litext 1.2.1

use crate::literal::LitStr;

use std::{fmt::Display, str::FromStr};

use proc_macro2::{Ident, Literal, Span, TokenStream};

#[doc(hidden)]
mod __private {
    pub trait IntegerSeal {
        fn is_signed() -> bool {
            false
        }
    }
    pub trait FloatSeal {}

    impl IntegerSeal for i8 {
        fn is_signed() -> bool {
            true
        }
    }
    impl IntegerSeal for i16 {
        fn is_signed() -> bool {
            true
        }
    }
    impl IntegerSeal for i32 {
        fn is_signed() -> bool {
            true
        }
    }
    impl IntegerSeal for i64 {
        fn is_signed() -> bool {
            true
        }
    }
    impl IntegerSeal for i128 {
        fn is_signed() -> bool {
            true
        }
    }
    impl IntegerSeal for isize {
        fn is_signed() -> bool {
            true
        }
    }
    impl IntegerSeal for u8 {}
    impl IntegerSeal for u16 {}
    impl IntegerSeal for u32 {}
    impl IntegerSeal for u64 {}
    impl IntegerSeal for u128 {}
    impl IntegerSeal for usize {}

    impl FloatSeal for f32 {}
    impl FloatSeal for f64 {}
}

/// Converts literal tokens into typed values.
///
/// This trait is the core extension point for `litext`. Implementing it enables
/// `litext!(input as MyType)` to work for custom types.
///
/// # Implementations
///
/// The trait is automatically implemented for all built-in literal types:
/// - Strings: [`String`], [`LitStr`]
/// - Integers: `i8`–`i128`, `isize`, `u8`–`u128`, `usize`, [`LitInt<T>`]
/// - Floats: `f32`, `f64`, [`LitFloat<T>`]
/// - Characters: [`char`], [`LitChar`]
/// - Booleans: [`bool`], [`LitBool`]
/// - Bytes: `u8`, [`LitByte`], `Vec<u8>`, [`LitByteStr`]
/// - C Strings: [`CString`], [`LitCStr`]
///
/// # Method Overview
///
/// - [`from_lit`](Self::from_lit) handles literal tokens (`"hello"`, `42`, `3.14`)
/// - [`from_ident`](Self::from_ident) handles identifier tokens (`true`, `false`)
/// - [`from_negative_lit`](Self::from_negative_lit) handles negative literals (`-42`)
///
/// Override `from_ident` for types represented as identifiers (like `bool`).
/// Override `from_negative_lit` for signed numeric types. The default
/// implementations return errors, which is correct for non-numeric types.
///
/// # Example
///
/// ```ignore
/// use litext::literal::FromLit;
/// use proc_macro2::{Literal, TokenStream};
///
/// pub struct UpperString(String);
///
/// impl FromLit for UpperString {
///     fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
///         let s = String::from_lit(lit)?;
///         Ok(UpperString(s.to_uppercase()))
///     }
/// }
///
/// // Then in your macro:
/// // let val: UpperString = litext!(input as UpperString);
/// ```
///
/// # See Also
///
/// - [`crate::extract`] for the function that drives extraction
/// - [`ToTokens`](super::ToTokens) for the reverse direction
pub trait FromLit: Sized {
    /// Attempts to extract a value from a [`Literal`] token.
    ///
    /// On success, returns `Ok` containing the extracted value.
    ///
    /// # Errors
    ///
    /// On failure, returns `Err` containing a `TokenStream` that triggers a
    /// compile error when returned from a proc-macro.
    fn from_lit(lit: Literal) -> Result<Self, TokenStream>;

    /// Attempts to extract a value from an [`Ident`] token.
    ///
    /// Most types will never receive an ident, the default implementation
    /// returns an error. Override this for types like `bool` where the
    /// literal representation is an identifier (`true`, `false`).
    ///
    /// # Errors
    ///
    /// Errors to this function is in the form of a `compile_error!()` token stream, the cause
    /// completely up to the implementer.
    #[inline]
    fn from_ident(ident: Ident) -> Result<Self, TokenStream> {
        Err(comperr::error(
            ident.span(),
            format!("expected a literal, found identifier `{ident}`"),
        ))
    }

