struson 0.7.2

//! Integration test for a custom `JsonWriter` implementation
//!
//! The `JsonWriter` implementation here is built on top of serde_json's `Value`.
//! This ensures that the `JsonWriter` trait can be implemented by users, and does
//! not depend on something which is only accessible within Struson.
//!
//! **Important:** This code is only for integration test and demonstration purposes;
//! it is not intended to be used in production code.

use custom_writer::JsonValueWriter;
use serde_json::json;
use std::io::Write;
use struson::{
    reader::{JsonReader, JsonStreamReader},
    writer::{JsonNumberError, JsonWriter, StringValueWriter},
};

mod custom_writer {
    use serde_json::{Map, Number, Value};
    use std::io::{ErrorKind, Write};
    use struson::writer::{
        FiniteNumber, FloatingPointNumber, JsonNumberError, JsonWriter, StringValueWriter,
    };

    type IoError = std::io::Error;

    enum StackValue {
        Array(Vec<Value>),
        Object(Map<String, Value>),
    }

    pub struct JsonValueWriter {
        stack: Vec<StackValue>,
        pending_name: Option<String>,
        is_string_value_writer_active: bool,
        /// Holds the final value until `finish_document` is called
        final_value: Option<Value>,
    }
    impl JsonValueWriter {
        pub fn new() -> Self {
            JsonValueWriter {
                stack: Vec::new(),
                pending_name: None,
                is_string_value_writer_active: false,
                final_value: None,
            }
        }
    }

    impl JsonValueWriter {
        fn verify_string_writer_inactive(&self) {
            if self.is_string_value_writer_active {
                panic!("Incorrect writer usage: String value writer is active");
            }
        }

        fn check_before_value(&self) {
            self.verify_string_writer_inactive();
            if self.final_value.is_some() {
                panic!("Incorrect writer usage: Top-level value has already been written")
            }
            if let Some(StackValue::Object(_)) = self.stack.last() {
                if self.pending_name.is_none() {
                    panic!("Incorrect writer usage: Member name is expected");
                }
            }
        }

        fn add_value(&mut self, value: Value) {
            if let Some(stack_value) = self.stack.last_mut() {
                match stack_value {
                    StackValue::Array(array) => array.push(value),
                    StackValue::Object(object) => {
                        object.insert(self.pending_name.take().unwrap(), value);
                    }
                };
            } else {
                debug_assert!(
                    self.final_value.is_none(),
                    "caller should have verified that final value is not set yet"
                );
                self.final_value = Some(value);
            }
        }
    }

    fn serde_number_from_f64(f: f64) -> Result<Number, JsonNumberError> {
        Number::from_f64(f)
            .ok_or_else(|| JsonNumberError::InvalidNumber(format!("non-finite number: {f}")))
    }

    impl JsonWriter for JsonValueWriter {
        type WriterResult = Value;

        fn begin_object(&mut self) -> Result<(), IoError> {
            self.check_before_value();
            self.stack.push(StackValue::Object(Map::new()));
            Ok(())
        }

        fn end_object(&mut self) -> Result<(), IoError> {
            self.verify_string_writer_inactive();
            if let Some(StackValue::Object(map)) = self.stack.pop() {
                self.add_value(Value::Object(map));
                Ok(())
            } else {
                panic!("Incorrect writer usage: Cannot end object; not inside object");
            }
        }

        fn begin_array(&mut self) -> Result<(), IoError> {
            self.check_before_value();
            self.stack.push(StackValue::Array(Vec::new()));
            Ok(())
        }

        fn end_array(&mut self) -> Result<(), IoError> {
            self.verify_string_writer_inactive();
            if let Some(StackValue::Array(vec)) = self.stack.pop() {
                self.add_value(Value::Array(vec));
                Ok(())
            } else {
                panic!("Incorrect writer usage: Cannot end array; not inside array");
            }
        }

