improve docs, fixes #29 [ci skip]

README.md

@@ -28,7 +28,7 @@ You can now use that for codegen.
 
 Note: problems have been reported while building with JDK 9 on MacOS likely because of [this issue](https://bugs.eclipse.org/bugs/show_bug.cgi?id=534460)
 
-### Code Generation:
+### Code Generation
 
 Use the supplied script `plugin/generate.sh` and point it to the specification file and a configuration file. E.g.:
 
@@ -46,3 +46,90 @@ Typically, you would generate the files into a `src` directory for a package. Th
 The configuration file (`config.json`) can have the following options:
 
 - `packageName`: the Julia package to generate (`SwaggerClient` by default)
+
+## Generated Code Structure
+
+### APIs
+
+Each API set is generated into a file named `api_<apiname>.jl`. It is represented as a `struct` and the APIs under it are generated as methods. An API set can be constructed by providing the
+swagger client instance that it can use for communication.
+
+The required API parameters are generated as regular function arguments. Optional parameters are generated as keyword arguments. Method 
+documentation is generated with description, parameter information and return value.
+
+A client context holds common information to be used across APIs. It also holds a connection to the server and uses that across API calls.
+The client context needs to be passed as the first parameter of all API calls. It can be created as:
+
+```
+Client(root::String;
+    headers::Dict{String,String}=Dict{String,String}(),
+    get_return_type::Function=(default,data)->default,
+    sslconfig=nothing,
+    require_ssl_verification=true)
+```
+
+Where:
+
+- `root`: the root URI where APIs are hosted (should not end with a `/`)
+- `headers`: any additional headers that need to be passed along with all API calls
+- `get_return_type`: optional method that can map a Julia type to a return type other than what is specified in the API specification by looking at the data (this is used only in special cases, for example when models are allowed to be dynamically loaded)
+- `sslconfig`: optional SSL context to use while connecting, e.g. with client certificates needed for validation
+- `require_ssl_verification`: whether to verify the SSL certificate presented by the server (default is to validate)
+
+In case of any errors an instance of `ApiException` is thrown. It has the following fields:
+
+- `status::Int`: HTTP status code
+- `reason::String`: Optional human readable string
+- `resp::HTTP.Response`: The HTTP Response instance associated with this API call
+
+
+An API call involves the following steps:
+- The URL to be invoked is prepared by replacing placeholders in the API URL template with the supplied function parameters.
+- If this is a POST request, serialize the instance of `SwaggerModel` provided as the `body` parameter as a JSON document.
+- Make the HTTP call to the API endpoint and collect the response.
+- Determine the response type / model, invoke the optional user specified mapping function if one was provided.
+- Convert (deserialize) the response data into the return type and return.
+- In case of any errors, throw an instance of `ApiException`
+
+### Models
+
+Each model from the specification is generated into a file named `model_<modelname>.jl`. It is represented as a `mutable struct` that is a subtype of the abstract type `SwaggerModel`. Models have the following methods defined:
+
+- constructor that takes keyword arguments to fill in values for all model properties.
+- [`propertynames`](https://docs.julialang.org/en/v1/base/base/#Base.propertynames)
+- [`hasproperty`](https://docs.julialang.org/en/v1/base/base/#Base.hasproperty)
+- [`getproperty`](https://docs.julialang.org/en/v1/base/base/#Base.getproperty)
+- [`setproperty!`](https://docs.julialang.org/en/v1/base/base/#Base.setproperty!)
+
+In addition to these standard Julia methods, these convenience methods are also generated that help in checking value at a hierarchical path of the model.
+
+- `function haspropertyat(o::T, path...) where {T<:SwaggerModel}`
+- `function getpropertyat(o::T, path...) where {T<:SwaggerModel}`
+
+E.g:
+
+```
+# access o.field.subfield1.subfield2
+if haspropertyat(o, "field", "subfield1", "subfield2")
+    getpropertyat(o, "field", "subfield1", "subfield2")
+end
+
+# access nested array elements, e.g. o.field2.subfield1[10].subfield2
+if haspropertyat(o, "field", "subfield1", 10, "subfield2")
+    getpropertyat(o, "field", "subfield1", 10, "subfield2")
+end
+```
+
+### Validations
+
+Following validations are incorporated into models:
+
+- maximum value: must be a numeric value less than or equal to a specified value
+- minimum value: must be a numeric value greater than or equal to a specified value
+- maximum length: must be a string value of length less than or equal to a specified value
+- minimum length: must be a string value of length greater than or equal to a specified value
+- maximum item count: must be a list value with number of items less than or equal to a specified value
+- minimum item count: must be a list value with number of items greater than or equal to a specified value
+- enum: value must be from a list of allowed values
+
+Validations are imposed in the constructor and `setproperty!` methods of models.