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 # cl-openapi
-Open API Specification for Common Lisp.
+
+OpenAPI 3.0 Specification parser for Common Lisp.
+
+`cl-openapi` parses a JSON-encoded OpenAPI 3.0 document into a tree of
+typed CLOS objects, giving you structured, accessor-based access to every
+field defined by the specification.
+
+## Installation
+
+`cl-openapi` is not yet in the Quicklisp distribution.  Add it to your
+project with [qlot](https://github.com/fukamachi/qlot):
+
+```
+# qlfile
+github cl-openapi cl-sdk/cl-openapi :branch main
+```
+
+Then run `qlot install` and load the system:
+
+```lisp
+(ql:quickload :cl-openapi)
+```
+
+## Usage
+
+### Parsing a document
+
+The single public entry point is `cl-openapi:parse`.  It accepts a JSON
+string, a character stream, or a binary (octet) stream and returns an
+`openapi-document` instance.
+
+```lisp
+;; From a string
+(defvar *doc*
+  (cl-openapi:parse
+   "{\"openapi\":\"3.0.0\",
+     \"info\":{\"title\":\"Pet Store\",\"version\":\"1.0.0\"},
+     \"paths\":{}}"))
+
+;; From a file
+(with-open-file (stream "/path/to/openapi.json")
+  (defvar *doc* (cl-openapi:parse stream)))
+```
+
+### Accessing fields
+
+Every field is exposed through a typed accessor named `<class>-<field>`:
+
+```lisp
+(cl-openapi:openapi-version *doc*)          ; => "3.0.0"
+
+(let ((info (cl-openapi:openapi-info *doc*)))
+  (cl-openapi:info-title info)              ; => "Pet Store"
+  (cl-openapi:info-version info))           ; => "1.0.0"
+
+;; Paths is a hash-table keyed by path string
+(let ((item (gethash "/pets" (cl-openapi:openapi-paths *doc*))))
+  (cl-openapi:operation-id
+    (cl-openapi:path-item-get item)))       ; => "listPets"
+```
+
+Optional fields that are absent from the source document are left **unbound**
+on their slot.  Use `slot-boundp` to test for presence before accessing them.
+
+```lisp
+(let ((info (cl-openapi:openapi-info *doc*)))
+  (when (slot-boundp info 'cl-openapi::description)
+    (cl-openapi:info-description info)))
+```
+
+### `$ref` handling
+
+Wherever the specification permits a Reference Object, the decoded value is
+either the concrete typed object or a `reference` instance whose single
+accessor is `reference-ref` (the raw `$ref` string).
+
+```lisp
+(let ((param (aref (cl-openapi:operation-parameters op) 0)))
+  (if (typep param 'cl-openapi:reference)
+      (cl-openapi:reference-ref param)     ; => "#/components/parameters/Limit"
+      (cl-openapi:parameter-name param)))  ; => "limit"
+```
+
+## API Reference
+
+### Top-level
+
+| Symbol | Description |
+|--------|-------------|
+| `parse input` | Parse a JSON OpenAPI document; returns an `openapi-document`. |
+
+### Classes and accessors
+
+#### `openapi-document`
+`openapi-version` · `openapi-info` · `openapi-servers` · `openapi-paths` ·
+`openapi-components` · `openapi-security` · `openapi-tags` · `openapi-external-docs`
+
+#### `info`
+`info-title` · `info-description` · `info-terms-of-service` · `info-contact` ·
+`info-license` · `info-version`
+
+#### `contact`
+`contact-name` · `contact-url` · `contact-email`
+
+#### `license`
+`license-name` · `license-url`
+
+#### `server`
+`server-url` · `server-description` · `server-variables`
+
+#### `server-variable`
+`server-variable-enum` · `server-variable-default` · `server-variable-description`
+
+#### `path-item`
+`path-item-ref` · `path-item-summary` · `path-item-description` ·
+`path-item-get` · `path-item-put` · `path-item-post` · `path-item-delete` ·
+`path-item-options` · `path-item-head` · `path-item-patch` · `path-item-trace` ·
+`path-item-servers` · `path-item-parameters`
+
