/Crypto/`, `OF DL.Core/Enumerations/` contain shared core logic.
- `docs/` and `mkdocs.yml` define the documentation site.
- `site/` is generated MkDocs output and should not be edited by hand.
- `docker/` contains container entrypoint and supervisor configuration.

**Key Services**

- `ApiService` (`OF DL.Core/Services/ApiService.cs`) builds signed headers, performs HTTP requests, and maps DTOs to
  entities. It also handles DRM-related calls like MPD/PSSH extraction and license requests.
- `AuthService` (`OF DL.Core/Services/AuthService.cs`) loads `auth.json` or performs browser-based login with PuppeteerSharp,
  then persists auth. It also normalizes cookies.
- `ConfigService` (`OF DL.Core/Services/ConfigService.cs`) loads `config.conf` (HOCON), migrates legacy `config.json`, and
  updates global settings (logging, text sanitization).
- `DownloadService` (`OF DL.Core/Services/DownloadService.cs`) downloads all media (images, video, audio) and handles DRM
  video decryption and FFmpeg execution.
- `DownloadOrchestrationService` (`OF DL.Core/Services/DownloadOrchestrationService.cs`) coordinates user selection,
  subscription lists, per-user folder prep, and per-media-type download execution.
- `DBService` (`OF DL.Core/Services/DBService.cs`) manages SQLite metadata DBs for downloaded media and a `users.db` index.
- `StartupService` (`OF DL.Core/Services/StartupService.cs`) validates FFmpeg, rules.json, Widevine device files, and
  performs release version checks.
- `LoggingService` (`OF DL.Core/Services/LoggingService.cs`) writes logs to `logs/OFDL.txt` and updates log level based on
  config.
- `FileNameService` (`OF DL.Core/Services/FileNameService.cs`) formats filenames using the custom format rules from config.

**Models: DTOs vs Entities**

- DTOs live under `OF DL.Core/Models/Dtos/` and mirror API response JSON.
- Entities live under `OF DL.Core/Models/Entities/` and represent the internal domain used by download logic.
- Mappers in `OF DL.Core/Models/Mappers/` convert DTOs into entities to isolate API changes from downstream logic.

**Configuration**

- Primary config file is `config.conf` (HOCON). `ConfigService` migrates legacy `config.json` if found and creates a
  default `config.conf` if missing.
- `Config` lives in `OF DL.Core/Models/Config.cs` and is populated by `ConfigService.LoadConfigFromFileAsync`.
- `ConfigService.UpdateConfig` is the central place where runtime config changes are applied (logging level and text
  sanitization).
- CLI flag `--non-interactive` forces non-interactive mode; `ConfigService.IsCliNonInteractive` and
  `Config.NonInteractiveMode` both gate prompts.
- FFmpeg path is read from `config.conf`, `auth.json`, or auto-detected from PATH/current directory.

**Runtime Files (relative to the working directory)**

- `config.conf`, `auth.json`, and `rules.json` are loaded from the current working directory.
- `cdm/` (Widevine device files), `chrome-data/` (Puppeteer profile), and `logs/` are created under the working
  directory.
- `users.db` is stored at the working directory root.

**Authentication Flow**

- Auth data is stored in `auth.json` using the `Auth` model in `OF DL.Core/Models/Auth.cs`.
- `AuthService.LoadFromBrowserAsync` launches Chrome via PuppeteerSharp, waits for login, then extracts `auth_id` and
  `sess` cookies, `bcTokenSha` from localStorage (used as `X_BC`), and `USER_AGENT` from the browser.
- `AuthService.ValidateCookieString` rewrites the cookie string so it contains only `auth_id` and `sess` and ensures a
  trailing `;`.
- `AuthService` uses `chrome-data/` as its user data directory; `Logout` deletes `chrome-data` and `auth.json`.

Environment variables used by auth:

- `OFDL_DOCKER=true` toggles Docker-specific instructions and browser flags.
- `OFDL_PUPPETEER_EXECUTABLE_PATH` overrides the Chromium path for PuppeteerSharp.

**Dynamic Rules and Signature Headers**

- All OnlyFans API requests use dynamic headers from `ApiService.GetDynamicHeaders`.
- Dynamic rules are fetched from `https://git.ofdl.tools/sim0n00ps/dynamic-rules/raw/branch/main/rules.json` with
  fallback to local `rules.json` in the current working directory. The repo ships `OF DL/rules.json` as the default
  rules file.
- Cache durations: 15 minutes for remote rules, 5 minutes for local rules.
- `DynamicRules` shape is defined in `OF DL.Core/Models/DynamicRules.cs` and includes `app-token`, `static_param`, `prefix`,
  `suffix`, `checksum_constant`, and `checksum_indexes`.

Signature algorithm in `GetDynamicHeaders`:

- `input = "{static_param}\n{timestamp_ms}\n{path+query}\n{user_id}"`
- `hash = SHA1(input)` lower-case hex string
- `checksum = sum(hashString[index] char values) + checksum_constant`
- `sign = "{prefix}:{hash}:{checksum_hex}:{suffix}"`

Headers included in signed requests:

- `app-token`, `sign`, `time`, `user-id`, `user-agent`, `x-bc`, `cookie`.

