//! GLSL parsing.
//!
//! This module gives you several functions and types to deal with GLSL parsing, transforming an
//! input source into an AST. The AST is defined in the [`syntax`] module.
//!
//! You want to use the [`Parse`]’s methods to get starting with parsing and pattern match on
//! the resulting [`Result`]. In case of an error, you can inspect the content of the [`ParseError`]
//! object in the `Err` variant.
//!
//! [`Parse`]: crate::parser::Parse
//! [`ParseError`]: crate::parser::ParseError

use nom::error::convert_error;
use nom::Err as NomErr;
use std::fmt;

use crate::parsers::ParserResult;
use crate::syntax;

/// A parse error. It contains a [`String`] giving information on the reason why the parser failed.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ParseError {
  pub info: String,
}

impl std::error::Error for ParseError {}

impl fmt::Display for ParseError {
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
    write!(f, "error: {}", self.info)
  }
}

/// Run a parser `P` on a given `[&str`] input.
pub(crate) fn run_parser<P, T>(source: &str, parser: P) -> Result<T, ParseError>
where
  P: FnOnce(&str) -> ParserResult<T>,
{
  match parser(source) {
    Ok((_, x)) => Ok(x),

    Err(e) => match e {
      NomErr::Incomplete(_) => Err(ParseError {
        info: "incomplete parser".to_owned(),
      }),

      NomErr::Error(err) | NomErr::Failure(err) => {
        let info = convert_error(source, err);
        Err(ParseError { info })
      }
    },
  }
}

/// Class of types that can be parsed.
///
/// This trait exposes the [`Parse::parse`] function that can be used to parse GLSL types.
///
/// The methods from this trait are the standard way to parse data into GLSL ASTs.
pub trait Parse: Sized {
  /// Parse from a string slice.
  fn parse<B>(source: B) -> Result<Self, ParseError>
  where
    B: AsRef<str>;
}

/// Macro to implement Parse for a given type.
macro_rules! impl_parse {
  ($type_name:ty, $parser_name:ident) => {
    impl Parse for $type_name {
      fn parse<B>(source: B) -> Result<Self, ParseError>
      where
        B: AsRef<str>,
      {
        run_parser(source.as_ref(), $crate::parsers::$parser_name)
      }
    }
  };
}

impl_parse!(syntax::Identifier, identifier);
impl_parse!(syntax::TypeSpecifierNonArray, type_specifier_non_array);
impl_parse!(syntax::TypeSpecifier, type_specifier);
impl_parse!(syntax::UnaryOp, unary_op);
impl_parse!(syntax::StructFieldSpecifier, struct_field_specifier);
impl_parse!(syntax::StructSpecifier, struct_specifier);
impl_parse!(syntax::StorageQualifier, storage_qualifier);
impl_parse!(syntax::LayoutQualifier, layout_qualifier);
impl_parse!(syntax::PrecisionQualifier, precision_qualifier);
impl_parse!(syntax::InterpolationQualifier, interpolation_qualifier);
impl_parse!(syntax::TypeQualifier, type_qualifier);
impl_parse!(syntax::TypeQualifierSpec, type_qualifier_spec);
impl_parse!(syntax::FullySpecifiedType, fully_specified_type);
impl_parse!(syntax::ArraySpecifier, array_specifier);
impl_parse!(syntax::Expr, expr);
impl_parse!(syntax::Declaration, declaration);
impl_parse!(syntax::FunctionPrototype, function_prototype);
impl_parse!(syntax::InitDeclaratorList, init_declarator_list);
impl_parse!(syntax::SingleDeclaration, single_declaration);
impl_parse!(syntax::Initializer, initializer);
impl_parse!(syntax::FunIdentifier, function_identifier);
impl_parse!(syntax::AssignmentOp, assignment_op);
impl_parse!(syntax::SimpleStatement, simple_statement);
impl_parse!(syntax::ExprStatement, expr_statement);
impl_parse!(syntax::SelectionStatement, selection_statement);
impl_parse!(syntax::SwitchStatement, switch_statement);
impl_parse!(syntax::CaseLabel, case_label);
impl_parse!(syntax::IterationStatement, iteration_statement);
impl_parse!(syntax::JumpStatement, jump_statement);
impl_parse!(syntax::Condition, condition);
impl_parse!(syntax::Statement, statement);
impl_parse!(syntax::CompoundStatement, compound_statement);
impl_parse!(syntax::FunctionDefinition, function_definition);
impl_parse!(syntax::ExternalDeclaration, external_declaration);
impl_parse!(syntax::TranslationUnit, translation_unit);
impl_parse!(syntax::Preprocessor, preprocessor);
impl_parse!(syntax::PreprocessorVersion, pp_version);
impl_parse!(syntax::PreprocessorVersionProfile, pp_version_profile);
impl_parse!(syntax::PreprocessorExtensionName, pp_extension_name);
impl_parse!(syntax::PreprocessorExtensionBehavior, pp_extension_behavior);
impl_parse!(syntax::PreprocessorExtension, pp_extension);