serde-libconfigasaurus 0.3.0

//! Serializer for libconfig format

use serde::{Serialize, ser};

use crate::error::{Error, Result};

/// A structure for serializing Rust values into libconfig format
pub struct Serializer {
    output: String,
    indent_level: usize,
    indent_size: usize,
}

impl Serializer {
    fn new() -> Self {
        Serializer {
            output: String::new(),
            indent_level: 0,
            indent_size: 2,
        }
    }

    fn indent(&mut self) {
        self.indent_level += 1;
    }

    fn dedent(&mut self) {
        self.indent_level = self.indent_level.saturating_sub(1);
    }

    fn write_indent(&mut self) {
        for _ in 0..(self.indent_level * self.indent_size) {
            self.output.push(' ');
        }
    }
}

/// Serialize the given value into a libconfig string
pub fn to_string<T>(value: &T) -> Result<String>
where
    T: Serialize,
{
    let mut serializer = Serializer::new();
    value.serialize(&mut serializer)?;
    Ok(serializer.output)
}

impl<'a> ser::Serializer for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    type SerializeSeq = Self;
    type SerializeTuple = Self;
    type SerializeTupleStruct = Self;
    type SerializeTupleVariant = Self;
    type SerializeMap = Self;
    type SerializeStruct = Self;
    type SerializeStructVariant = Self;

    fn serialize_bool(self, v: bool) -> Result<()> {
        self.output += if v { "true" } else { "false" };
        Ok(())
    }

    fn serialize_i8(self, v: i8) -> Result<()> {
        self.serialize_i32(i32::from(v))
    }

    fn serialize_i16(self, v: i16) -> Result<()> {
        self.serialize_i32(i32::from(v))
    }

    fn serialize_i32(self, v: i32) -> Result<()> {
        self.output += &v.to_string();
        Ok(())
    }

    fn serialize_i64(self, v: i64) -> Result<()> {
        self.output += &v.to_string();
        self.output += "L";
        Ok(())
    }

    fn serialize_u8(self, v: u8) -> Result<()> {
        self.serialize_u32(u32::from(v))
    }

    fn serialize_u16(self, v: u16) -> Result<()> {
        self.serialize_u32(u32::from(v))
    }

    fn serialize_u32(self, v: u32) -> Result<()> {
        self.output += &v.to_string();
        Ok(())
    }

    fn serialize_u64(self, v: u64) -> Result<()> {
        self.output += &v.to_string();
        self.output += "L";
        Ok(())
    }

    fn serialize_f32(self, v: f32) -> Result<()> {
        self.serialize_f64(f64::from(v))
    }

    fn serialize_f64(self, v: f64) -> Result<()> {
        let s = v.to_string();
        self.output += &s;
        // Ensure float always has a decimal point to distinguish from integer
        if !s.contains('.') && !s.contains('e') && !s.contains('E') {
            self.output += ".0";
        }
        Ok(())
    }

    fn serialize_char(self, v: char) -> Result<()> {
        self.serialize_str(&v.to_string())
    }

    fn serialize_str(self, v: &str) -> Result<()> {
        self.output.push('"');
        for ch in v.chars() {
            match ch {
                '"' => self.output.push_str("\\\""),
                '\\' => self.output.push_str("\\\\"),
                '\n' => self.output.push_str("\\n"),
                '\r' => self.output.push_str("\\r"),
                '\t' => self.output.push_str("\\t"),
                '\x0C' => self.output.push_str("\\f"),
                '\x08' => self.output.push_str("\\b"),
                '\x0B' => self.output.push_str("\\v"),
                '\x07' => self.output.push_str("\\a"),
                _ => self.output.push(ch),
            }
        }
        self.output.push('"');
        Ok(())
    }

    fn serialize_bytes(self, v: &[u8]) -> Result<()> {
        use ser::SerializeSeq;
        let mut seq = self.serialize_seq(Some(v.len()))?;
        for byte in v {
            seq.serialize_element(byte)?;
        }
        seq.end()
    }

    fn serialize_none(self) -> Result<()> {
        Err(Error::TypeNotSupported("Option::None".to_string()))
    }

    fn serialize_some<T>(self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(self)
    }

    fn serialize_unit(self) -> Result<()> {
        Err(Error::UnitNotSupported)
    }

    fn serialize_unit_struct(self, _name: &'static str) -> Result<()> {
        self.serialize_unit()
    }

    fn serialize_unit_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
    ) -> Result<()> {
        self.serialize_str(variant)
    }

