parquet_variant_json/

from_json.rs

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

//! Module for parsing JSON strings as Variant

use arrow_schema::ArrowError;
use parquet_variant::{ObjectFieldBuilder, Variant, VariantBuilderExt};
use serde_json::{Number, Value};

/// Converts a JSON string to Variant using a [`VariantBuilderExt`], such as
/// [`VariantBuilder`].
///
/// The resulting `value` and `metadata` buffers can be
/// extracted using `builder.finish()`
///
/// # Arguments
/// * `json` - The JSON string to parse as Variant.
///
/// # Returns
///
/// * `Ok(())` if successful
/// * `Err` with error details if the conversion fails
///
/// [`VariantBuilder`]: parquet_variant::VariantBuilder
///
/// ```rust
/// # use parquet_variant::VariantBuilder;
/// # use parquet_variant_json::{JsonToVariant, VariantToJson};
///
/// let mut variant_builder = VariantBuilder::new();
/// let person_string = "{\"name\":\"Alice\", \"age\":30, ".to_string()
/// + "\"email\":\"alice@example.com\", \"is_active\": true, \"score\": 95.7,"
/// + "\"additional_info\": null}";
/// variant_builder.append_json(&person_string)?;
///
/// let (metadata, value) = variant_builder.finish();
///
/// let variant = parquet_variant::Variant::try_new(&metadata, &value)?;
///
/// let json_result = variant.to_json_string()?;
/// let json_value = variant.to_json_value()?;
///
/// let mut buffer = Vec::new();
/// variant.to_json(&mut buffer)?;
/// let buffer_result = String::from_utf8(buffer)?;
/// assert_eq!(json_result, "{\"additional_info\":null,\"age\":30,".to_string() +
/// "\"email\":\"alice@example.com\",\"is_active\":true,\"name\":\"Alice\",\"score\":95.7}");
/// assert_eq!(json_result, buffer_result);
/// assert_eq!(json_result, serde_json::to_string(&json_value)?);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub trait JsonToVariant {
    /// Create a Variant from a JSON string
    fn append_json(&mut self, json: &str) -> Result<(), ArrowError>;
}

impl<T: VariantBuilderExt> JsonToVariant for T {
    fn append_json(&mut self, json: &str) -> Result<(), ArrowError> {
        let json: Value = serde_json::from_str(json)
            .map_err(|e| ArrowError::InvalidArgumentError(format!("JSON format error: {e}")))?;

        append_json(&json, self)?;
        Ok(())
    }
}

fn variant_from_number<'m, 'v>(n: &Number) -> Result<Variant<'m, 'v>, ArrowError> {
    if let Some(i) = n.as_i64() {
        // Find minimum Integer width to fit
        if i as i8 as i64 == i {
            Ok((i as i8).into())
        } else if i as i16 as i64 == i {
            Ok((i as i16).into())
        } else if i as i32 as i64 == i {
            Ok((i as i32).into())
        } else {
            Ok(i.into())
        }
    } else {
        // Todo: Try decimal once we implement custom JSON parsing where we have access to strings
        // Try double - currently json_to_variant does not produce decimal
        match n.as_f64() {
            Some(f) => return Ok(f.into()),
            None => Err(ArrowError::InvalidArgumentError(format!(
                "Failed to parse {n} as number",
            ))),
        }?
    }
}

fn append_json(json: &Value, builder: &mut impl VariantBuilderExt) -> Result<(), ArrowError> {
    match json {
        Value::Null => builder.append_value(Variant::Null),
        Value::Bool(b) => builder.append_value(*b),
        Value::Number(n) => {
            builder.append_value(variant_from_number(n)?);
        }
        Value::String(s) => builder.append_value(s.as_str()),
        Value::Array(arr) => {
            let mut list_builder = builder.try_new_list()?;
            for val in arr {
                append_json(val, &mut list_builder)?;
            }
            list_builder.finish();
        }
        Value::Object(obj) => {
            let mut obj_builder = builder.try_new_object()?;
            for (key, value) in obj.iter() {
                let mut field_builder = ObjectFieldBuilder::new(key, &mut obj_builder);
                append_json(value, &mut field_builder)?;
            }
            obj_builder.finish();
        }
    };
    Ok(())
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::VariantToJson;
    use arrow_schema::ArrowError;
    use parquet_variant::{
        ShortString, Variant, VariantBuilder, VariantDecimal4, VariantDecimal8, VariantDecimal16,
    };

