//! Implementation of the Schema-to-Rust compiler; this is the core of the
//! [preserves-schema-rs][] program.
//!
//! See the [documentation for preserves-schema-rs][preserves-schema-rs] for examples of how to
//! use the compiler programmatically from a `build.rs` script, but very briefly, use
//! [preserves-schemac](https://preserves.dev/doc/preserves-schemac.html) to generate a
//! metaschema instance `*.prb` file, and then put something like this in `build.rs`:
//!
//! ```rust,ignore
//! use preserves_schema::compiler::*;
//!
//! const PATH_TO_PRB_FILE: &'static str = "your-metaschema-instance-file.prb";
//!
//! fn main() -> Result<(), std::io::Error> {
//!     let buildroot = std::path::PathBuf::from(std::env::var_os("OUT_DIR").unwrap());
//!
//!     let mut gen_dir = buildroot.clone();
//!     gen_dir.push("src/schemas");
//!     let mut c = CompilerConfig::new("crate::schemas".to_owned());
//!
//!     let inputs = expand_inputs(&vec![PATH_TO_PRB_FILE.to_owned()])?;
//!     c.load_schemas_and_bundles(&inputs, &vec![])?;
//!     compile(&c, &mut CodeCollector::files(gen_dir))
//! }
//! ```
//!
//! plus something like this in your `lib.rs` or main program:
//!
//! ```rust,ignore
//! pub mod schemas {
//!     include!(concat!(env!("OUT_DIR"), "/src/schemas/mod.rs"));
//! }
//! ```
//!
//! [preserves-schema-rs]: https://preserves.dev/doc/preserves-schema-rs.html

pub mod context;
pub mod cycles;
pub mod names;
pub mod parsers;
pub mod readers;
pub mod types;
pub mod unparsers;

use crate::compiler::context::*;
use crate::compiler::types::Purpose;
use crate::gen::schema;
use crate::gen::schema::*;
use crate::gen::Language;
use crate::syntax::block::constructors::*;
use crate::syntax::block::{Formatter, Item};
use crate::*;

use glob::glob;
use preserves::value::BinarySource;
use preserves::value::BytesBinarySource;
use preserves::value::Map;
use preserves::value::Reader;
use preserves::value::Set;

use std::fs::DirBuilder;
use std::fs::File;
use std::io;
use std::io::Read;
use std::io::Write;
use std::path::PathBuf;

/// Names a Schema module within a (collection of) Schema bundle(s).
pub type ModulePath = Vec<String>;

/// Implement this trait to extend the compiler with custom code generation support. The main
/// code generators are also implemented as plugins.
///
/// For an example of its use outside the core compiler, see [`build.rs` for the `syndicate-rs` project](https://git.syndicate-lang.org/syndicate-lang/syndicate-rs/src/commit/60e6c6badfcbcbccc902994f4f32db6048f60d1f/syndicate/build.rs).
pub trait Plugin: std::fmt::Debug {
    /// Use `_module_ctxt` to emit code at a per-module level.
    fn generate_module(&self, _module_ctxt: &mut ModuleContext) {}

    /// Use `module_ctxt` to emit code at a per-Schema-[Definition] level.
    fn generate_definition(
        &self,
        module_ctxt: &mut ModuleContext,
        definition_name: &str,
        definition: &Definition,
    );
}

pub struct LanguageTypes {
    pub fallback: Option<Box<dyn Fn(&str) -> Set<String>>>,
    pub definitions: Map<String, Box<dyn Fn(&str) -> Set<String>>>,
}

impl std::fmt::Debug for LanguageTypes {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
        f.debug_struct("LanguageTypes")
            .field("fallback", &self.fallback.as_ref().map(|f| f("_")))
            .field(
                "definitions",
                &self
                    .definitions
                    .iter()
                    .map(|(k, f)| (k.clone(), f("_")))
                    .collect::<Map<String, Set<String>>>(),
            )
            .finish()
    }
}

