use crate::{
    module::FuncInfo, plugin::*, tokenizer::is_valid_function_name, Engine, Module, Scope,
};
use core::fmt;
use std::{borrow::Cow, fs, io, path::Path};

impl Engine {
    /// Return [`Definitions`] that can be used to
    /// generate definition files that contain all
    /// the visible items in the engine.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # use rhai::Engine;
    /// # fn main() -> io::Result<()> {
    /// let engine = Engine::new();
    /// engine
    ///     .definitions()
    ///     .write_to_dir(".rhai/definitions")?;
    /// # Ok(())
    /// # }
    /// ```
    pub fn definitions(&self) -> Definitions {
        Definitions {
            engine: self,
            scope: None,
        }
    }

    /// Return [`Definitions`] that can be used to
    /// generate definition files that contain all
    /// the visible items in the engine and the
    /// given scope.
    ///
    /// # Example
    ///
    /// ```no_run
    /// # use rhai::{Engine, Scope};
    /// # fn main() -> io::Result<()> {
    /// let engine = Engine::new();
    /// let scope = Scope::new();
    /// engine
    ///     .definitions_with_scope(&scope)
    ///     .write_to_dir(".rhai/definitions")?;
    /// # Ok(())
    /// # }
    /// ```
    pub fn definitions_with_scope<'e>(&'e self, scope: &'e Scope<'e>) -> Definitions<'e> {
        Definitions {
            engine: self,
            scope: Some(scope),
        }
    }
}

/// Definitions helper that is used to generate
/// definition files based on the contents of an [`Engine`].
#[must_use]
pub struct Definitions<'e> {
    engine: &'e Engine,
    scope: Option<&'e Scope<'e>>,
}

impl<'e> Definitions<'e> {
    /// Write all the definition files to a directory.
    ///
    /// The following separate definition files are generated:
    ///
    /// - `__static__.d.rhai`: globally available items of the engine
    /// - `__scope__.d.rhai`: items in the given scope, if any
    /// - a separate file for each registered module
    pub fn write_to_dir(&self, path: impl AsRef<Path>) -> io::Result<()> {
        let path = path.as_ref();

        fs::create_dir_all(path)?;

        fs::write(path.join("__static__.d.rhai"), self.static_module())?;

        if self.scope.is_some() {
            fs::write(path.join("__scope__.d.rhai"), self.scope())?;
        }

        for (name, decl) in self.modules() {
            fs::write(path.join(format!("{name}.d.rhai")), decl)?;
        }

        Ok(())
    }

    /// Return the definitions for the globally available
    /// items of the engine.
    ///
    /// The definitions will always start with `module static;`.
    #[must_use]
    pub fn static_module(&self) -> String {
        let mut s = String::from("module static;\n\n");

        let mut first = true;
        for m in &self.engine.global_modules {
            if !first {
                s += "\n\n";
            }
            first = false;
            m.write_declaration(&mut s, self).unwrap();
        }

        s
    }

    /// Return the definitions for the available
    /// items of the scope.
    ///
    /// The definitions will always start with `module static;`,
    /// even if the scope is empty or none was provided.
    #[must_use]
    pub fn scope(&self) -> String {
        let mut s = String::from("module static;\n\n");

        if let Some(scope) = self.scope {
            scope.write_declaration(&mut s).unwrap();
        }

        s
    }

    /// Return name and definition pairs for each registered module.
    ///
    /// The definitions will always start with `module <module name>;`.
    #[cfg(not(feature = "no_module"))]
    pub fn modules(&self) -> impl Iterator<Item = (String, String)> + '_ {
        let mut m = self
            .engine
            .global_sub_modules
            .iter()
            .map(move |(name, module)| {
                (
                    name.to_string(),
                    format!("module {name};\n\n{}", module.declaration(self)),
                )
            })
            .collect::<Vec<_>>();

        m.sort_by(|(name1, _), (name2, _)| name1.cmp(name2));

        m.into_iter()
    }
}

impl Module {
    fn declaration(&self, decl: &Definitions) -> String {
        let mut s = String::new();
        self.write_declaration(&mut s, decl).unwrap();
        s
    }

