/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! # Function definitions for a `ComponentInterface`.
//!
//! This module converts function definitions from UDL into structures that
//! can be added to a `ComponentInterface`. A declaration in the UDL like this:
//!
//! ```
//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
//! namespace example {
//!     string hello();
//! };
//! # "##, "crate_name")?;
//! # Ok::<(), anyhow::Error>(())
//! ```
//!
//! Will result in a [`Function`] member being added to the resulting [`crate::ComponentInterface`]:
//!
//! ```
//! # use uniffi_bindgen::interface::Type;
//! # let ci = uniffi_bindgen::interface::ComponentInterface::from_webidl(r##"
//! # namespace example {
//! #     string hello();
//! # };
//! # "##, "crate_name")?;
//! let func = ci.get_function_definition("hello").unwrap();
//! assert_eq!(func.name(), "hello");
//! assert!(matches!(func.return_type(), Some(Type::String)));
//! assert_eq!(func.arguments().len(), 0);
//! # Ok::<(), anyhow::Error>(())
//! ```

use anyhow::Result;

use super::ffi::{FfiArgument, FfiFunction, FfiType};
use super::{AsType, ComponentInterface, Literal, ObjectImpl, Type, TypeIterator};
use uniffi_meta::Checksum;

/// Represents a standalone function.
///
/// Each `Function` corresponds to a standalone function in the rust module,
/// and has a corresponding standalone function in the foreign language bindings.
///
/// In the FFI, this will be a standalone function with appropriately lowered types.
#[derive(Debug, Clone, Checksum)]
pub struct Function {
    pub(super) name: String,
    pub(super) module_path: String,
    pub(super) is_async: bool,
    pub(super) arguments: Vec<Argument>,
    pub(super) return_type: Option<Type>,
    // We don't include the FFIFunc in the hash calculation, because:
    //  - it is entirely determined by the other fields,
    //    so excluding it is safe.
    //  - its `name` property includes a checksum derived from the very
    //    hash value we're trying to calculate here, so excluding it
    //    avoids a weird circular dependency in the calculation.
    #[checksum_ignore]
    pub(super) ffi_func: FfiFunction,
    #[checksum_ignore]
    pub(super) docstring: Option<String>,
    pub(super) throws: Option<Type>,
    pub(super) checksum_fn_name: String,
    // Force a checksum value, or we'll fallback to the trait.
    #[checksum_ignore]
    pub(super) checksum: Option<u16>,
}

impl Function {
    pub fn name(&self) -> &str {
        &self.name
    }

    pub fn is_async(&self) -> bool {
        self.is_async
    }

    pub fn arguments(&self) -> Vec<&Argument> {
        self.arguments.iter().collect()
    }

    pub fn full_arguments(&self) -> Vec<Argument> {
        self.arguments.to_vec()
    }

    pub fn return_type(&self) -> Option<&Type> {
        self.return_type.as_ref()
    }

    pub fn ffi_func(&self) -> &FfiFunction {
        &self.ffi_func
    }

    pub fn checksum_fn_name(&self) -> &str {
        &self.checksum_fn_name
    }

    pub fn checksum(&self) -> u16 {
        self.checksum.unwrap_or_else(|| uniffi_meta::checksum(self))
    }

    pub fn throws(&self) -> bool {
        self.throws.is_some()
    }

    pub fn throws_name(&self) -> Option<&str> {
        super::throws_name(&self.throws)
    }

    pub fn throws_type(&self) -> Option<&Type> {
        self.throws.as_ref()
    }

    pub fn derive_ffi_func(&mut self) -> Result<()> {
        assert!(!self.ffi_func.name.is_empty());
        self.ffi_func.init(
            self.return_type.as_ref().map(Into::into),
            self.arguments.iter().map(Into::into),
        );
        Ok(())
    }

    pub fn iter_types(&self) -> TypeIterator<'_> {
        Box::new(
            self.arguments
                .iter()
                .flat_map(Argument::iter_types)
                .chain(self.return_type.iter().flat_map(Type::iter_types)),
        )
    }

    pub fn docstring(&self) -> Option<&str> {
        self.docstring.as_deref()
    }
}

impl From<uniffi_meta::FnParamMetadata> for Argument {
    fn from(meta: uniffi_meta::FnParamMetadata) -> Self {
        Argument {
            name: meta.name,
            type_: meta.ty,
            by_ref: meta.by_ref,
            optional: meta.optional,
            default: meta.default,
        }
    }
}

impl From<uniffi_meta::FnMetadata> for Function {
    fn from(meta: uniffi_meta::FnMetadata) -> Self {
        let ffi_name = meta.ffi_symbol_name();
        let checksum_fn_name = meta.checksum_symbol_name();
        let is_async = meta.is_async;
        let return_type = meta.return_type.map(Into::into);
        let arguments = meta.inputs.into_iter().map(Into::into).collect();

        let ffi_func = FfiFunction {
            name: ffi_name,
            is_async,
            ..FfiFunction::default()
        };

        Self {
            name: meta.name,
            module_path: meta.module_path,
            is_async,
            arguments,
            return_type,
            ffi_func,
            docstring: meta.docstring.clone(),
            throws: meta.throws,
            checksum_fn_name,
            checksum: meta.checksum,
        }
    }
}