#[derive(Debug)]
pub struct ExternalModule {
    pub path: ModulePath,
    pub rust_namespace: String,
    pub rust_language_types: LanguageTypes,
}

impl ExternalModule {
    pub fn new(path: ModulePath, rust_namespace: &str) -> Self {
        ExternalModule {
            path,
            rust_namespace: rust_namespace.to_owned(),
            rust_language_types: LanguageTypes {
                fallback: None,
                definitions: Map::new(),
            },
        }
    }

    pub fn set_fallback_language_types<F: 'static + Fn(&str) -> Set<String>>(
        mut self,
        f: F,
    ) -> Self {
        self.rust_language_types.fallback = Some(Box::new(f));
        self
    }

    pub fn set_definition_language_types<F: 'static + Fn(&str) -> Set<String>>(
        mut self,
        d: &str,
        f: F,
    ) -> Self {
        if self
            .rust_language_types
            .definitions
            .insert(d.to_owned(), Box::new(f))
            .is_some()
        {
            panic!(
                "Duplicate language types definition installed: {:?} {:?}",
                &self.path, d
            );
        }
        self
    }
}

/// Used to collect output from the compiler.
pub enum CodeModuleCollector<'a> {
    /// Default file-based code emitter.
    Files {
        /// Where output Rust code files will be placed.
        output_dir: PathBuf,
    },
    Custom {
        /// Used to collect the various produced source files.
        /// Useful for when compiling in e.g. proc_macro context.
        collect_output: &'a mut dyn FnMut(Option<&ModulePath>, &str) -> io::Result<()>,
    },
}

/// Used to configure and collect output from the compiler.
pub struct CodeCollector<'a> {
    pub emit_mod_declarations: bool,
    pub collect_module: CodeModuleCollector<'a>,
}

/// Main entry point to the compiler.
#[derive(Debug)]
pub struct CompilerConfig {
    /// All known Schema modules, indexed by [ModulePath] and annotated with a [Purpose].
    pub bundle: Map<ModulePath, (Schema, Purpose)>,
    /// Fully-qualified Rust module prefix to use for each generated module.
    pub fully_qualified_module_prefix: String,
    /// Rust module path to the [preserves_schema::support][crate::support] module.
    pub support_crate: String,
    /// External modules for cross-referencing.
    pub external_modules: Map<ModulePath, ExternalModule>,
    /// Plugins active in this compiler instance.
    pub plugins: Vec<Box<dyn Plugin>>,
    /// If true, a directive is emitted in each module instructing
    /// [rustfmt](https://github.com/rust-lang/rustfmt) to ignore it.
    pub rustfmt_skip: bool,
}

/// Loads a [Schema] or [Bundle] from path `i` into `bundle` for the given `purpose`.
///
/// If `i` holds a [Schema], then the file stem of `i` is used as the module name when placing
/// the schema in `bundle`.
pub fn load_schema_or_bundle_with_purpose(
    bundle: &mut Map<ModulePath, (Schema, Purpose)>,
    i: &PathBuf,
    purpose: Purpose,
) -> io::Result<()> {
    let mut inserted = Map::<ModulePath, Schema>::new();
    load_schema_or_bundle(&mut inserted, i)?;
    for (k, v) in inserted.into_iter() {
        bundle.insert(k, (v, purpose));
    }
    Ok(())
}

/// Loads a [Schema] or [Bundle] from raw binary encoded value `input` into `bundle` for the
/// given `purpose`.
///
/// If `input` corresponds to a [Schema], then `prefix` is used as its module name; otherwise,
/// it's a [Bundle], and `prefix` is ignored.
pub fn load_schema_or_bundle_bin_with_purpose(
    bundle: &mut Map<ModulePath, (Schema, Purpose)>,
    prefix: &str,
    input: &[u8],
    purpose: Purpose,
) -> io::Result<()> {
    let mut inserted = Map::<ModulePath, Schema>::new();
    load_schema_or_bundle_bin(&mut inserted, prefix, input)?;
    for (k, v) in inserted.into_iter() {
        bundle.insert(k, (v, purpose));
    }
    Ok(())
}

fn bundle_prefix(i: &PathBuf) -> io::Result<&str> {
    i.file_stem()
        .ok_or_else(|| {
            io::Error::new(
                io::ErrorKind::InvalidData,
                format!("Bad schema file stem: {:?}", i),
            )
        })?
        .to_str()
        .ok_or_else(|| {
            io::Error::new(
                io::ErrorKind::InvalidData,
                format!("Invalid UTF-8 in schema file name: {:?}", i),
            )
        })
}