**Widevine CDM and DRM Decryption**

- Runtime Widevine device files are expected at `cdm/devices/chrome_1610/device_client_id_blob` and
  `cdm/devices/chrome_1610/device_private_key` (relative to the working directory). Paths are defined in
  `OF DL.Core/Widevine/Constants.cs` and validated in `StartupService`.

DRM flow is primarily in `DownloadService.GetDecryptionInfo` and `ApiService` DRM helpers:

- `ApiService.GetDRMMPDPSSH` downloads the MPD manifest and extracts the `cenc:pssh` value.
- `ApiService.GetDRMMPDLastModified` uses CloudFront signed cookies and returns MPD `Last-Modified`.
- `DownloadService.GetDecryptionInfo` builds DRM headers (via `GetDynamicHeaders`) and hits the license endpoint.

Two decryption paths exist:

- If CDM device files exist, `ApiService.GetDecryptionKeyCDM` uses `Widevine/CDMApi`.
- If missing, `ApiService.GetDecryptionKeyOFDL` calls `https://ofdl.tools/WV` as a fallback.

`DownloadService.DownloadDrmMedia` runs FFmpeg with `-cenc_decryption_key`, CloudFront cookies, and auth
cookies/user-agent. Output is written to `{filename}_source.mp4`, then moved and recorded in SQLite.

**Download Paths, Data, and Logs**

- Default download root is `__user_data__/sites/OnlyFans/{username}` when `DownloadPath` is blank. This is computed in
  `DownloadOrchestrationService.ResolveDownloadPath`.
- Each creator folder gets a `Metadata/user_data.db` (SQLite) managed by `DBService`.
- A global `users.db` in the working directory tracks subscribed creators and user IDs.
- Logs are written to `logs/OFDL.txt` (rolling daily); FFmpeg report files are also written under `logs/` when debug
  logging is enabled.

**Docs (MkDocs)**

- Docs source lives under `docs/` and configuration is in `mkdocs.yml`.
- Build the site with `mkdocs build --clean` (outputs to `site/`).
- Preview locally with `mkdocs serve`.

**CI/CD (Gitea Workflows)**

- `/.gitea/workflows/publish-docs.yml` builds and deploys docs on tag pushes matching `OFDLV*` and on manual dispatch.
- `/.gitea/workflows/publish-docker.yml` builds multi-arch Docker images on `OFDLV*` tags and pushes to the Gitea
  registry.
- `/.gitea/workflows/publish-release.yml` publishes Windows and Linux builds on `OFDLV*` tags and creates a draft
  release.

**Docker Image**

- Built via `/.gitea/workflows/publish-docker.yml` on tag pushes `OFDLV*`.
- Image tags: `git.ofdl.tools/sim0n00ps/of-dl:latest` and `git.ofdl.tools/sim0n00ps/of-dl:{version}`.
- Build args include `VERSION` (tag name with `OFDLV` stripped).
- Platforms: `linux/amd64` and `linux/arm64`.
- Runtime uses `/config` as the working directory and `/data` for downloads; `docker/entrypoint.sh` seeds
  `/config/config.conf` and `/config/rules.json` from `/default-config`.

**Release Checklist**

1. Update docs under `docs/` and verify locally with `mkdocs build --clean` or `mkdocs serve`.
2. Tag the release as `OFDLV{version}` and push the tag.
3. Verify the draft release artifact and publish the release in Gitea.

**Coding Style (from .editorconfig)**

- Indentation: 4 spaces by default, 2 spaces for XML/YAML/project files. No tabs.
- Line endings: LF for `*.sh`, CRLF for `*.cmd`/`*.bat`.
- C# braces on new lines (`csharp_new_line_before_open_brace = all`).
- Prefer predefined types (`int`, `string`) and avoid `var` except when type is apparent.
- `using` directives go outside the namespace and `System` namespaces are sorted first.
- Private/internal fields use `_camelCase`; private/internal static fields use `s_` prefix.
- `const` fields should be PascalCase.
- Prefer braces for control blocks and expression-bodied members (silent preferences).

**Where to Look First**

- `OF DL/Program.cs` for the execution path and menu flow.
- `OF DL.Core/Services/ApiService.cs` for OF API calls and header signing.
- `OF DL.Core/Services/DownloadService.cs` for downloads and DRM handling.
- `OF DL.Core/Services/DownloadOrchestrationService.cs` for creator selection and flow control.
- `OF DL.Core/Widevine/` for CDM key generation and license parsing.
- `OF DL.Core/Models/Config.cs` and `OF DL.Core/Services/ConfigService.cs` for config shape and parsing.
- `OF DL.Core/Services/AuthService.cs` for user-facing authentication behavior and browser login flow.
- `docs/` for public documentation; update docs whenever user-facing behavior or configuration changes.

Documentation updates for common changes:

- Config option added/removed/changed in `Config` or `config.conf`: update `docs/config/all-configuration-options.md` (
  full spec), `docs/config/configuration.md` (organized list), and `docs/config/custom-filename-formats.md` if filename
  tokens or formats are affected.
- Authentication flow changes (browser login, legacy methods, required fields): update `docs/config/auth.md`.
- CLI/menu flow or download workflow changes: update `docs/running-the-program.md`.
- Docker runtime or container flags/paths change: update `docs/installation/docker.md`.