/// Represents an argument to a function/constructor/method call.
///
/// Each argument has a name and a type, along with some optional metadata.
#[derive(Debug, Clone, Checksum)]
pub struct Argument {
    pub(super) name: String,
    pub(super) type_: Type,
    pub(super) by_ref: bool,
    pub(super) optional: bool,
    pub(super) default: Option<Literal>,
}

impl Argument {
    pub fn name(&self) -> &str {
        &self.name
    }

    pub fn by_ref(&self) -> bool {
        self.by_ref
    }

    pub fn is_trait_ref(&self) -> bool {
        matches!(&self.type_, Type::Object { imp, .. } if *imp == ObjectImpl::Trait)
    }

    pub fn default_value(&self) -> Option<&Literal> {
        self.default.as_ref()
    }

    pub fn iter_types(&self) -> TypeIterator<'_> {
        self.type_.iter_types()
    }
}

impl AsType for Argument {
    fn as_type(&self) -> Type {
        self.type_.clone()
    }
}

impl From<&Argument> for FfiArgument {
    fn from(a: &Argument) -> FfiArgument {
        FfiArgument {
            name: a.name.clone(),
            type_: (&a.type_).into(),
        }
    }
}

/// Combines the return and throws type of a function/method
#[derive(Debug, PartialOrd, Ord, PartialEq, Eq)]
pub struct ResultType {
    pub return_type: Option<Type>,
    pub throws_type: Option<Type>,
}

impl ResultType {
    /// Get the `T` parameters for the `FutureCallback<T>` for this ResultType
    pub fn future_callback_param(&self) -> FfiType {
        match &self.return_type {
            Some(t) => t.into(),
            None => FfiType::UInt8,
        }
    }
}

/// Implemented by function-like types (Function, Method, Constructor)
pub trait Callable {
    fn arguments(&self) -> Vec<&Argument>;
    fn return_type(&self) -> Option<Type>;
    fn throws_type(&self) -> Option<Type>;
    fn is_async(&self) -> bool;
    fn takes_self(&self) -> bool {
        false
    }
    fn result_type(&self) -> ResultType {
        ResultType {
            return_type: self.return_type(),
            throws_type: self.throws_type(),
        }
    }

    // Quick way to get the rust future scaffolding function that corresponds to our return type.

    fn ffi_rust_future_poll(&self, ci: &ComponentInterface) -> String {
        ci.ffi_rust_future_poll(self.return_type().map(Into::into))
            .name()
            .to_owned()
    }

    fn ffi_rust_future_cancel(&self, ci: &ComponentInterface) -> String {
        ci.ffi_rust_future_cancel(self.return_type().map(Into::into))
            .name()
            .to_owned()
    }

    fn ffi_rust_future_complete(&self, ci: &ComponentInterface) -> String {
        ci.ffi_rust_future_complete(self.return_type().map(Into::into))
            .name()
            .to_owned()
    }

    fn ffi_rust_future_free(&self, ci: &ComponentInterface) -> String {
        ci.ffi_rust_future_free(self.return_type().map(Into::into))
            .name()
            .to_owned()
    }
}

impl Callable for Function {
    fn arguments(&self) -> Vec<&Argument> {
        self.arguments()
    }

    fn return_type(&self) -> Option<Type> {
        self.return_type().cloned()
    }

    fn throws_type(&self) -> Option<Type> {
        self.throws_type().cloned()
    }

    fn is_async(&self) -> bool {
        self.is_async
    }
}

// Needed because Askama likes to add extra refs to variables
impl<T: Callable> Callable for &T {
    fn arguments(&self) -> Vec<&Argument> {
        (*self).arguments()
    }

    fn return_type(&self) -> Option<Type> {
        (*self).return_type()
    }

    fn throws_type(&self) -> Option<Type> {
        (*self).throws_type()
    }

    fn is_async(&self) -> bool {
        (*self).is_async()
    }

    fn takes_self(&self) -> bool {
        (*self).takes_self()
    }
}

#[cfg(test)]
mod test {
    use super::super::ComponentInterface;
    use super::*;

    #[test]
    fn test_minimal_and_rich_function() -> Result<()> {
        let ci = ComponentInterface::from_webidl(
            r#"
            namespace test {
                void minimal();
                [Throws=TestError]
                sequence<string?> rich(u32 arg1, TestDict arg2);
            };
            [Error]
            enum TestError { "err" };
            dictionary TestDict {
                u32 field;
            };
        "#,
            "crate_name",
        )?;

        let func1 = ci.get_function_definition("minimal").unwrap();
        assert_eq!(func1.name(), "minimal");
        assert!(func1.return_type().is_none());
        assert!(func1.throws_type().is_none());
        assert_eq!(func1.arguments().len(), 0);

        let func2 = ci.get_function_definition("rich").unwrap();
        assert_eq!(func2.name(), "rich");
        assert_eq!(
            func2.return_type().unwrap(),
            &Type::Sequence {
                inner_type: Box::new(Type::Optional {
                    inner_type: Box::new(Type::String)
                })
            }
        );
        assert!(
            matches!(func2.throws_type(), Some(Type::Enum { name, .. }) if name == "TestError" && ci.is_name_used_as_error(name))
        );
        assert_eq!(func2.arguments().len(), 2);
        assert_eq!(func2.arguments()[0].name(), "arg1");
        assert_eq!(func2.arguments()[0].as_type(), Type::UInt32);
        assert_eq!(func2.arguments()[1].name(), "arg2");
        assert!(
            matches!(func2.arguments()[1].as_type(), Type::Record { name, .. } if name == "TestDict")
        );
        Ok(())
    }

    #[test]
    fn test_docstring_function() {
        const UDL: &str = r#"
            namespace test {
                /// informative docstring
                void testing();
            };
        "#;
        let ci = ComponentInterface::from_webidl(UDL, "crate_name").unwrap();
        assert_eq!(
            ci.get_function_definition("testing")
                .unwrap()
                .docstring()
                .unwrap(),
            "informative docstring"
        );
    }
}