/// Loads a [Schema] or [Bundle] from path `i` into `bundle`.
///
/// If `i` holds a [Schema], then the file stem of `i` is used as the module name when placing
/// the schema in `bundle`.
///
/// Returns true if it was a schema, false if it was a bundle.
pub fn load_schema_or_bundle(bundle: &mut Map<ModulePath, Schema>, i: &PathBuf) -> io::Result<bool> {
    let mut f = File::open(&i)?;
    let mut bs = vec![];
    f.read_to_end(&mut bs)?;
    load_schema_or_bundle_bin(bundle, bundle_prefix(i)?, &bs[..])
}

/// Loads a [Schema] or [Bundle] from raw binary encoded value `input` into `bundle`.
///
/// If `input` corresponds to a [Schema], then `prefix` is used as its module name; otherwise,
/// it's a [Bundle], and `prefix` is ignored.
///
/// Returns true if it was a schema, false if it was a bundle.
pub fn load_schema_or_bundle_bin(
    bundle: &mut Map<ModulePath, Schema>,
    prefix: &str,
    input: &[u8],
) -> io::Result<bool> {
    let mut src = BytesBinarySource::new(input);
    let mut reader = src.packed_iovalues();
    let blob = reader.demand_next(false)?;
    let language = Language::default();

    if let Ok(s) = language.parse(&blob) {
        bundle.insert(vec![prefix.to_owned()], s);
        Ok(true)
    } else if let Ok(Bundle { modules }) = language.parse(&blob) {
        for (ModulePath(k), v) in modules.0 {
            bundle.insert(k, v);
        }
        Ok(false)
    } else {
        Err(io::Error::new(
            io::ErrorKind::InvalidData,
            format!("Invalid schema binary blob {:?}", prefix),
        ))
    }
}

impl CompilerConfig {
    /// Construct a [CompilerConfig] configured to use `fully_qualified_module_prefix` as the
    /// Rust module prefix for generated code.
    pub fn new(fully_qualified_module_prefix: String) -> Self {
        CompilerConfig {
            bundle: Map::new(),
            fully_qualified_module_prefix,
            support_crate: "preserves_schema".to_owned(),
            external_modules: Map::new(),
            plugins: vec![
                Box::new(types::TypePlugin),
                Box::new(readers::ReaderPlugin),
                Box::new(parsers::ParserPlugin),
                Box::new(unparsers::UnparserPlugin),
            ],
            rustfmt_skip: false,
        }
    }

    pub fn add_external_module(&mut self, m: ExternalModule) {
        let path = m.path.clone();
        if self.external_modules.insert(path.clone(), m).is_some() {
            panic!("Duplicate external module installed: {:?}", path)
        }
    }

    pub fn load_schemas_and_bundles(
        &mut self,
        inputs: &Vec<PathBuf>,
        xrefs: &Vec<PathBuf>,
    ) -> io::Result<()> {
        for i in inputs {
            load_schema_or_bundle_with_purpose(&mut self.bundle, i, Purpose::Codegen)?;
        }
        for i in xrefs {
            load_schema_or_bundle_with_purpose(&mut self.bundle, i, Purpose::Xref)?;
        }
        Ok(())
    }

    pub fn load_xref_bin(&mut self, prefix: &str, bundle_or_schema: &[u8]) -> io::Result<()> {
        load_schema_or_bundle_bin_with_purpose(
            &mut self.bundle,
            prefix,
            bundle_or_schema,
            Purpose::Xref,
        )
    }

    fn build_type_cache(&self) -> Map<Ref, types::TDefinition> {
        self.bundle
            .iter()
            .flat_map(|(modpath, s)| {
                let modpath = ModulePath(modpath.clone());
                s.0.definitions.0.iter().map(move |(name, def)| {
                    let ty = types::definition_type(&modpath, s.1, name, def);
                    (ty.self_ref.clone(), ty)
                })
            })
            .collect()
    }

    fn generate_definition(
        &self,
        b: &mut BundleContext,
        k: &ModulePath,
        v: &Schema,
        n: &str,
        d: &Definition,
        mode: ModuleContextMode,
        generated: &mut Map<ModuleContextMode, Vec<Item>>,
    ) {
        b.generate_module(k, v, mode, generated, |m| {
            for plugin in self.plugins.iter() {
                plugin.generate_definition(m, n, d);
            }
        });
    }
}