    /// Attempts to extract a value from a negative [`Literal`] token.
    ///
    /// A 'negative Literal' token in this case is the negative number,
    /// a dash punctuation followed by a number. Most types won't accept or receive
    /// a negative literal. Override this for signed integer / float types where it accepts negatives
    /// as a value.
    ///
    /// # Errors
    ///
    /// Errors to this function is in the form of a `compile_error!()` token stream, the cause
    /// completely up to the implementer.
    #[inline]
    fn from_negative_lit(lit: Literal) -> Result<Self, TokenStream> {
        Err(comperr::error(lit.span(), "unexpected negative literal"))
    }
}

/// Strips integer type suffixes and prefix notation from a raw integer literal string.
///
/// Returns `Some((digits, radix, suffix))` where digits are the base-N digits with
/// underscores removed, radix is 2/8/10/16, and suffix is the optional type suffix
/// like `"u8"` or `"i32"`. Returns `None` for malformed input.
fn parse_int_raw(raw: &str) -> Option<(String, u32, Option<String>)> {
    let suffixes = [
        "i8", "i16", "i32", "i64", "i128", "isize", "u8", "u16", "u32", "u64", "u128", "usize",
    ];
    let mut s = raw;
    let mut found_suffix: Option<String> = None;
    for suffix in suffixes {
        if let Some(stripped) = s.strip_suffix(suffix) {
            s = stripped;
            found_suffix = Some(suffix.to_string());
            break;
        }
    }

    let (digits, radix) = if let Some(rest) = s.strip_prefix("0x").or_else(|| s.strip_prefix("0X"))
    {
        (rest, 16)
    } else if let Some(rest) = s.strip_prefix("0o").or_else(|| s.strip_prefix("0O")) {
        (rest, 8)
    } else if let Some(rest) = s.strip_prefix("0b").or_else(|| s.strip_prefix("0B")) {
        (rest, 2)
    } else {
        (s, 10)
    };

    let cleaned: String = if digits.contains('_') {
        let s: String = digits.chars().filter(|c| *c != '_').collect();
        if s.is_empty() {
            return None;
        }
        s
    } else {
        if digits.is_empty() {
            return None;
        }
        digits.to_string()
    };
    Some((cleaned, radix, found_suffix))
}

/// Strips the optional float type suffix (`f32`/`f64`) and underscore separators.
fn parse_float_raw(raw: &str) -> (String, Option<String>) {
    let suffixes = ["f32", "f64"];
    let mut s = raw;
    let mut found_suffix: Option<String> = None;
    for suffix in suffixes {
        if let Some(stripped) = s.strip_suffix(suffix) {
            s = stripped;
            found_suffix = Some(suffix.to_string());
            break;
        }
    }
    let cleaned = if s.contains('_') {
        s.chars().filter(|c| *c != '_').collect()
    } else {
        s.to_string()
    };
    (cleaned, found_suffix)
}

// ---------------------------------------------------------------------------
// Strings
// ---------------------------------------------------------------------------

impl FromLit for String {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        crate::parse_lit(&lit)
    }
}

impl FromLit for LitStr {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        let span = lit.span();
        let value = crate::parse_lit(&lit)?;
        Ok(LitStr::new(value, span))
    }
}

// ---------------------------------------------------------------------------
// LitInt
// ---------------------------------------------------------------------------

/// A parsed integer literal bundled with its source location.
///
/// Use `LitInt<T>` when you need the span for diagnostics. The type parameter
/// `T` must be one of the sealed integer types:
/// - Signed: `i8`, `i16`, `i32`, `i64`, `i128`, `isize`
/// - Unsigned: `u8`, `u16`, `u32`, `u64`, `u128`, `usize`
///
/// Defaults to `i32` when using `LitInt` without a type parameter.
///
/// # Supported Formats
///
/// | Format | Example |
/// |--------|---------|
/// | Decimal | `42` |
/// | Hexadecimal | `0xFF`, `0XFF` |
/// | Octal | `0o77`, `0O77` |
/// | Binary | `0b1010`, `0B1010` |
/// | Underscores | `1_000_000` |
/// | Type suffix | `42u8`, `255i32` |
///
/// Overflow triggers a compile error.
///
/// # Example
///
/// ```ignore
/// use litext::{litext, TokenStream};
/// use litext::literal::LitInt;
///
/// pub fn my_macro(input: TokenStream) -> TokenStream {
///     let lit: LitInt<u8> = litext!(input as LitInt<u8>);
///     if *lit.value() == 0 {
///         return comperr::error(lit.span(), "value cannot be zero");
///     }
///     quote::quote! { /* use lit.value() */ }
/// }
/// ```
pub struct LitInt<T: __private::IntegerSeal = i32> {
    /// The parsed integer value.
    pub value: T,
    /// The source location of the literal.
    pub span: Span,
    /// The type suffix if explicitly written, e.g. `Some("u8")` for `42u8`,
    /// or `None` for `42`.
    pub suffix: Option<String>,
}