    struct JsonToVariantTest<'a> {
        json: &'a str,
        expected: Variant<'a, 'a>,
    }

    impl JsonToVariantTest<'_> {
        fn run(self) -> Result<(), ArrowError> {
            let mut variant_builder = VariantBuilder::new();
            variant_builder.append_json(self.json)?;
            let (metadata, value) = variant_builder.finish();
            let variant = Variant::try_new(&metadata, &value)?;
            assert_eq!(variant, self.expected);
            Ok(())
        }
    }

    #[test]
    fn test_json_to_variant_null() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "null",
            expected: Variant::Null,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_boolean_true() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "true",
            expected: Variant::BooleanTrue,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_boolean_false() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "false",
            expected: Variant::BooleanFalse,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_int8_positive() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "  127 ",
            expected: Variant::Int8(127),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_int8_negative() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "  -128 ",
            expected: Variant::Int8(-128),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_int16() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "  27134  ",
            expected: Variant::Int16(27134),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_int32() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: " -32767431  ",
            expected: Variant::Int32(-32767431),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_int64() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "92842754201389",
            expected: Variant::Int64(92842754201389),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal4_basic() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "1.23",
            expected: Variant::from(VariantDecimal4::try_new(123, 2)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal4_large_positive() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "99999999.9",
            expected: Variant::from(VariantDecimal4::try_new(999999999, 1)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal4_large_negative() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "-99999999.9",
            expected: Variant::from(VariantDecimal4::try_new(-999999999, 1)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal4_small_positive() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "0.999999999",
            expected: Variant::from(VariantDecimal4::try_new(999999999, 9)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal4_tiny_positive() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "0.000000001",
            expected: Variant::from(VariantDecimal4::try_new(1, 9)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal4_small_negative() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "-0.999999999",
            expected: Variant::from(VariantDecimal4::try_new(-999999999, 9)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal8_positive() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "999999999.0",
            expected: Variant::from(VariantDecimal8::try_new(9999999990, 1)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal8_negative() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "-999999999.0",
            expected: Variant::from(VariantDecimal8::try_new(-9999999990, 1)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal8_high_precision() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "0.999999999999999999",
            expected: Variant::from(VariantDecimal8::try_new(999999999999999999, 18)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal8_large_with_scale() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "9999999999999999.99",
            expected: Variant::from(VariantDecimal8::try_new(999999999999999999, 2)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal8_large_negative_with_scale() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "-9999999999999999.99",
            expected: Variant::from(VariantDecimal8::try_new(-999999999999999999, 2)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal16_large_integer() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "9999999999999999999", // integer larger than i64
            expected: Variant::from(VariantDecimal16::try_new(9999999999999999999, 0)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal16_high_precision() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "0.9999999999999999999",
            expected: Variant::from(VariantDecimal16::try_new(9999999999999999999, 19)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal16_max_value() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "79228162514264337593543950335", // 2 ^ 96 - 1
            expected: Variant::from(VariantDecimal16::try_new(79228162514264337593543950335, 0)?),
        }
        .run()
    }

    #[ignore]
    #[test]
    fn test_json_to_variant_decimal16_max_scale() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "7.9228162514264337593543950335", // using scale higher than this falls into double
            // since the max scale is 28.
            expected: Variant::from(VariantDecimal16::try_new(
                79228162514264337593543950335,
                28,
            )?),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_double_precision() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "0.79228162514264337593543950335",
            expected: Variant::Double(0.792_281_625_142_643_4_f64),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_double_scientific_positive() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "15e-1",
            expected: Variant::Double(15e-1f64),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_double_scientific_negative() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "-15e-1",
            expected: Variant::Double(-15e-1f64),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_short_string() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: "\"harsh\"",
            expected: Variant::ShortString(ShortString::try_new("harsh")?),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_short_string_max_length() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: &format!("\"{}\"", "a".repeat(63)),
            expected: Variant::ShortString(ShortString::try_new(&"a".repeat(63))?),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_long_string() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: &format!("\"{}\"", "a".repeat(64)),
            expected: Variant::String(&"a".repeat(64)),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_very_long_string() -> Result<(), ArrowError> {
        JsonToVariantTest {
            json: &format!("\"{}\"", "b".repeat(100000)),
            expected: Variant::String(&"b".repeat(100000)),
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_array_simple() -> Result<(), ArrowError> {
        let mut variant_builder = VariantBuilder::new();
        let mut list_builder = variant_builder.new_list();
        list_builder.append_value(Variant::Int8(127));
        list_builder.append_value(Variant::Int16(128));
        list_builder.append_value(Variant::Int32(-32767431));
        list_builder.finish();
        let (metadata, value) = variant_builder.finish();
        let variant = Variant::try_new(&metadata, &value)?;