        fn name(&mut self, name: &str) -> Result<(), IoError> {
            self.verify_string_writer_inactive();
            if let Some(StackValue::Object(_)) = self.stack.last() {
                if self.pending_name.is_some() {
                    panic!(
                        "Incorrect writer usage: Member name has already been written; expecting value"
                    );
                }
                self.pending_name = Some(name.to_owned());
                Ok(())
            } else {
                panic!("Incorrect writer usage: Cannot write name; not inside object");
            }
        }

        fn null_value(&mut self) -> Result<(), IoError> {
            self.check_before_value();
            self.add_value(Value::Null);
            Ok(())
        }

        fn bool_value(&mut self, value: bool) -> Result<(), IoError> {
            self.check_before_value();
            self.add_value(Value::Bool(value));
            Ok(())
        }

        fn string_value(&mut self, value: &str) -> Result<(), IoError> {
            self.check_before_value();
            self.add_value(Value::String(value.to_owned()));
            Ok(())
        }

        fn string_value_writer(&mut self) -> Result<impl StringValueWriter + '_, IoError> {
            self.check_before_value();
            self.is_string_value_writer_active = true;
            Ok(StringValueWriterImpl {
                buf: Vec::new(),
                json_writer: self,
            })
        }

        fn number_value_from_string(&mut self, value: &str) -> Result<(), JsonNumberError> {
            self.check_before_value();
            // TODO: `parse::<f64>` might not match JSON number string format (might allow more / less than allowed by JSON)?
            let f = value
                .parse::<f64>()
                .map_err(|e| JsonNumberError::InvalidNumber(e.to_string()))?;
            self.add_value(Value::Number(serde_number_from_f64(f)?));
            Ok(())
        }

        fn number_value<N: FiniteNumber>(&mut self, value: N) -> Result<(), IoError> {
            let number = value
                .as_u64()
                .map(Number::from)
                .or_else(|| value.as_i64().map(Number::from));

            if let Some(n) = number {
                self.check_before_value();
                self.add_value(Value::Number(n));
                Ok(())
            } else {
                value.use_json_number(|number_str| {
                    self.number_value_from_string(number_str)
                        .map_err(|e| match e {
                            JsonNumberError::InvalidNumber(e) => {
                                panic!(
                                    "Unexpected: Writer rejected finite number '{number_str}': {e}"
                                )
                            }
                            JsonNumberError::IoError(e) => IoError::other(e),
                        })
                })
            }
        }

        fn fp_number_value<N: FloatingPointNumber>(
            &mut self,
            value: N,
        ) -> Result<(), JsonNumberError> {
            let number = if let Some(n) = value.as_f64() {
                Some(serde_number_from_f64(n)?)
            } else {
                None
            };

            if let Some(n) = number {
                self.check_before_value();
                self.add_value(Value::Number(n));
                Ok(())
            } else {
                // TODO: Cannot match over possible implementations? Therefore have to use string representation
                value.use_json_number(|number_str| {
                    self.number_value_from_string(number_str).map_err(|e| {
                        match e {
                            // `use_json_number` should have verified that value is valid finite JSON number
                            JsonNumberError::InvalidNumber(e) => {
                                panic!(
                                    "Unexpected: Writer rejected finite number '{number_str}': {e}"
                                )
                            }
                            JsonNumberError::IoError(e) => IoError::other(e),
                        }
                    })
                })
            }
        }

        #[cfg(feature = "serde")]
        fn serialize_value<S: serde_core::Serialize>(
            &mut self,
            value: &S,
        ) -> Result<(), struson::serde::SerializerError> {
            self.check_before_value();
            let mut serializer = struson::serde::JsonWriterSerializer::new(self);
            value.serialize(&mut serializer)
            // TODO: Verify that value was properly serialized (only single value; no incomplete array or object)
            // might not be necessary because Serde's Serialize API enforces this
        }

        fn finish_document(self) -> Result<Self::WriterResult, IoError> {
            self.verify_string_writer_inactive();
            if let Some(value) = self.final_value {
                Ok(value)
            } else {
                panic!("Incorrect writer usage: Top-level value is incomplete")
            }
        }
    }

    struct StringValueWriterImpl<'j> {
        buf: Vec<u8>,
        json_writer: &'j mut JsonValueWriter,
    }
    impl Write for StringValueWriterImpl<'_> {
        fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
            self.buf.extend_from_slice(buf);
            Ok(buf.len())
        }

        fn flush(&mut self) -> std::io::Result<()> {
            // No-op
            Ok(())
        }
    }
    impl StringValueWriter for StringValueWriterImpl<'_> {
        fn finish_value(self) -> Result<(), IoError> {
            let string =
                String::from_utf8(self.buf).map_err(|e| IoError::new(ErrorKind::InvalidData, e))?;
            self.json_writer.add_value(Value::String(string));
            self.json_writer.is_string_value_writer_active = false;
            Ok(())
        }
    }
}