impl<T> LitInt<T>
where
    T: __private::IntegerSeal,
{
    /// Creates a new [`LitInt`] from a value and a span.
    pub fn new(value: T, span: Span, suffix: Option<String>) -> Self {
        Self {
            value,
            span,
            suffix,
        }
    }

    /// Returns the parsed integer value.
    pub fn value(&self) -> &T {
        &self.value
    }

    /// Returns the source span of the literal.
    pub fn span(&self) -> Span {
        self.span
    }

    /// Returns the explicit type suffix if present.
    ///
    /// For `42u8` this returns `Some("u8")`.
    /// For `42` this returns `None`.
    pub fn suffix(&self) -> Option<&str> {
        self.suffix.as_deref()
    }
}

impl<T> FromLit for LitInt<T>
where
    T: TryFrom<u128> + TryFrom<i128> + __private::IntegerSeal,
    <T as TryFrom<u128>>::Error: Display,
    <T as TryFrom<i128>>::Error: Display,
{
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        let span = lit.span();
        let raw = lit.to_string();
        let (digits, radix, suffix) =
            parse_int_raw(&raw).ok_or_else(|| comperr::error(span, "malformed integer literal"))?;

        let value: T = if let Ok(n) = u128::from_str_radix(&digits, radix) {
            T::try_from(n)
                .map_err(|e| comperr::error(span, format!("integer out of range: {e}")))?
        } else if let Ok(n) = i128::from_str_radix(&digits, radix) {
            T::try_from(n)
                .map_err(|e| comperr::error(span, format!("integer out of range: {e}")))?
        } else {
            return Err(comperr::error(span, "malformed integer literal"));
        };

        Ok(LitInt::new(value, span, suffix))
    }

    #[inline]
    // use of allow: the function checked for all possible failures that clippy::pedantic is being pedantic about
    #[allow(clippy::cast_sign_loss, clippy::cast_possible_wrap)]
    fn from_negative_lit(lit: Literal) -> Result<Self, TokenStream> {
        if !T::is_signed() {
            return Err(comperr::error(
                lit.span(),
                "cannot negate an unsigned integer",
            ));
        }
        let span = lit.span();
        let raw = lit.to_string();
        let (digits, radix, suffix) =
            parse_int_raw(&raw).ok_or_else(|| comperr::error(span, "malformed integer literal"))?;
        let n = u128::from_str_radix(&digits, radix)
            .map_err(|_| comperr::error(span, "malformed integer literal"))?;
        let negated = if n == (i128::MIN as u128) {
            i128::MIN
        } else if n > (i128::MAX as u128) {
            return Err(comperr::error(span, "integer out of range"));
        } else {
            -(n as i128)
        };
        let value = T::try_from(negated)
            .map_err(|e| comperr::error(span, format!("integer out of range: {e}")))?;
        Ok(LitInt::new(value, span, suffix))
    }
}

// ---------------------------------------------------------------------------
// Plain integer impls
// ---------------------------------------------------------------------------

macro_rules! impl_from_lit_int_signed {
    ($($t:ty),*) => {
        $(impl FromLit for $t {
            #[inline]
            fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
                Ok(LitInt::<$t>::from_lit(lit)?.value)
            }
            #[inline]
            fn from_negative_lit(lit: Literal) -> Result<Self, TokenStream> {
                Ok(LitInt::<$t>::from_negative_lit(lit)?.value)
            }
        })*
    };
}

macro_rules! impl_from_lit_int_unsigned {
    ($($t:ty),*) => {
        $(impl FromLit for $t {
            #[inline]
            fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
                Ok(LitInt::<$t>::from_lit(lit)?.value)
            }
            #[inline]
            fn from_negative_lit(lit: Literal) -> Result<Self, TokenStream> {
                Err(comperr::error(lit.span(), "cannot negate an unsigned integer"))
            }
        })*
    };
}