    fn write_declaration(&self, writer: &mut dyn fmt::Write, decl: &Definitions) -> fmt::Result {
        let mut first = true;

        let mut vars = self.iter_var().collect::<Vec<_>>();
        vars.sort_by(|(a, _), (b, _)| a.cmp(b));

        for (name, _) in vars {
            if !first {
                writer.write_str("\n\n")?;
            }
            first = false;

            write!(writer, "const {name}: ?;")?;
        }

        let mut func_infos = self.iter_fn().collect::<Vec<_>>();
        func_infos.sort_by(|a, b| a.metadata.name.cmp(&b.metadata.name));

        for f in func_infos {
            if !first {
                writer.write_str("\n\n")?;
            }
            first = false;

            if f.metadata.access == FnAccess::Private {
                continue;
            }

            f.write_declaration(
                writer,
                decl.engine.custom_keywords.contains_key(&f.metadata.name)
                    || (!f.metadata.name.contains('$')
                        && !is_valid_function_name(&f.metadata.name)),
            )?;
        }

        Ok(())
    }
}

impl FuncInfo {
    fn write_declaration(&self, writer: &mut dyn fmt::Write, operator: bool) -> fmt::Result {
        for comment in &*self.metadata.comments {
            writeln!(writer, "{comment}")?;
        }

        if operator {
            writer.write_str("op ")?;
        } else {
            writer.write_str("fn ")?;
        }

        if let Some(name) = self.metadata.name.strip_prefix("get$") {
            write!(writer, "get {name}(")?;
        } else if let Some(name) = self.metadata.name.strip_prefix("set$") {
            write!(writer, "set {name}(")?;
        } else {
            write!(writer, "{}(", self.metadata.name)?;
        }

        let mut first = true;
        for i in 0..self.metadata.params {
            if !first {
                writer.write_str(", ")?;
            }
            first = false;

            let (param_name, param_type) = self
                .metadata
                .params_info
                .get(i)
                .map(|s| {
                    let mut s = s.split(':');
                    (
                        s.next().unwrap_or("_").split(' ').last().unwrap(),
                        s.next().map(decl_type_name).unwrap_or(Cow::Borrowed("?")),
                    )
                })
                .unwrap_or(("_", "?".into()));

            if operator {
                write!(writer, "{param_type}")?;
            } else {
                write!(writer, "{param_name}: {param_type}")?;
            }
        }

        write!(
            writer,
            ") -> {};",
            decl_type_name(&self.metadata.return_type)
        )?;

        Ok(())
    }
}

/// We have to transform some of the types.
///
/// This is highly inefficient and is currently based on
/// trial and error with the core packages.
///
/// It tries to flatten types, removing `&` and `&mut`,
/// and paths, while keeping generics.
///
/// Associated generic types are also rewritten into regular
/// generic type parameters.
fn decl_type_name(ty: &str) -> Cow<str> {
    let ty = ty.replace("crate::", "");
    let ty = ty.split("::").last().unwrap();
    let ty = ty.trim();
    let ty = ty.strip_prefix("&mut").unwrap_or(ty).trim();

    let ty = ty
        .strip_prefix("RhaiResultOf<")
        .and_then(|s| s.strip_suffix('>'))
        .map(str::trim)
        .unwrap_or(ty);

    // FIXME(tamasfe): some of the given types are unusable,
    // e.g. "Range<crate" is the entire type this function receives,
    // same with "crate", I have no idea where these come from.
    ty.replace("Range<crate", "?")
        .replace("crate", "?")
        .replace("Iterator<Item=", "Iterator<")
        .replace("Dynamic", "?")
        .replace("INT", "int")
        .replace("FLOAT", "float")
        .replace("&str", "String")
        .replace("ImmutableString", "String")
        .into()
}

impl Scope<'_> {
    fn write_declaration(&self, writer: &mut dyn fmt::Write) -> fmt::Result {
        let mut first = true;
        for (name, constant, _) in self.iter_raw() {
            if !first {
                writer.write_str("\n\n")?;
            }
            first = false;

            let kw = if constant { "const" } else { "let" };

            write!(writer, "{kw} {name};")?;
        }

        Ok(())
    }
}