/*!

A trait denoting a type can possibly be mapped to an SQL type

> Like all of the [`sql_entity_graph`][crate::sql_entity_graph] APIs, this is considered **internal**
to the `pgx` framework and very subject to change between versions. While you may use this, please do it with caution.

*/
use std::error::Error;

use super::return_variant::ReturnsError;
use super::{FunctionMetadataTypeEntity, Returns};

#[derive(Clone, Copy, Debug, Hash, Ord, PartialOrd, PartialEq, Eq)]
pub enum ArgumentError {
    SetOf,
    Table,
    BareU8,
    SkipInArray,
    Datum,
}

impl std::fmt::Display for ArgumentError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            ArgumentError::SetOf => {
                write!(f, "Cannot use SetOfIterator as an argument")
            }
            ArgumentError::Table => {
                write!(f, "Cannot use TableIterator as an argument")
            }
            ArgumentError::BareU8 => {
                write!(f, "Cannot use bare u8")
            }
            ArgumentError::SkipInArray => {
                write!(f, "SqlMapping::Skip inside Array is not valid")
            }
            ArgumentError::Datum => {
                write!(f, "A Datum as an argument means that `sql = \"...\"` must be set in the declaration")
            }
        }
    }
}

/// Describes ways that Rust types are mapped into SQL
#[derive(Clone, Debug, Hash, Eq, PartialEq, Ord, PartialOrd)]
pub enum SqlMapping {
    /// Explicit mappings provided by PGX
    As(String),
    Composite {
        array_brackets: bool,
    },
    /// Some types are still directly from source
    Source {
        array_brackets: bool,
    },
    /// Placeholder for some types with no simple translation
    Skip,
}

impl SqlMapping {
    pub fn literal(s: &'static str) -> SqlMapping {
        SqlMapping::As(String::from(s))
    }
}

impl Error for ArgumentError {}

/**
A value which can be represented in SQL

# Safety

By implementing this, you assert you are not lying to either Postgres or Rust in doing so.
This trait asserts a safe translation exists between values of this type from Rust to SQL,
or from SQL into Rust. If you are mistaken about how this works, either the Postgres C API
or the Rust handling in PGX may emit undefined behavior.

It cannot be made private or sealed due to details of the structure of the PGX framework.
Nonetheless, if you are not confident the translation is valid: do not implement this trait.
*/
pub unsafe trait SqlTranslatable {
    fn type_name() -> &'static str {
        core::any::type_name::<Self>()
    }
    fn argument_sql() -> Result<SqlMapping, ArgumentError>;
    fn return_sql() -> Result<Returns, ReturnsError>;
    fn variadic() -> bool {
        false
    }
    fn optional() -> bool {
        false
    }
    fn entity() -> FunctionMetadataTypeEntity {
        FunctionMetadataTypeEntity {
            type_name: Self::type_name(),
            argument_sql: Self::argument_sql(),
            return_sql: Self::return_sql(),
            variadic: Self::variadic(),
            optional: Self::optional(),
        }
    }
}

unsafe impl<T> SqlTranslatable for Option<T>
where
    T: SqlTranslatable,
{
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        T::argument_sql()
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        T::return_sql()
    }
    fn optional() -> bool {
        true
    }
}

unsafe impl<T> SqlTranslatable for *mut T
where
    T: SqlTranslatable,
{
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        T::argument_sql()
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        T::return_sql()
    }
    fn optional() -> bool {
        T::optional()
    }
}

unsafe impl<T, E> SqlTranslatable for Result<T, E>
where
    T: SqlTranslatable,
    E: std::error::Error + 'static,
{
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        T::argument_sql()
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        T::return_sql()
    }
    fn optional() -> bool {
        true
    }
}

