# 1.0 Design Elements {#SDD001}

The rpmget package provides a convenient baseline configuration and
example for managing an arbitrary set of binary rpm packages with
optional support for creating the canonical rpm build tree and pkg
repository.

## SW Dependencies

The primary runtime dependencies are httpx, tqdm, and cerberus,
where cerberus provides the runtime validation for the active user
configuration file. Complete package dependencies are shown in the
figure below:

```{figure} assets/rpmget_dependency_graph.svg
:width: 90 %
:align: center
:alt: rpmget software units

Rpmget Software Units (captured from mermaid to SVG or PNG).
```


<details>
  <summary>rpmget_dependency_graph source</summary>
  rpmget dependency graph showing primary software units.

```mermaid
  graph TB
    subgraph id1[rpmget Dependencies]
      subgraph id2[Python Packages]
        A(rpmget)
        B(httpx)
        C(tqdm)
        D{cerberus}
      end
    end
    A ==> B & C
    A -.-> D
    D -.-> A
```
</details>

## Design decisions

Higher-level API approach (httpx and tqdm) first, minimizing LoC where
possible. Maximize use of the ConfigParser ExtendedInterpolation and
custom validator.

* flexible ConfigParser configuration format
- baseline config file validation via argument
* httpx download client with progress display

Make sure self-test and user-initiated validation always tries to use
provided configuration first, before falling back to the builtin example.


## 1.1 SDD002 {#SDD002}

### Configuration Format

Any INI structured text file acceptable to ConfigParser and within the
following constraints. See the default config for examples.

- Extended Interpolation is enabled, variable style is ${VAR}
- Empty lines in values are NOT supported
- Inline comments are also NOT supported

The current design supports *only* URLs starting with http|https and
ending with '.rpm'.

The downloader should iterate over any URL values that match this
definition.

> `src/rpmget/__init__.py` (line 114)

*Parent links: REQ002*


## 1.2 SDD003 {#SDD003}

### Validation Rules

In addition to the ConfigParser checks, all configurations should be checked
by the validate function using a simple validation schema and URL parsing
based on the following rules. See the default config for an example.

- the [rpmget] section must exist, any others are optional
- the [rpmget] section must contain at least the required keys
  - 'top_dir': the directory where rpms are downloaded
  - 'layout': either 'flat' (single directory) or 'tree'
  - 'pkg_tool': either 'rpm', 'yum', or 'dnf'
- the config must contain at least one valid URL string value ending with '.rpm'

> `src/rpmget/__init__.py` (line 242)

*Parent links: REQ004, REQ006*


## 1.3 SDD004 {#SDD004}

### Initiating Validation Checks

User access to the validation checks should have multiple knobs, eg,
a user-facing CLI argument, the existing self-test cmd, or prior to
actually using a given configuration file.

> `src/rpmget/rpmget.py` (line 46)
> `src/rpmget/rpmget.py` (line 97)

*Parent links: REQ003, REQ005*


## 1.4 SDD005 {#SDD005}

### Downloaded artifact layouts

The software should provide at a minimum two choices how artifacts are
arranged, starting with the following styles:

* flat: all rpm files in a single directory
* tree: the standard rpmbuild tree

The latter rpmbuild layout should also contain the standard `.rpmmacros`
file with default contents.

> `src/rpmget/__init__.py` (line 140)
> `src/rpmget/__init__.py` (line 148)

*Parent links: REQ006, REQ007*


## 1.5 SDD006 {#SDD006}

### Main processing flow

Processing flow in pseudo-code:

- validate_config
- if not `top_dir` then create_layout
- find rpm urls in config
- for each valid url:
  * make subdir from arch suffix
  * download rpm to arch dir