//! The main public API for compilation

use std::{
    io::Write,
    path::{Path, PathBuf},
};

use crate::{
    DiagnosticSet, GlyphMap,
    parse::{FileSystemResolver, SourceResolver},
};

use super::{Compilation, FeatureProvider, Opts, VariationInfo, error::CompilerError};

const DEFAULT_N_MESSAGES_TO_PRINT: usize = 100;

/// A builder-style entry point for the compiler.
///
/// This is intended as the principal public API for this crate.
///
/// ```no_run
/// # use fea_rs::{Compiler, compile::{NopFeatureProvider, NopVariationInfo}};
/// # fn make_glyph_map() -> fea_rs::GlyphMap { todo!() }
/// let glyph_map = make_glyph_map();
/// let my_font_bytes = Compiler::<'_, NopFeatureProvider, NopVariationInfo>::new("path/to/features.fea", &glyph_map)
///     .verbose(true)
///     .compile_binary().unwrap();
/// ```
pub struct Compiler<'a, F: FeatureProvider, V: VariationInfo> {
    root_path: PathBuf,
    project_root: Option<PathBuf>,
    glyph_map: &'a GlyphMap,
    // variable fonts only
    var_info: Option<&'a V>,
    feature_writer: Option<&'a F>,
    // this is not in `Opts` because it is specific to the compiler struct;
    // if you're compiling manually you are responsible for handling warnings.
    print_warnings: bool,
    max_n_errors: usize,
    opts: Opts,
    resolver: Option<Box<dyn SourceResolver>>,
}

impl<'a, F: FeatureProvider, V: VariationInfo> Compiler<'a, F, V> {
    /// Configure a new compilation run with a root source and a glyph map.
    ///
    /// In the general case, `root_path` will be a path to a feature file on disk;
    /// however you may compile from memory by passing a custom [`SourceResolver`]
    /// to the [`with_resolver`] method, in which case `root_path` can be any
    /// identifier that your resolver will resolve.
    ///
    /// [`with_resolver`]: Self::with_resolver
    pub fn new(root_path: impl Into<PathBuf>, glyph_map: &'a GlyphMap) -> Self {
        Compiler {
            root_path: root_path.into(),
            glyph_map,
            var_info: None,
            feature_writer: None,
            opts: Default::default(),
            print_warnings: false,
            resolver: Default::default(),
            project_root: Default::default(),
            max_n_errors: DEFAULT_N_MESSAGES_TO_PRINT,
        }
    }

    /// Provide a custom `SourceResolver`, for mapping paths to their contents.
    pub fn with_resolver(mut self, resolver: impl SourceResolver + 'static) -> Self {
        self.resolver = Some(Box::new(resolver));
        self
    }

    /// Provide [`VariationInfo`], necessary when compiling features for a variable font.
    pub fn with_variable_info(mut self, var_info: &'a V) -> Self {
        self.var_info = Some(var_info);
        self
    }

    /// Provide [`FeatureProvider`] to provide additional features during compilation
    pub fn with_feature_writer(mut self, feature_writer: &'a F) -> Self {
        self.feature_writer = Some(feature_writer);
        self
    }

    /// Specify verbosity.
    ///
    /// When verbose is true, we will print all warnings.
    #[deprecated(since = "0.14.1", note = "use print_warnings method instead")]
    pub fn verbose(self, verbose: bool) -> Self {
        self.print_warnings(verbose)
    }

    /// Indicate whether or not warnings should be printed (default is `false`)
    pub fn print_warnings(mut self, warnings: bool) -> Self {
        self.print_warnings = warnings;
        self
    }

    /// Specify an explicit project root.
    ///
    /// This is useful in cases where import resolution is based on an explicit
    /// base directory, such as when dealing with certain source formats.
    pub fn with_project_root(mut self, project_root: impl Into<PathBuf>) -> Self {
        self.project_root = Some(project_root.into());
        self
    }

    /// Specify additional compiler options.
    pub fn with_opts(mut self, opts: Opts) -> Self {
        self.opts = opts;
        self
    }

    /// Parse, validate and compile this source.
    ///
    /// This returns a `Compilation` object that contains all of the features
    /// and lookups generated during compilation. If you would like to go directly
    /// to a binary font, you can use [`compile_binary`] instead.
    ///
    /// [`compile_binary`]: Self::compile_binary
    pub fn compile(self) -> Result<Compilation, CompilerError> {
        let resolver = self.resolver.unwrap_or_else(|| {
            let project_root = self.project_root.unwrap_or_else(|| {
                Path::new(&self.root_path)
                    .parent()
                    .map(PathBuf::from)
                    .unwrap_or_default()
            });
            Box::new(FileSystemResolver::new(project_root))
        });

        let (tree, diagnostics) =
            crate::parse::ParseContext::parse(self.root_path, Some(self.glyph_map), resolver)?
                .generate_parse_tree();
        print_warnings_return_errors(diagnostics, self.print_warnings, self.max_n_errors)
            .map_err(CompilerError::ParseFail)?;
        let diagnostics = super::validate(&tree, self.glyph_map, self.var_info);
        print_warnings_return_errors(diagnostics, self.print_warnings, self.max_n_errors)
            .map_err(CompilerError::ValidationFail)?;
        let mut ctx = super::CompilationCtx::new(
            self.glyph_map,
            tree.source_map(),
            self.var_info,
            self.feature_writer,
            self.opts,
        );
        ctx.compile(&tree.typed_root());

        // we 'take' the errors here because it's easier for us to handle the
        // warnings using our helper method.
        let messages = std::mem::take(&mut ctx.errors);
        let diagnostics = DiagnosticSet::new(messages, &tree, self.max_n_errors);
        print_warnings_return_errors(diagnostics, self.print_warnings, self.max_n_errors)
            .map_err(CompilerError::CompilationFail)?;
        Ok(ctx.build().unwrap().0) // we've taken the errors, so this can't fail
    }

    /// Compile to a binary font.
    pub fn compile_binary(self) -> Result<Vec<u8>, CompilerError> {
        let glyph_map = self.glyph_map;
        Ok(self.compile()?.to_binary(glyph_map)?)
    }
}

fn print_warnings_return_errors(
    mut diagnostics: DiagnosticSet,
    print_warnings: bool,
    max_to_print: usize,
) -> Result<(), DiagnosticSet> {
    diagnostics.set_max_to_print(max_to_print);
    let warnings = diagnostics.split_off_warnings();
    if let Some(warnings) = warnings
        && print_warnings
    {
        // get around a CI check denying eprintln
        let _ = writeln!(std::io::stderr(), "{}", warnings.display());
    }

    if diagnostics.is_empty() {
        Ok(())
    } else {
        Err(diagnostics)
    }
}
