# EctoDatabaseFirst

`EctoDatabaseFirst` is a database-first scaffolding library for Ecto projects.
It introspects an existing PostgreSQL schema and generates:

- Ecto schemas
- context modules
- optional snapshot migrations
- a scaffold report with architecture guidance

The focus is not just code generation. The generator also analyzes the schema and
adds practical warnings about naming, missing indexes, oversized tables, and
join-table patterns so the output is easier to maintain.

## Installation

Add the dependency to your `mix.exs`:

```elixir
def deps do
  [
    {:ecto_database_first, "~> 0.1.0"},
    {:postgrex, "~> 0.20"}
  ]
end
```

## Usage

Programmatic API:

```elixir
EctoDatabaseFirst.scaffold(
  otp_app: :my_app,
  base_module: MyApp,
  namespace: "DatabaseFirst",
  repo_module: MyApp.Repo,
  output_path: ".",
  database: [
    hostname: "localhost",
    port: 5432,
    username: "postgres",
    password: "postgres",
    database: "my_app_dev",
    schema: "public"
  ]
)
```

Mix task:

```bash
mix ecto_database_first.scaffold \
  --otp-app my_app \
  --repo-module MyApp.Repo
```

Application config is also supported, which lets the consuming project keep the
scaffold setup in `config/config.exs` and only override specific values from the
CLI when needed:

```elixir
config :my_app, EctoDatabaseFirst,
  base_module: MyApp,
  namespace: "DatabaseFirst",
  repo_module: MyApp.Repo,
  output_path: ".",
  report_path: "scaffold_report.md",
  include_migrations?: true,
  database: [
    hostname: "localhost",
    port: 5432,
    username: "postgres",
    password: "postgres",
    database: "my_app_dev",
    schema: "public"
  ]
```

With that in place, the task can run with just:

```bash
mix ecto_database_first.scaffold
```

If the app already defines an Ecto repo in `config/config.exs`, the scaffold
task can read database credentials directly from the repo configuration. This is
especially helpful for apps that already have:

```elixir
config :my_app, :ecto_repos, [MyApp.Repo]

config :my_app, MyApp.Repo,
  database: "my_app_dev",
  username: "postgres",
  password: "postgres",
  hostname: "localhost",
  port: 5432
```

When multiple repos are configured, pick one explicitly with `--repo-module` or
set `repo_module:` in the `EctoDatabaseFirst` config block.

If you want the command-line options to be saved back into `config/config.exs`
for future runs, use:

```bash
mix ecto_database_first.scaffold --persist-config true
```

Generated output includes code comments and a `scaffold_report.md` file to help
developers understand the design decisions and follow-up improvements.

By default, generated code is placed under a dedicated namespace and folder such
as `MyApp.DatabaseFirst` and `lib/my_app/database_first/...` so it does not
overwrite hand-written schemas or contexts in the main application namespace.

The writer is also conservative by default and refuses to overwrite existing
files unless you pass:

```bash
mix ecto_database_first.scaffold --overwrite true
```

## Design Notes

- Schemas stay focused on fields, associations, and changesets.
- Context modules own `Repo` interaction.
- Tables are grouped into contexts conservatively to avoid fat contexts.
- Snapshot migrations are optional and primarily useful as a baseline export.

## Publishing

This project is structured as a standard Mix library and includes Hex package
metadata in `mix.exs`, so it can be published and installed like other Elixir
libraries.