impl_from_lit_int_signed!(i8, i16, i32, i64, i128, isize);
impl_from_lit_int_unsigned!(u16, u32, u64, u128, usize);

impl FromLit for u8 {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        let raw = lit.to_string();
        if raw.starts_with("b'") {
            let span = lit.span();
            let inner = raw
                .strip_prefix("b'")
                .and_then(|s| s.strip_suffix('\''))
                .ok_or_else(|| comperr::error(span, "expected a byte literal"))?;
            let bytes = crate::unescape_bytes(inner, span)?;
            if bytes.len() != 1 {
                return Err(comperr::error(span, "invalid byte literal"));
            }
            return Ok(bytes[0]);
        }
        Ok(*LitInt::<u8>::from_lit(lit)?.value())
    }

    #[inline]
    fn from_negative_lit(lit: Literal) -> Result<Self, TokenStream> {
        Err(comperr::error(
            lit.span(),
            "cannot negate an unsigned integer",
        ))
    }
}

// ---------------------------------------------------------------------------
// LitFloat
// ---------------------------------------------------------------------------

/// A parsed float literal bundled with its source location.
///
/// Use `LitFloat<T>` when you need the span for diagnostics. `T` must be
/// `f32` or `f64`. Defaults to `f64`.
///
/// # Supported Formats
///
/// | Format | Example |
/// |--------|---------|
/// | Standard | `3.14`, `3.0` |
/// | Scientific | `1e10`, `2.5e-3`, `1E10` |
/// | Underscores | `1_000.5` |
/// | Type suffix | `3.14f32`, `1e10f64` |
///
/// Parsing delegates to `T::from_str`.
///
/// # Example
///
/// ```ignore
/// use litext::{litext, TokenStream};
/// use litext::literal::LitFloat;
///
/// pub fn my_macro(input: TokenStream) -> TokenStream {
///     let lit: LitFloat<f32> = litext!(input as LitFloat<f32>);
///     if *lit.value() < 0.0 {
///         return comperr::error(lit.span(), "expected non-negative float");
///     }
///     quote::quote! { /* use lit.value() */ }
/// }
/// ```
pub struct LitFloat<T: __private::FloatSeal = f64> {
    /// The parsed float value.
    pub value: T,
    /// The source location of the literal.
    pub span: Span,
    /// The type suffix if explicitly written, e.g. `Some("f32")` for `3.14f32`,
    /// or `None` for `3.14`.
    pub suffix: Option<String>,
}
impl<T> LitFloat<T>
where
    T: __private::FloatSeal,
{
    /// Creates a new [`LitFloat`] from a value and a span.
    pub fn new(value: T, span: Span, suffix: Option<String>) -> Self {
        Self {
            value,
            span,
            suffix,
        }
    }

    /// Returns the parsed float value.
    pub fn value(&self) -> &T {
        &self.value
    }

    /// Returns the source span of the literal.
    pub fn span(&self) -> Span {
        self.span
    }

    /// Returns the explicit type suffix if present.
    ///
    /// For `42f32` this returns `Some("f32")`.
    /// For `42.0` this returns `None`.
    pub fn suffix(&self) -> Option<&str> {
        self.suffix.as_deref()
    }
}

impl<T> FromLit for LitFloat<T>
where
    T: __private::FloatSeal + std::ops::Neg<Output = T>,
    T: FromStr,
    T::Err: Display,
{
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        let span = lit.span();
        let raw = lit.to_string();
        let (cleaned, suffix) = parse_float_raw(&raw);
        let value = cleaned
            .parse::<T>()
            .map_err(|e| comperr::error(span, format!("malformed float literal: {e}")))?;
        Ok(LitFloat::new(value, span, suffix))
    }

    #[inline]
    fn from_negative_lit(lit: Literal) -> Result<Self, TokenStream> {
        let span = lit.span();
        let raw = lit.to_string();
        let (cleaned, suffix) = parse_float_raw(&raw);
        let value = cleaned
            .parse::<T>()
            .map_err(|e| comperr::error(span, format!("litext: malformed float literal: {e}")))?;
        Ok(LitFloat::new(-value, span, suffix))
    }
}

// ---------------------------------------------------------------------------
// float impls
// ---------------------------------------------------------------------------

macro_rules! impl_from_lit_float {
    ($($t:ty),*) => {
        $(impl FromLit for $t {
            #[inline]
            fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
                Ok(LitFloat::<$t>::from_lit(lit)?.value)
            }
            #[inline]
            fn from_negative_lit(lit: Literal) -> Result<Self, TokenStream> {
                Ok(LitFloat::<$t>::from_negative_lit(lit)?.value)
            }
        })*
    };
}

impl_from_lit_float!(f32, f64);

