//! <div align="center">
//!   <h1><code>apollo-parser</code></h1>
//!
//!   <p>
//!     <strong>A parser for the GraphQL language.</strong>
//!   </p>
//!   <p>
//!     <a href="https://crates.io/crates/apollo-parser">
//!         <img src="https://img.shields.io/crates/v/apollo-parser.svg?style=flat-square" alt="Crates.io" />
//!     </a>
//!     <a href="https://crates.io/crates/apollo-parser">
//!         <img src="https://img.shields.io/crates/d/apollo-parser.svg?style=flat-square" alt="Download" />
//!     </a>
//!     <a href="https://docs.rs/apollo-parser/">
//!         <img src="https://img.shields.io/static/v1?label=docs&message=apollo-parser&color=blue&style=flat-square" alt="docs.rs docs" />
//!     </a>
//!   </p>
//! </div>
//!
//! ## Features
//! * Typed GraphQL AST as per [October 2021 specification]
//! * Error resilience
//!   * lexing and parsing does not fail or `panic` if a lexical or a syntax error is found
//! * The AST produced is lossless, meaning all ignored tokens like whitespace
//! and commas are kept in the tree
//! * GraphQL lexer
//! * GraphQL parser
//!
//! ## Getting started
//! Add this to your `Cargo.toml` to start using `apollo-parser`:
//! ```toml
//! # Just an example, change to the necessary package version.
//! [dependencies]
//! apollo-parser = "0.2.1"
//! ```
//!
//! Or using [cargo-edit]:
//! ```bash
//! cargo add apollo-parser
//! ```
//!
//! ## Usage
//! `apollo-parser` is built to parse both GraphQL schemas and queries according to the latest [October 2021 specification]. It produces
//! a typed syntax tree that then can be walked, extracting all the necessary
//! information. You can quick start with:
//!
//! ```rust
//! use apollo_parser::Parser;
//!
//! let input = "union SearchResult = Photo | Person | Cat | Dog";
//! let parser = Parser::new(input);
//! let ast = parser.parse();
//! ```
//!
//! `apollo-parser` is built to be error-resilient. This means we don't abort parsing (or lexing) if an error occurs. That means `parser.parse()` will always produce an AST, and it will be accompanied by any errors that are encountered:
//!
//! ```rust
//! use apollo_parser::Parser;
//!
//! let input = "union SearchResult = Photo | Person | Cat | Dog";
//! let parser = Parser::new(input);
//! let ast = parser.parse();
//!
//! // ast.errors() returns an errors slice encountered during lexing and parsing
//! assert_eq!(0, ast.errors().len());
//!
//! // ast.document() get the Document, or root node, of the tree that you can
//! // start iterating on.
//! let doc = ast.document();
//! ```
//!
//! ### Examples
//!
//! Two examples outlined here:
//! * [Get field names in an object]
//! * [Get variables used in a query]
//!
//! The [examples directory] in this repository has a few more useful
//! implementations such as:
//! * [using apollo-rs with miette to display error diagnostics]
//! * [using apollo-rs with annotate_snippets to display error diagnostics]
//! * [checking for unused variables]
//!
//! #### Get field names in an object
//!
//! ```rust
//! use apollo_parser::{ast, Parser};
//!
//! let input = "
//! type ProductDimension {
//!   size: String
//!   weight: Float @tag(name: \"hi from inventory value type field\")
//! }
//! ";
//! let parser = Parser::new(input);
//! let ast = parser.parse();
//! assert_eq!(0, ast.errors().len());
//!
//! let doc = ast.document();
//!
//! for def in doc.definitions() {
//!     if let ast::Definition::ObjectTypeDefinition(object_type) = def {
//!         assert_eq!(object_type.name().unwrap().text(), "ProductDimension");
//!         for field_def in object_type.fields_definition().unwrap().field_definitions() {
//!             println!("{}", field_def.name().unwrap().text()); // size weight
//!         }
//!     }
//! }
//! ```
//!
//! #### Get variables used in a query
//!
//! ```rust
//! use apollo_parser::{ast, Parser};
//!
//! let input = "
//! query GraphQuery($graph_id: ID!, $variant: String) {
//!   service(id: $graph_id) {
//!     schema(tag: $variant) {
//!       document
//!     }
//!   }
//! }
//! ";
//!
//! let parser = Parser::new(input);
//! let ast = parser.parse();
//! assert_eq!(0, ast.errors().len());
//!
//! let doc = ast.document();
//!
//! for def in doc.definitions() {
//!     if let ast::Definition::OperationDefinition(op_def) = def {
//!         assert_eq!(op_def.name().unwrap().text(), "GraphQuery");
//!
//!         let variable_defs = op_def.variable_definitions();
//!         let variables: Vec<String> = variable_defs
//!             .iter()
//!             .map(|v| v.variable_definitions())
//!             .flatten()
//!             .filter_map(|v| Some(v.variable()?.text().to_string()))
//!             .collect();
//!         assert_eq!(
//!             variables.as_slice(),
//!             ["graph_id".to_string(), "variant".to_string()]
//!         );
//!     }
//! }
//! ```
//! ## License
//! Licensed under either of
//!
//! - Apache License, Version 2.0 ([LICENSE-APACHE] or <https://www.apache.org/licenses/LICENSE-2.0>)
//! - MIT license ([LICENSE-MIT] or <https://opensource.org/licenses/MIT>)
//!
//! at your option.
//!
//! [cargo-edit]: https://github.com/killercup/cargo-edit
//! [apollo-rs: spec-compliant GraphQL Tools in Rust]: https://www.apollographql.com/blog/announcement/tooling/apollo-rs-graphql-tools-in-rust/
//! [examples directory]: https://github.com/apollographql/apollo-rs/tree/main/crates/apollo-parser/examples
//! [Get field names in an object]: https://github.com/apollographql/apollo-rs#get-field-names-in-an-object
//! [Get variables used in a query]: https://github.com/apollographql/apollo-rs#get-variables-used-in-a-query
//! [using apollo-rs with miette to display error diagnostics]: https://github.com/apollographql/apollo-rs/blob/a7f616454a53dcb8496725ceac6c63eacddefb2c/crates/apollo-parser/examples/miette.rs
//! [using apollo-rs with annotate_snippets to display error diagnostics]: https://github.com/apollographql/apollo-rs/blob/a7f616454a53dcb8496725ceac6c63eacddefb2c/crates/apollo-parser/examples/annotate_snippet.rs
//! [checking for unused variables]: https://github.com/apollographql/apollo-rs/blob/a7f616454a53dcb8496725ceac6c63eacddefb2c/crates/apollo-parser/examples/unused_vars.rs
//! [October 2021 specification]: https://spec.graphql.org/October2021
//! [LICENSE-APACHE]: https://github.com/apollographql/apollo-rs/blob/main/crates/apollo-parser/LICENSE-APACHE
//! [LICENSE-MIT]:https://github.com/apollographql/apollo-rs/blob/main/crates/apollo-parser/LICENSE-MIT

mod lexer;
#[cfg(test)]
mod tests;

pub mod ast;
mod error;
mod parser;

#[cfg(test)]
pub(crate) use crate::lexer::Lexer;
pub(crate) use crate::lexer::{Token, TokenKind};
pub(crate) use crate::parser::{
    SyntaxElement, SyntaxKind, SyntaxNode, SyntaxNodeChildren, SyntaxToken, TokenText,
};

pub use crate::error::Error;
pub use crate::parser::{Parser, SyntaxTree};