/// Expands a vector of [mod@glob]s to a vector of actual paths.
pub fn expand_inputs(globs: &Vec<String>) -> io::Result<Vec<PathBuf>> {
    let mut result = Vec::new();
    for g in globs.iter() {
        for p in
            glob(g).map_err(|e| io::Error::new(io::ErrorKind::InvalidData, format!("{}", e)))?
        {
            result.push(p.map_err(glob::GlobError::into_error)?)
        }
    }
    Ok(result)
}

impl<'a> CodeCollector<'a> {
    /// Construct a [CodeCollector] that collects output Rust modules directly into the file
    /// system tree rooted at `output_dir`.
    pub fn files(output_dir: PathBuf) -> Self {
        CodeCollector {
            emit_mod_declarations: true,
            collect_module: CodeModuleCollector::Files { output_dir },
        }
    }

    #[doc(hidden)]
    pub fn collect_output(&mut self, module: Option<&ModulePath>, contents: &str) -> io::Result<()> {
        match &mut self.collect_module {
            CodeModuleCollector::Files { output_dir } => {
                let mut output_path = output_dir.clone();
                if let Some(k) = module {
                    output_path.extend(k);
                    let module_name = output_path
                        .file_stem()
                        .unwrap()
                        .to_str()
                        .unwrap()
                        .to_owned();
                    let module_name = names::render_modname(&module_name);
                    output_path.set_file_name(format!("{}.rs", module_name));
                } else {
                    output_path.push("mod.rs");
                }
                DirBuilder::new().recursive(true).create(output_path.parent().unwrap())?;

                if output_path.exists() {
                    if let Ok(mut f) = File::open(&output_path) {
                        let mut existing_contents = String::new();
                        f.read_to_string(&mut existing_contents)?;
                        if existing_contents == contents {
                            return Ok(());
                        }
                    }
                }

                let mut f = File::create(output_path)?;
                f.write_all(contents.as_bytes())
            }
            CodeModuleCollector::Custom { collect_output } => {
                collect_output(module, contents)
            }
        }
    }
}

impl Ref {
    pub fn qualify(&self, default_module_path: &schema::ModulePath) -> Ref {
        if self.module.0.is_empty() {
            Ref {
                module: default_module_path.clone(),
                name: self.name.clone(),
            }
        } else {
            self.clone()
        }
    }
}

impl Schema {
    pub fn has_embedded_type(&self) -> bool {
        self.embedded_type != EmbeddedTypeName::False
    }
}

/// Main entry point: runs the compilation process.
pub fn compile<'a>(config: &CompilerConfig, emitter: &mut CodeCollector<'a>) -> io::Result<()> {
    let mut b = BundleContext::new(config);

    for (k, (v, module_purpose)) in config.bundle.iter() {
        if *module_purpose != Purpose::Codegen {
            continue;
        }

        //---------------------------------------------------------------------------

        let mut generated = Map::new();

        b.generate_module(k, v, ModuleContextMode::TargetModule, &mut generated, |m| {
            for plugin in config.plugins.iter() {
                plugin.generate_module(m);
            }
        });

        for (n, d) in &v.definitions.0 {
            use ModuleContextMode::*;
            config.generate_definition(&mut b, k, v, n, d, TargetToplevel, &mut generated);
            config.generate_definition(&mut b, k, v, n, d, TargetGeneric, &mut generated);
        }