// ---------------------------------------------------------------------------
// LitBool
// ---------------------------------------------------------------------------

/// A parsed boolean literal bundled with its source location.
///
/// `true` and `false` are identifier tokens in Rust's token stream, not literal
/// tokens. The [`FromLit`] implementation overrides [`FromLit::from_ident`] to handle
/// them. [`FromLit::from_lit`] always returns an error.
///
/// Use `LitBool` when you need the span. Use `bool` when you only need the value.
///
/// # Example
///
/// ```ignore
/// use litext::{litext, TokenStream};
/// use litext::literal::LitBool;
///
/// pub fn my_macro(input: TokenStream) -> TokenStream {
///     let lit: LitBool = litext!(input as LitBool);
///     if !lit.value() {
///         return comperr::error(lit.span(), "feature must be enabled");
///     }
///     quote::quote! { /* use lit.value() */ }
/// }
/// ```
pub struct LitBool {
    /// The parsed boolean value.
    pub value: bool,
    /// The source location of the literal.
    pub span: Span,
}

impl LitBool {
    /// Creates a new [`LitBool`] from a value and a span.
    #[must_use]
    pub fn new(value: bool, span: Span) -> Self {
        Self { value, span }
    }

    /// Returns the parsed boolean value.
    #[must_use]
    pub fn value(&self) -> bool {
        self.value
    }

    /// Returns the source span of the literal.
    #[must_use]
    pub fn span(&self) -> Span {
        self.span
    }
}

impl FromLit for LitBool {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        Err(comperr::error(
            lit.span(),
            "expected `true` or `false`, found a literal",
        ))
    }

    #[inline]
    fn from_ident(ident: Ident) -> Result<Self, TokenStream> {
        let span = ident.span();
        match ident.to_string().as_str() {
            "true" => Ok(LitBool::new(true, span)),
            "false" => Ok(LitBool::new(false, span)),
            other => Err(comperr::error(
                span,
                format!("expected `true` or `false`, found `{other}`"),
            )),
        }
    }
}

impl FromLit for bool {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        Err(comperr::error(
            lit.span(),
            "expected `true` or `false`, found a literal",
        ))
    }

    #[inline]
    fn from_ident(ident: Ident) -> Result<Self, TokenStream> {
        let span = ident.span();
        match ident.to_string().as_str() {
            "true" => Ok(true),
            "false" => Ok(false),
            other => Err(comperr::error(
                span,
                format!("expected `true` or `false`, found `{other}`"),
            )),
        }
    }
}

// ---------------------------------------------------------------------------
// LitChar
// ---------------------------------------------------------------------------

/// A parsed character literal bundled with its source location.
///
/// Escape sequences are resolved during extraction. The extracted [`value`](Self::value)
/// is always a single valid Unicode `char`.
///
/// # Supported Formats
///
/// | Format | Example |
/// |--------|---------|
/// | Regular character | `'a'`, `'z'` |
/// | Escape sequences | `'\n'`, `'\r'`, `'\t'`, `'\\'`, `'\''`, `'\"'`, `'\0'` |
/// | Hex escape | `'\x41'` (ASCII) |
/// | Unicode escape | `'\u{1F600}'` (emoji) |
///
/// The Rust tokenizer validates escape sequences before litext processes them.
///
/// # Example
///
/// ```ignore
/// use litext::{litext, TokenStream};
/// use litext::literal::LitChar;
///
/// pub fn my_macro(input: TokenStream) -> TokenStream {
///     let lit: LitChar = litext!(input as LitChar);
///     if lit.value().is_control() {
///         return comperr::error(lit.span(), "control characters not allowed");
///     }
///     quote::quote! { /* use lit.value() */ }
/// }
/// ```
pub struct LitChar {
    /// The parsed character value.
    pub value: char,
    /// The source location of the literal.
    pub span: Span,
}

impl LitChar {
    /// Creates a new [`LitChar`] from a value and a span.
    #[must_use]
    pub fn new(value: char, span: Span) -> Self {
        Self { value, span }
    }

    /// Returns the parsed character value.
    #[must_use]
    pub fn value(&self) -> char {
        self.value
    }