unsafe impl<T> SqlTranslatable for Vec<T>
where
    T: SqlTranslatable,
{
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        match T::type_name() {
            id if id == u8::type_name() => Ok(SqlMapping::As(format!("bytea"))),
            _ => match T::argument_sql() {
                Ok(SqlMapping::As(val)) => Ok(SqlMapping::As(format!("{val}[]"))),
                Ok(SqlMapping::Composite { array_brackets: _ }) => {
                    Ok(SqlMapping::Composite { array_brackets: true })
                }
                Ok(SqlMapping::Source { array_brackets: _ }) => {
                    Ok(SqlMapping::Source { array_brackets: true })
                }
                Ok(SqlMapping::Skip) => Ok(SqlMapping::Skip),
                err @ Err(_) => err,
            },
        }
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        match T::type_name() {
            id if id == u8::type_name() => Ok(Returns::One(SqlMapping::As(format!("bytea")))),
            _ => match T::return_sql() {
                Ok(Returns::One(SqlMapping::As(val))) => {
                    Ok(Returns::One(SqlMapping::As(format!("{val}[]"))))
                }
                Ok(Returns::One(SqlMapping::Composite { array_brackets: _ })) => {
                    Ok(Returns::One(SqlMapping::Composite { array_brackets: true }))
                }
                Ok(Returns::One(SqlMapping::Source { array_brackets: _ })) => {
                    Ok(Returns::One(SqlMapping::Source { array_brackets: true }))
                }
                Ok(Returns::One(SqlMapping::Skip)) => Ok(Returns::One(SqlMapping::Skip)),
                Ok(Returns::SetOf(_)) => Err(ReturnsError::SetOfInArray),
                Ok(Returns::Table(_)) => Err(ReturnsError::TableInArray),
                err @ Err(_) => err,
            },
        }
    }
    fn optional() -> bool {
        T::optional()
    }
}

unsafe impl SqlTranslatable for u8 {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Err(ArgumentError::BareU8)
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Err(ReturnsError::BareU8)
    }
}

unsafe impl SqlTranslatable for i32 {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("INT"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("INT")))
    }
}

unsafe impl SqlTranslatable for u32 {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::Source { array_brackets: false })
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::Source { array_brackets: false }))
    }
}

unsafe impl SqlTranslatable for String {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("TEXT"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("TEXT")))
    }
}

unsafe impl<T> SqlTranslatable for &T
where
    T: SqlTranslatable,
{
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        T::argument_sql()
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        T::return_sql()
    }
}

unsafe impl<'a> SqlTranslatable for &'a str {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("TEXT"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("TEXT")))
    }
}

unsafe impl<'a> SqlTranslatable for &'a [u8] {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("bytea"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("bytea")))
    }
}

unsafe impl SqlTranslatable for i8 {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::As(String::from("\"char\"")))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::As(String::from("\"char\""))))
    }
}

unsafe impl SqlTranslatable for i16 {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("smallint"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("smallint")))
    }
}

unsafe impl SqlTranslatable for i64 {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("bigint"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("bigint")))
    }
}

unsafe impl SqlTranslatable for bool {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("bool"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("bool")))
    }
}

unsafe impl SqlTranslatable for char {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("varchar"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("varchar")))
    }
}

unsafe impl SqlTranslatable for f32 {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("real"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("real")))
    }
}

unsafe impl SqlTranslatable for f64 {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("double precision"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("double precision")))
    }
}

unsafe impl SqlTranslatable for std::ffi::CStr {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("cstring"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("cstring")))
    }
}

unsafe impl SqlTranslatable for &'static std::ffi::CStr {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("cstring"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("cstring")))
    }
}

unsafe impl SqlTranslatable for &'static cstr_core::CStr {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("cstring"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("cstring")))
    }
}

unsafe impl SqlTranslatable for cstr_core::CStr {
    fn argument_sql() -> Result<SqlMapping, ArgumentError> {
        Ok(SqlMapping::literal("cstring"))
    }
    fn return_sql() -> Result<Returns, ReturnsError> {
        Ok(Returns::One(SqlMapping::literal("cstring")))
    }
}