| # Optimization Guide Hints |
| |
| This directory contains the implementation of the hints component of the |
| Optimization Guide. Optimization "Hints" are small pieces of metadata about |
| pages that can be fetched from the optimization guide service. This component |
| is responsible for fetching, caching, and managing optimization hints. |
| |
| Most hints can only be fetched from non-incognito profiles that have provided |
| consent for anonymous data collection, but some simple hints are delivered as |
| filters in the optimization guide hints component. |
| |
| ## Overview |
| |
| The core logic resides in `HintsManager`, which is the central class for |
| managing optimization hints. It is responsible for fetching hints from the remote |
| Optimization Guide Service, caching them, and providing Decisions and Metadata. |
| |
| The public-facing API for consumers is the `OptimizationGuideDecider` interface. |
| This interface is implemented by `OptimizationGuideKeyedService` (in |
| `//chrome/browser/optimization_guide`), which acts as a facade. The keyed |
| service owns the `HintsManager` and delegates all decision-making requests to it. |
| |
| Other key classes in this directory include: |
| * `HintsFetcher`: Responsible for fetching hints from the remote service. |
| * `HintCache`: Responsible for caching hints in memory and on disk. |
| * `OptimizationGuideStore`: The persistent store for hints, implemented using |
| a LevelDB database. |
| |
| ## Usage |
| |
| Consumers should obtain an instance of the `OptimizationGuideDecider` interface |
| from the `OptimizationGuideKeyedService` to get Decisions and Metadata. |
| |
| The `HintsManager` (via the `OptimizationGuideKeyedService`) respects user |
| preferences and policies when fetching and providing hints. For example, hint |
| fetches are gated by the checks in the |
| `IsUserPermittedToFetchFromRemoteOptimizationGuide` function, which considers |
| incognito status and user consent for anonymous data collection. |