        JsonToVariantTest {
            json: "[127, 128, -32767431]",
            expected: variant,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_array_with_object() -> Result<(), ArrowError> {
        let mut variant_builder = VariantBuilder::new();
        let mut list_builder = variant_builder.new_list();
        let mut object_builder_inner = list_builder.new_object();
        object_builder_inner.insert("age", Variant::Int8(32));
        object_builder_inner.finish();
        list_builder.append_value(Variant::Int16(128));
        list_builder.append_value(Variant::BooleanFalse);
        list_builder.finish();
        let (metadata, value) = variant_builder.finish();
        let variant = Variant::try_new(&metadata, &value)?;

        JsonToVariantTest {
            json: "[{\"age\": 32}, 128, false]",
            expected: variant,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_array_large_u16_offset() -> Result<(), ArrowError> {
        // u16 offset - 128 i8's + 1 "true" = 257 bytes
        let mut variant_builder = VariantBuilder::new();
        let mut list_builder = variant_builder.new_list();
        for _ in 0..128 {
            list_builder.append_value(Variant::Int8(1));
        }
        list_builder.append_value(Variant::BooleanTrue);
        list_builder.finish();
        let (metadata, value) = variant_builder.finish();
        let variant = Variant::try_new(&metadata, &value)?;

        JsonToVariantTest {
            json: &format!("[{} true]", "1, ".repeat(128)),
            expected: variant,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_array_nested_large() -> Result<(), ArrowError> {
        // verify u24, and large_size
        let mut variant_builder = VariantBuilder::new();
        let mut list_builder = variant_builder.new_list();
        for _ in 0..256 {
            let mut list_builder_inner = list_builder.new_list();
            for _ in 0..255 {
                list_builder_inner.append_value(Variant::Null);
            }
            list_builder_inner.finish();
        }
        list_builder.finish();
        let (metadata, value) = variant_builder.finish();
        let variant = Variant::try_new(&metadata, &value)?;
        let intermediate = format!("[{}]", vec!["null"; 255].join(", "));
        let json = format!("[{}]", vec![intermediate; 256].join(", "));
        JsonToVariantTest {
            json: json.as_str(),
            expected: variant,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_object_simple() -> Result<(), ArrowError> {
        let mut variant_builder = VariantBuilder::new();
        let mut object_builder = variant_builder.new_object();
        object_builder.insert("a", Variant::Int8(3));
        object_builder.insert("b", Variant::Int8(2));
        object_builder.finish();
        let (metadata, value) = variant_builder.finish();
        let variant = Variant::try_new(&metadata, &value)?;
        JsonToVariantTest {
            json: "{\"b\": 2, \"a\": 1, \"a\": 3}",
            expected: variant,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_object_complex() -> Result<(), ArrowError> {
        let mut variant_builder = VariantBuilder::new();
        let mut object_builder = variant_builder.new_object();
        let mut inner_list_builder = object_builder.new_list("booleans");
        inner_list_builder.append_value(Variant::BooleanTrue);
        inner_list_builder.append_value(Variant::BooleanFalse);
        inner_list_builder.finish();
        object_builder.insert("null", Variant::Null);
        let mut inner_list_builder = object_builder.new_list("numbers");
        inner_list_builder.append_value(Variant::Int8(4));
        inner_list_builder.append_value(Variant::Double(-3e0));
        inner_list_builder.append_value(Variant::Double(1001e-3));
        inner_list_builder.finish();
        object_builder.finish();
        let (metadata, value) = variant_builder.finish();
        let variant = Variant::try_new(&metadata, &value)?;
        JsonToVariantTest {
            json: "{\"numbers\": [4, -3e0, 1001e-3], \"null\": null, \"booleans\": [true, false]}",
            expected: variant,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_object_very_large() -> Result<(), ArrowError> {
        // 256 elements (keys: 000-255) - each element is an object of 256 elements (240-495) - each
        // element a list of numbers from 0-127
        let keys: Vec<String> = (0..=255).map(|n| format!("{n:03}")).collect();
        let innermost_list: String = format!(
            "[{}]",
            (0..=127)
                .map(|n| format!("{n}"))
                .collect::<Vec<_>>()
                .join(",")
        );
        let inner_keys: Vec<String> = (240..=495).map(|n| format!("{n}")).collect();
        let inner_object = format!(
            "{{{}:{}}}",
            inner_keys
                .iter()
                .map(|k| format!("\"{k}\""))
                .collect::<Vec<String>>()
                .join(format!(":{innermost_list},").as_str()),
            innermost_list
        );
        let json = format!(
            "{{{}:{}}}",
            keys.iter()
                .map(|k| format!("\"{k}\""))
                .collect::<Vec<String>>()
                .join(format!(":{inner_object},").as_str()),
            inner_object
        );
        // Manually verify raw JSON value size
        let mut variant_builder = VariantBuilder::new();
        variant_builder.append_json(&json)?;
        let (metadata, value) = variant_builder.finish();
        let v = Variant::try_new(&metadata, &value)?;
        let output_string = v.to_json_string()?;
        assert_eq!(output_string, json);
        // Verify metadata size = 1 + 2 + 2 * 497 + 3 * 496
        assert_eq!(metadata.len(), 2485);
        // Verify value size.
        // Size of innermost_list: 1 + 1 + 2*(128 + 1) + 2*128 = 516
        // Size of inner object: 1 + 4 + 2*256 + 3*(256 + 1) + 256 * 516 = 133384
        // Size of json: 1 + 4 + 2*256 + 4*(256 + 1) + 256 * 133384 = 34147849
        assert_eq!(value.len(), 34147849);