    /// Returns the source span of the literal.
    #[must_use]
    pub fn span(&self) -> Span {
        self.span
    }
}

impl FromLit for LitChar {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        let span = lit.span();
        let raw = lit.to_string();
        let Some(inner) = raw.strip_prefix('\'').and_then(|s| s.strip_suffix('\'')) else {
            return Err(comperr::error(span, "expected a char literal"));
        };
        let unescaped = crate::unescape(inner, span)?;
        if unescaped.chars().count() != 1 {
            return Err(comperr::error(span, "invalid char literal"));
        }
        // SAFETY: count() == 1 guarantees exactly one char exists
        Ok(LitChar::new(unescaped.chars().next().unwrap(), span))
    }
}

impl FromLit for char {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        Ok(LitChar::from_lit(lit)?.value)
    }
}

// ---------------------------------------------------------------------------
// C and Byte strings
// ---------------------------------------------------------------------------

use std::ffi::{CStr, CString};

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

/// Parses a byte string literal (`b"..."` or `br#"..."#`) into raw bytes.
///
/// Unlike string literal parsing, `\xNN` allows the full 0x00..=0xFF range.
fn parse_byte_str_raw(raw: &str, span: Span) -> Result<Vec<u8>, TokenStream> {
    if raw.starts_with("br") {
        let rest = &raw[1..];
        let inner = crate::parse_raw(rest)
            .ok_or_else(|| comperr::error(span, "litext: malformed raw byte string literal"))?;
        return Ok(inner.into_bytes());
    }

    if let Some(inner) = raw.strip_prefix("b\"").and_then(|s| s.strip_suffix('"')) {
        return crate::unescape_bytes(inner, span);
    }

    Err(comperr::error(
        span,
        "litext: expected a byte string literal",
    ))
}

/// Parses a C string literal (`c"..."` or `cr#"..."#`) into raw bytes, without
/// the null terminator (which `CString::new` appends). Interior null bytes cause
/// `CString::new` to fail, producing a compile error.
fn parse_c_str_raw(raw: &str, span: Span) -> Result<Vec<u8>, TokenStream> {
    if raw.starts_with("cr") {
        let rest = &raw[1..];
        let inner = crate::parse_raw(rest)
            .ok_or_else(|| comperr::error(span, "litext: malformed raw C string literal"))?;
        return Ok(inner.into_bytes());
    }

    if let Some(inner) = raw.strip_prefix("c\"").and_then(|s| s.strip_suffix('"')) {
        let unescaped = crate::unescape(inner, span)?;
        return Ok(unescaped.into_bytes());
    }

    Err(comperr::error(span, "litext: expected a C string literal"))
}

// ---------------------------------------------------------------------------
// LitByteStr
// ---------------------------------------------------------------------------

/// A parsed byte string literal (`b"..."` or `br#"..."#`) bundled with its source location.
///
/// Unlike string literals which restrict `\x` to ASCII (0x00..=0x7F), byte strings
/// allow the full 0x00..=0xFF range for `\x` escapes.
///
/// # Supported Formats
///
/// | Format | Example |
/// |--------|---------|
/// | Regular byte string | `b"hello"` |
/// | Byte string escapes | `b"\xff\x80"`, `b"\n\t\r\\"` |
/// | Raw byte string | `br#"raw bytes"#` |
///
/// # Example
///
/// ```ignore
/// use litext::{litext, TokenStream};
/// use litext::literal::LitByteStr;
///
/// pub fn my_macro(input: TokenStream) -> TokenStream {
///     let lit: LitByteStr = litext!(input as LitByteStr);
///     let bytes: &[u8] = lit.value();
/// }
/// ```
pub struct LitByteStr {
    /// The extracted bytes from the byte string literal.
    pub value: Vec<u8>,
    /// The source location of the literal.
    pub span: Span,
}

impl LitByteStr {
    /// Creates a new [`LitByteStr`] from a value and a span.
    #[must_use]
    pub fn new(value: Vec<u8>, span: Span) -> Self {
        Self { value, span }
    }

    /// Returns the extracted bytes.
    #[must_use]
    pub fn value(&self) -> &[u8] {
        &self.value
    }