    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(self)
    }

    fn serialize_newtype_variant<T>(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        value: &T,
    ) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        self.output += variant;
        self.output += " = ";
        value.serialize(&mut *self)?;
        Ok(())
    }

    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq> {
        self.output.push('[');
        Ok(self)
    }

    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple> {
        self.output.push('(');
        Ok(self)
    }

    fn serialize_tuple_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleStruct> {
        self.output.push('(');
        Ok(self)
    }

    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleVariant> {
        self.output += variant;
        self.output += " = (";
        Ok(self)
    }

    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap> {
        self.output.push('{');
        self.indent();
        Ok(self)
    }

    fn serialize_struct(self, _name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
        self.serialize_map(Some(len))
    }

    fn serialize_struct_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStructVariant> {
        self.output += variant;
        self.output += " = {";
        self.indent();
        Ok(self)
    }
}

impl<'a> ser::SerializeSeq for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if !self.output.ends_with('[') {
            self.output += ", ";
        }
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.output.push(']');
        Ok(())
    }
}

impl<'a> ser::SerializeTuple for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if !self.output.ends_with('(') {
            self.output += ", ";
        }
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.output.push(')');
        Ok(())
    }
}

impl<'a> ser::SerializeTupleStruct for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if !self.output.ends_with('(') {
            self.output += ", ";
        }
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.output.push(')');
        Ok(())
    }
}

impl<'a> ser::SerializeTupleVariant for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if !self.output.ends_with('(') {
            self.output += ", ";
        }
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.output.push(')');
        Ok(())
    }
}

impl<'a> ser::SerializeMap for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_key<T>(&mut self, key: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if !self.output.ends_with('{') {
            self.output.push(';');
        }
        self.output.push('\n');
        self.write_indent();
        // Validate key is a string, then write as bare identifier (not quoted)
        let mut key_capture = KeyCapture { key: String::new() };
        key.serialize(&mut key_capture)?;
        self.output += &key_capture.key;
        Ok(())
    }

    fn serialize_value<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        self.output += " = ";
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.dedent();
        if !self.output.ends_with('{') {
            self.output.push(';');
        }
        self.output.push('\n');
        self.write_indent();
        self.output.push('}');
        Ok(())
    }
}

impl<'a> ser::SerializeStruct for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if !self.output.ends_with('{') {
            self.output.push(';');
        }
        self.output.push('\n');
        self.write_indent();
        self.output += key;
        self.output += " = ";
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.dedent();
        if !self.output.ends_with('{') {
            self.output.push(';');
        }
        self.output.push('\n');
        self.write_indent();
        self.output.push('}');
        Ok(())
    }
}

impl<'a> ser::SerializeStructVariant for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if !self.output.ends_with('{') {
            self.output.push(';');
        }
        self.output.push('\n');
        self.write_indent();
        self.output += key;
        self.output += " = ";
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.dedent();
        if !self.output.ends_with('{') {
            self.output.push(';');
        }
        self.output.push('\n');
        self.write_indent();
        self.output.push('}');
        Ok(())
    }
}

// Helper serializer to capture map keys as bare identifier strings
struct KeyCapture {
    key: String,
}

impl<'a> ser::Serializer for &'a mut KeyCapture {
    type Ok = ();
    type Error = Error;

    type SerializeSeq = ser::Impossible<(), Error>;
    type SerializeTuple = ser::Impossible<(), Error>;
    type SerializeTupleStruct = ser::Impossible<(), Error>;
    type SerializeTupleVariant = ser::Impossible<(), Error>;
    type SerializeMap = ser::Impossible<(), Error>;
    type SerializeStruct = ser::Impossible<(), Error>;
    type SerializeStructVariant = ser::Impossible<(), Error>;

    fn serialize_str(self, v: &str) -> Result<()> {
        self.key = v.to_string();
        Ok(())
    }

    fn serialize_unit_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
    ) -> Result<()> {
        self.key = variant.to_string();
        Ok(())
    }