        let mut variant_builder = VariantBuilder::new();
        let mut object_builder = variant_builder.new_object();
        keys.iter().for_each(|key| {
            let mut inner_object_builder = object_builder.new_object(key);
            inner_keys.iter().for_each(|inner_key| {
                let mut list_builder = inner_object_builder.new_list(inner_key);
                for i in 0..=127 {
                    list_builder.append_value(Variant::Int8(i));
                }
                list_builder.finish();
            });
            inner_object_builder.finish();
        });
        object_builder.finish();
        let (metadata, value) = variant_builder.finish();
        let variant = Variant::try_new(&metadata, &value)?;

        JsonToVariantTest {
            json: &json,
            expected: variant,
        }
        .run()
    }

    #[test]
    fn test_json_to_variant_unicode() -> Result<(), ArrowError> {
        let json = "{\"爱\":\"अ\",\"a\":1}";
        let mut variant_builder = VariantBuilder::new();
        variant_builder.append_json(json)?;
        let (metadata, value) = variant_builder.finish();
        let v = Variant::try_new(&metadata, &value)?;
        let output_string = v.to_json_string()?;
        assert_eq!(output_string, "{\"a\":1,\"爱\":\"अ\"}");
        let mut variant_builder = VariantBuilder::new();
        let mut object_builder = variant_builder.new_object();
        object_builder.insert("a", Variant::Int8(1));
        object_builder.insert("爱", Variant::ShortString(ShortString::try_new("अ")?));
        object_builder.finish();
        let (metadata, value) = variant_builder.finish();
        let variant = Variant::try_new(&metadata, &value)?;

        assert_eq!(
            value,
            &[
                2u8, 2u8, 0u8, 1u8, 0u8, 2u8, 6u8, 12u8, 1u8, 13u8, 0xe0u8, 0xa4u8, 0x85u8
            ]
        );
        assert_eq!(
            metadata,
            &[17u8, 2u8, 0u8, 1u8, 4u8, 97u8, 0xe7u8, 0x88u8, 0xb1u8]
        );
        JsonToVariantTest {
            json,
            expected: variant,
        }
        .run()
    }
}