//! Rust API for the [OpenGL API and Extension Registry].
//!
//! # Usage
//! ```
//! use opengl_registry::Registry;
//!
//! let registry = Registry::retrieve().unwrap();
//!
//! for command in registry.commands() {
//!     println!("Command {}", command.prototype().name());
//!     println!("  Return type: {}", command.prototype().return_type());
//!     println!("  Parameters:");
//!
//!     for param in command.parameters() {
//!         println!("  {} {}", param.get_type(), param.name());
//!     }
//! }
//! ```
//!
//! [OpenGL API and Extension Registry]: https://github.com/KhronosGroup/OpenGL-Registry
#![cfg_attr(doc_cfg, feature(doc_cfg))]
#![deny(clippy::all, clippy::pedantic, missing_docs)]

use std::fs::File;
use std::io::Read;

use quick_xml::events::BytesStart;

use crate::command::{Command, Error as CommandError};
use crate::deserialization::buffer_deserializer::BufferDeserializer;
use crate::deserialization::{Deserialize, Deserializer, DeserializerError, IgnoreEnd};

pub mod command;

mod deserialization;

/// XML.
#[cfg(feature = "include-xml")]
const GL_REGISTRY_XML: &[u8] = include_bytes!("../OpenGL-Registry/xml/gl.xml");

const REGISTRY_TAG_NAME: &str = "registry";

/// Representation of the OpenGL registry.
#[derive(Debug, PartialEq, Eq)]
pub struct Registry
{
    commands: Vec<Command>,
}

impl Registry
{
    /// Retrieves the OpenGL registry from a included XML file.
    ///
    /// # Errors
    /// Returns `Err` if parsing fails in any way.
    #[cfg(feature = "include-xml")]
    #[cfg_attr(doc_cfg, doc(cfg(feature = "include-xml")))]
    pub fn retrieve() -> Result<Registry, RegistryError>
    {
        Self::retrieve_from_bytes(GL_REGISTRY_XML)
    }

    /// Retrieves the OpenGL registry from XML bytes.
    ///
    /// # Errors
    /// Returns `Err` if parsing fails in any way.
    pub fn retrieve_from_bytes(xml_bytes: &[u8]) -> Result<Registry, RegistryError>
    {
        let mut deserializer = BufferDeserializer::new(xml_bytes);

        deserializer.skip_to_tag_start(REGISTRY_TAG_NAME)?;

        let registry =
            deserializer.de_tag::<Registry>(REGISTRY_TAG_NAME, IgnoreEnd::Yes)?;

        Ok(registry)
    }

    /// Retrieves the OpenGL registry from a XML file.
    ///
    /// # Errors
    /// Returns `Err` if:
    /// - Parsing fails in any way.
    /// - An I/O error occurs.
    pub fn retrieve_from_file(xml_file: &mut File) -> Result<Registry, RegistryError>
    {
        let mut buf = Vec::new();

        xml_file.read_to_end(&mut buf)?;

        Self::retrieve_from_bytes(&buf)
    }

    /// Creates a new `Registry`.
    ///
    /// # Note
    /// This will **NOT** use anything from the actual OpenGL registry. Use the
    /// [`Registry::retrieve`] method for that.
    pub fn new(commands: impl IntoIterator<Item = Command>) -> Self
    {
        Self {
            commands: commands.into_iter().collect(),
        }
    }

    /// Returns the available commands.
    #[must_use]
    pub fn commands(&self) -> &[Command]
    {
        &self.commands
    }
}

impl Deserialize for Registry
{
    type Error = RegistryError;

    fn deserialize<TDeserializer: Deserializer>(
        _start: &BytesStart,
        deserializer: &mut TDeserializer,
    ) -> Result<Self, Self::Error>
    {
        deserializer.skip_to_tag_start("commands")?;

        let commands =
            deserializer.de_tag_with("commands", IgnoreEnd::No, |_, deserializer| {
                deserializer.de_tag_list::<Command>("command")
            })?;

        Ok(Self { commands })
    }
}

/// [`Registry`] error.
#[derive(Debug, thiserror::Error)]
pub enum RegistryError
{
    /// No 'registry' element was found.
    #[error("No 'registry' element was found")]
    MissingRegistryElement,

    /// No 'commands' element was found.
    #[error("No 'commands' element was found")]
    MissingCommandsElement,

    /// A command is invalid.
    #[error("Invalid command")]
    InvalidCommand(#[from] CommandError),

    /// I/O failed.
    #[error("I/O failed")]
    IOFailed(#[from] std::io::Error),

    /// Deserialization failed.
    #[error("Deserialization failed")]
    DeserializationFailed(#[from] DeserializerError),
}