    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(self)
    }

    fn serialize_bool(self, _v: bool) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_i8(self, _v: i8) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_i16(self, _v: i16) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_i32(self, _v: i32) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_i64(self, _v: i64) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_u8(self, _v: u8) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_u16(self, _v: u16) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_u32(self, _v: u32) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_u64(self, _v: u64) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_f32(self, _v: f32) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_f64(self, _v: f64) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_char(self, _v: char) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_bytes(self, _v: &[u8]) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_none(self) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_some<T>(self, _value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_unit(self) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_unit_struct(self, _name: &'static str) -> Result<()> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_newtype_variant<T>(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _value: &T,
    ) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_tuple_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleStruct> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleVariant> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_struct(self, _name: &'static str, _len: usize) -> Result<Self::SerializeStruct> {
        Err(Error::KeyMustBeAString)
    }

    fn serialize_struct_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStructVariant> {
        Err(Error::KeyMustBeAString)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde::Serialize;

    #[test]
    fn test_serialize_primitives() {
        assert_eq!(to_string(&42u32).unwrap(), "42");
        assert_eq!(to_string(&42i64).unwrap(), "42L");
        assert_eq!(to_string(&3.14f64).unwrap(), "3.14");
        assert_eq!(to_string(&true).unwrap(), "true");
        assert_eq!(to_string(&"hello".to_string()).unwrap(), "\"hello\"");
    }

    #[test]
    fn test_serialize_array() {
        let arr = vec![1, 2, 3];
        assert_eq!(to_string(&arr).unwrap(), "[1, 2, 3]");
    }

    #[test]
    fn test_serialize_struct() {
        #[derive(Serialize)]
        struct Test {
            a: i32,
            b: String,
        }

        let test = Test {
            a: 42,
            b: "hello".to_string(),
        };
        let result = to_string(&test).unwrap();
        assert!(result.contains("a = 42"));
        assert!(result.contains("b = \"hello\""));
    }

    #[test]
    fn test_serialize_i8_no_l_suffix() {
        assert_eq!(to_string(&42i8).unwrap(), "42");
        assert_eq!(to_string(&42i16).unwrap(), "42");
        assert_eq!(to_string(&42i32).unwrap(), "42");
        assert_eq!(to_string(&42i64).unwrap(), "42L");
    }

    #[test]
    fn test_serialize_u64_has_l_suffix() {
        assert_eq!(to_string(&42u8).unwrap(), "42");
        assert_eq!(to_string(&42u16).unwrap(), "42");
        assert_eq!(to_string(&42u32).unwrap(), "42");
        assert_eq!(to_string(&42u64).unwrap(), "42L");
    }

    #[test]
    fn test_serialize_float_always_has_decimal() {
        // 1.0f64.to_string() is "1" in Rust - we must add ".0"
        assert_eq!(to_string(&1.0f64).unwrap(), "1.0");
        assert_eq!(to_string(&0.0f64).unwrap(), "0.0");
        // Already has decimal
        assert_eq!(to_string(&3.14f64).unwrap(), "3.14");
    }

    #[test]
    fn test_serialize_tuple_as_list() {
        let tup = (1, 2, 3);
        assert_eq!(to_string(&tup).unwrap(), "(1, 2, 3)");
    }

    #[test]
    fn test_serialize_map_bare_keys() {
        use indexmap::IndexMap;
        let mut map = IndexMap::new();
        map.insert("key".to_string(), 42i32);
        let result = to_string(&map).unwrap();
        // Keys should be bare identifiers, not quoted
        assert!(result.contains("key = 42"));
        assert!(!result.contains("\"key\""));
    }
}