#[test]
fn write() -> Result<(), Box<dyn std::error::Error>> {
    fn assert_invalid_number(expected_message: Option<&str>, result: Result<(), JsonNumberError>) {
        match result {
            Err(JsonNumberError::InvalidNumber(message)) => {
                if let Some(expected_message) = expected_message {
                    assert_eq!(expected_message, message)
                }
            }
            _ => panic!("Unexpected result: {result:?}"),
        }
    }

    let mut json_writer = JsonValueWriter::new();

    json_writer.begin_array()?;

    json_writer.begin_object()?;
    json_writer.name("name1")?;
    json_writer.begin_array()?;
    json_writer.bool_value(true)?;
    json_writer.end_array()?;
    json_writer.name("name2")?;
    json_writer.bool_value(false)?;
    json_writer.end_object()?;

    json_writer.null_value()?;
    json_writer.bool_value(true)?;
    json_writer.bool_value(false)?;
    json_writer.string_value("string")?;

    let mut string_writer = json_writer.string_value_writer()?;
    string_writer.write_all("first ".as_bytes())?;
    string_writer.write_all("second".as_bytes())?;
    string_writer.finish_value()?;

    json_writer.number_value_from_string("123")?;
    assert_invalid_number(
        Some(&format!("non-finite number: {}", f64::INFINITY)),
        json_writer.number_value_from_string("Infinity"),
    );
    // Don't check for exact error message because it is created by Rust and might change in the future
    assert_invalid_number(None, json_writer.number_value_from_string("test"));
    json_writer.number_value(45)?;
    json_writer.number_value(-67)?;
    json_writer.fp_number_value(8.9)?;
    assert_invalid_number(
        Some(&format!("non-finite number: {}", f64::INFINITY)),
        json_writer.fp_number_value(f64::INFINITY),
    );

    json_writer.end_array()?;
    let written_value = json_writer.finish_document()?;

    let expected_json = json!([
        {
            "name1": [true],
            "name2": false,
        },
        null,
        true,
        false,
        "string",
        "first second",
        // Current number from string implementation always writes f64
        123.0,
        45,
        -67,
        8.9,
    ]);
    assert_eq!(expected_json, written_value);

    Ok(())
}

#[test]
fn transfer() -> Result<(), Box<dyn std::error::Error>> {
    let mut json_writer = JsonValueWriter::new();

    let mut json_reader = JsonStreamReader::new(
        "[true, 123, {\"name1\": \"value1\", \"name2\": null}, false]".as_bytes(),
    );
    json_reader.transfer_to(&mut json_writer)?;
    json_reader.consume_trailing_whitespace()?;

    let written_value = json_writer.finish_document()?;

    let expected_json = json!([
        true,
        // Current number from string implementation always writes f64
        123.0,
        {
            "name1": "value1",
            "name2": null,
        },
        false,
    ]);
    assert_eq!(expected_json, written_value);

    Ok(())
}

#[cfg(feature = "serde")]
#[test]
fn serialize() -> Result<(), Box<dyn std::error::Error>> {
    use serde::Serialize;

    #[derive(Serialize)]
    struct CustomStruct {
        a: u32,
        b: &'static str,
    }

    let mut json_writer = JsonValueWriter::new();
    json_writer.serialize_value(&CustomStruct { a: 123, b: "test" })?;
    let written_value = json_writer.finish_document()?;

    let expected_json = json!({
        "a": 123,
        "b": "test",
    });
    assert_eq!(expected_json, written_value);

    Ok(())
}