+#### `operation`
+`operation-tags` · `operation-summary` · `operation-description` ·
+`operation-external-docs` · `operation-id` · `operation-parameters` ·
+`operation-request-body` · `operation-responses` · `operation-callbacks` ·
+`operation-deprecated` · `operation-security` · `operation-servers`
+
+#### `parameter`
+`parameter-name` · `parameter-in` · `parameter-description` · `parameter-required` ·
+`parameter-deprecated` · `parameter-allow-empty-value` · `parameter-style` ·
+`parameter-explode` · `parameter-allow-reserved` · `parameter-schema` ·
+`parameter-example` · `parameter-examples` · `parameter-content`
+
+#### `request-body`
+`request-body-description` · `request-body-content` · `request-body-required`
+
+#### `response`
+`response-description` · `response-headers` · `response-content` · `response-links`
+
+#### `schema`
+`schema-ref` · `schema-title` · `schema-description` · `schema-type` ·
+`schema-format` · `schema-nullable` · `schema-default` · `schema-example` ·
+`schema-deprecated` · `schema-enum` · `schema-multiple-of` · `schema-maximum` ·
+`schema-exclusive-maximum` · `schema-minimum` · `schema-exclusive-minimum` ·
+`schema-max-length` · `schema-min-length` · `schema-pattern` · `schema-max-items` ·
+`schema-min-items` · `schema-unique-items` · `schema-items` · `schema-max-properties` ·
+`schema-min-properties` · `schema-required` · `schema-properties` ·
+`schema-additional-properties` · `schema-all-of` · `schema-one-of` ·
+`schema-any-of` · `schema-not` · `schema-read-only` · `schema-write-only` ·
+`schema-discriminator` · `schema-xml` · `schema-external-docs`
+
+#### `components`
+`components-schemas` · `components-responses` · `components-parameters` ·
+`components-examples` · `components-request-bodies` · `components-headers` ·
+`components-security-schemes` · `components-links` · `components-callbacks`
+
+#### `security-scheme`
+`security-scheme-type` · `security-scheme-description` · `security-scheme-name` ·
+`security-scheme-in` · `security-scheme-scheme` · `security-scheme-bearer-format` ·
+`security-scheme-flows` · `security-scheme-open-id-connect-url`
+
+#### `oauth-flows`
+`oauth-flows-implicit` · `oauth-flows-password` · `oauth-flows-client-credentials` ·
+`oauth-flows-authorization-code`
+
+#### `oauth-flow`
+`oauth-flow-authorization-url` · `oauth-flow-token-url` · `oauth-flow-refresh-url` ·
+`oauth-flow-scopes`
+
+#### `media-type`
+`media-type-schema` · `media-type-example` · `media-type-examples` · `media-type-encoding`
+
+#### `encoding`
+`encoding-content-type` · `encoding-headers` · `encoding-style` · `encoding-explode` ·
+`encoding-allow-reserved`
+
+#### `header`
+`header-description` · `header-required` · `header-deprecated` ·
+`header-allow-empty-value` · `header-style` · `header-explode` ·
+`header-allow-reserved` · `header-schema` · `header-example` ·
+`header-examples` · `header-content`
+
+#### `example`
+`example-summary` · `example-description` · `example-value` · `example-external-value`
+
+#### `link`
+`link-operation-ref` · `link-operation-id` · `link-parameters` · `link-request-body` ·
+`link-description` · `link-server`
+
+#### `tag`
+`tag-name` · `tag-description` · `tag-external-docs`
+
+#### `external-documentation`
+`external-documentation-description` · `external-documentation-url`
+
+#### `discriminator`
+`discriminator-property-name` · `discriminator-mapping`
+
+#### `xml`
+`xml-name` · `xml-namespace` · `xml-prefix` · `xml-attribute` · `xml-wrapped`
+
+#### `reference`
+`reference-ref`
+
+## License
+
+This is free and unencumbered software released into the public domain.
+See the [Unlicense](LICENSE) for details.