    /// Returns the source span of the literal.
    #[must_use]
    pub fn span(&self) -> Span {
        self.span
    }
}

impl FromLit for LitByteStr {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        let span = lit.span();
        let raw = lit.to_string();
        let bytes = parse_byte_str_raw(&raw, span)?;
        Ok(LitByteStr::new(bytes, span))
    }
}

impl FromLit for Vec<u8> {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        Ok(LitByteStr::from_lit(lit)?.value)
    }
}

// ---------------------------------------------------------------------------
// LitByte
// ---------------------------------------------------------------------------

/// A parsed byte literal (`b'...'`) bundled with its source location.
///
/// The full 0x00..=0xFF byte range is valid. `\xNN` escapes with `NN > 7F`
/// are accepted, unlike in string literals where they are rejected.
///
/// | Input | Extracted value |
/// |-------|-----------------|
/// | `b'a'` | `97` |
/// | `b'\n'` | `10` |
/// | `b'\xff'` | `255` |
/// | `b'\x41'` | `65` |
///
/// # Example
///
/// ```ignore
/// use litext::{litext, TokenStream};
/// use litext::literal::LitByte;
///
/// pub fn my_macro(input: TokenStream) -> TokenStream {
///     let lit: LitByte = litext!(input as LitByte);
///     if lit.value() == 0 {
///         return comperr::error(lit.span(), "null bytes not allowed");
///     }
/// }
/// ```
pub struct LitByte {
    /// The extracted byte value.
    pub value: u8,
    /// The source location of the literal.
    pub span: Span,
}

impl LitByte {
    /// Creates a new [`LitByte`] from a value and a span.
    #[must_use]
    pub fn new(value: u8, span: Span) -> Self {
        Self { value, span }
    }

    /// Returns the extracted byte value.
    #[must_use]
    pub fn value(&self) -> u8 {
        self.value
    }

    /// Returns the source span of the literal.
    #[must_use]
    pub fn span(&self) -> Span {
        self.span
    }
}

impl FromLit for LitByte {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        let span = lit.span();
        let raw = lit.to_string();

        let Some(inner) = raw.strip_prefix("b'").and_then(|s| s.strip_suffix('\'')) else {
            return Err(comperr::error(span, "expected a byte literal"));
        };

        let bytes = crate::unescape_bytes(inner, span)?;

        if bytes.len() != 1 {
            return Err(comperr::error(span, "invalid byte literal"));
        }

        Ok(LitByte::new(bytes[0], span))
    }
}

// ---------------------------------------------------------------------------
// LitCStr
// ---------------------------------------------------------------------------

/// A parsed C string literal (`c"..."` or `cr#"..."#`) bundled with its source location.
///
/// The extracted value is a [`CString`] with the null terminator already appended.
/// Interior null bytes produce a compile error at extraction time.
///
/// # Supported Formats
///
/// | Format | Example |
/// |--------|---------|
/// | Regular C string | `c"hello"` |
/// | C string with escapes | `c"hello\nworld"` |
/// | Raw C string | `cr#"raw c string"#` |
///
/// # Example
///
/// ```ignore
/// use litext::{litext, TokenStream};
/// use litext::literal::LitCStr;
///
/// pub fn my_macro(input: TokenStream) -> TokenStream {
///     let lit: LitCStr = litext!(input as LitCStr);
///     let value: &std::ffi::CStr = lit.value();
/// }
/// ```
pub struct LitCStr {
    /// The extracted C string value.
    pub value: CString,
    /// The source location of the literal.
    pub span: Span,
}

impl LitCStr {
    /// Creates a new [`LitCStr`] from a value and a span.
    #[must_use]
    pub fn new(value: CString, span: Span) -> Self {
        Self { value, span }
    }

    /// Returns the extracted C string value.
    #[must_use]
    pub fn value(&self) -> &CStr {
        &self.value
    }

    /// Returns the source span of the literal.
    #[must_use]
    pub fn span(&self) -> Span {
        self.span
    }
}

impl FromLit for LitCStr {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        let span = lit.span();
        let raw = lit.to_string();
        let bytes = parse_c_str_raw(&raw, span)?;
        let cstring = CString::new(bytes).map_err(|_| {
            comperr::error(
                span,
                "litext: C string literal contains an interior null byte",
            )
        })?;
        Ok(LitCStr::new(cstring, span))
    }
}

impl FromLit for CString {
    #[inline]
    fn from_lit(lit: Literal) -> Result<Self, TokenStream> {
        Ok(LitCStr::from_lit(lit)?.value)
    }
}