        //---------------------------------------------------------------------------

        let mut lines: Vec<String> = Vec::new();

        lines.push(Formatter::to_string(vertical(
            false,
            seq!["#![allow(unused_parens)]", "#![allow(unused_imports)]"],
        )));
        if config.rustfmt_skip {
            lines.push("#![cfg_attr(rustfmt, rustfmt_skip)]".to_owned());
        }
        lines.push(Formatter::to_string(vertical(
            false,
            seq![
                "",
                "use std::convert::TryFrom;",
                format!("use {}::support as _support;", &config.support_crate),
                "use _support::Deserialize;",
                "use _support::Parse;",
                "use _support::Unparse;",
                "use _support::preserves;",
                "use preserves::value::Domain;",
                "use preserves::value::NestedValue;",
                ""
            ],
        )));

        let mut emit_items = |items: Vec<Item>| {
            if !items.is_empty() {
                lines.push(Formatter::to_string(vertical(true, seq(items))));
                lines.push("".to_owned());
            }
        };
        emit_items(generated.remove(&ModuleContextMode::TargetModule).unwrap());
        emit_items(
            generated
                .remove(&ModuleContextMode::TargetToplevel)
                .unwrap(),
        );
        emit_items(generated.remove(&ModuleContextMode::TargetGeneric).unwrap());

        {
            let contents = lines.join("\n");
            emitter.collect_output(Some(k), &contents)?;
        }
    }

    {
        let mut lines = Vec::new();

        if config.rustfmt_skip {
            lines.push("#![cfg_attr(rustfmt, rustfmt_skip)]".to_owned());
            lines.push("".to_owned());
        }

        if emitter.emit_mod_declarations {
            for (modpath, (_, module_purpose)) in config.bundle.iter() {
                if *module_purpose != Purpose::Codegen {
                    continue;
                }
                lines.push(format!(
                    "pub mod {};",
                    names::render_modname(modpath.last().unwrap())
                ));
            }
            lines.push("".to_owned());
        }

        lines.push(format!(
            "use {}::support as _support;",
            &config.support_crate
        ));
        lines.push("use _support::preserves;".to_owned());
        lines.push("".to_owned());

        lines.push("#[allow(non_snake_case)]".to_owned());
        lines.push(Formatter::to_string(item(seq![
            "pub struct ",
            b.language_struct_name(),
            anglebrackets!["N: preserves::value::NestedValue"],
            " ",
            vertical(
                false,
                braces(
                    b.literals
                        .iter()
                        .map(|(value, name)| item(format!("pub {}: N /* {:?} */", name, value)))
                        .collect()
                )
            )
        ])));
        lines.push("".to_owned());
        lines.push(Formatter::to_string(item(seq![
            "impl",
            anglebrackets!["N: preserves::value::NestedValue"],
            " Default for ",
            b.language_struct_name(),
            "<N> ",
            codeblock![seq![
                "fn default() -> Self ",
                codeblock![seq![
                    b.language_struct_name(),
                    " ",
                    vertical(
                        false,
                        braces(
                            b.literals
                                .iter()
                                .map(|(value, name)| {
                                    let bs = preserves::value::PackedWriter::encode_iovalue(&value)
                                        .unwrap();
                                    item(format!(
                                        "{}: /* {:?} */ _support::decode_lit(&{:?}).unwrap()",
                                        name, value, bs
                                    ))
                                })
                                .collect()
                        )
                    )
                ]]
            ]]
        ])));
        lines.push("".to_owned());
        {
            let mut b = Bundle {
                modules: Modules(Map::new()),
            };
            for (modpath, (schema, purpose)) in config.bundle.iter() {
                if *purpose == Purpose::Codegen {
                    b.modules
                        .0
                        .insert(ModulePath(modpath.clone()), schema.clone());
                }
            }
            let b_value = Language::default().unparse(&b);
            let b_bin = preserves::value::PackedWriter::encode_iovalue(&b_value).unwrap();
            let mut hex_encoded_bundle = String::new();
            let mut count = 0;
            for b in b_bin {
                if count % 16 == 0 {
                    hex_encoded_bundle.push_str("\\\n        ");
                }
                count += 1;
                hex_encoded_bundle.push_str(&format!("\\x{:02x}", b));
            }
            lines.push(Formatter::to_string(item(seq![
                "pub fn _bundle() -> &'static [u8] ",
                codeblock![seq!["b\"", hex_encoded_bundle, "\""]]
            ])));
        }
        lines.push("".to_owned());

        let contents = lines.join("\n");
        emitter.collect_output(None, &contents)?;
    }

    Ok(())
}