cherry_cast/
lib.rs

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use std::sync::Arc;

use anyhow::{Context, Result};
use arrow::{
    array::{builder, Array, BinaryArray, Decimal256Array, RecordBatch, StringArray},
    compute::CastOptions,
    datatypes::{DataType, Field, Schema},
};
use ruint::aliases::U256;

/// Casts columns according to given (column name, target data type) pairs.
///
/// Returns error if casting a row fails and `allow_cast_fail` is set to `false`.
/// Writes `null` to output if casting a row fails and `allow_cast_fail` is set to `true`.
pub fn cast<S: AsRef<str>>(
    map: &[(S, DataType)],
    data: &RecordBatch,
    allow_cast_fail: bool,
) -> Result<RecordBatch> {
    let schema = cast_schema(map, data.schema_ref()).context("cast schema")?;

    let mut arrays = Vec::with_capacity(data.num_columns());

    let cast_opt = CastOptions {
        safe: !allow_cast_fail,
        ..Default::default()
    };

    for (col, field) in data.columns().iter().zip(data.schema_ref().fields().iter()) {
        let cast_target = map.iter().find(|x| x.0.as_ref() == field.name());

        let col = match cast_target {
            Some(tgt) => Arc::new(
                arrow::compute::cast_with_options(col, &tgt.1, &cast_opt)
                    .with_context(|| format!("Failed when casting column '{}'", field.name()))?,
            ),
            None => col.clone(),
        };

        arrays.push(col);
    }

    let batch = RecordBatch::try_new(Arc::new(schema), arrays).context("construct record batch")?;

    Ok(batch)
}

/// Casts column types according to given (column name, target data type) pairs.
pub fn cast_schema<S: AsRef<str>>(map: &[(S, DataType)], schema: &Schema) -> Result<Schema> {
    let mut fields = schema.fields().to_vec();

    for f in fields.iter_mut() {
        let cast_target = map.iter().find(|x| x.0.as_ref() == f.name());

        if let Some(tgt) = cast_target {
            *f = Arc::new(Field::new(f.name(), tgt.1.clone(), f.is_nullable()));
        }
    }

    Ok(Schema::new(fields))
}

pub fn hex_encode<const PREFIXED: bool>(data: &RecordBatch) -> Result<RecordBatch> {
    let schema = schema_binary_to_string(data.schema_ref());
    let mut columns = Vec::<Arc<dyn Array>>::with_capacity(data.columns().len());

    for col in data.columns().iter() {
        if col.data_type() == &DataType::Binary {
            columns.push(Arc::new(hex_encode_column::<PREFIXED>(
                col.as_any().downcast_ref::<BinaryArray>().unwrap(),
            )));
        } else {
            columns.push(col.clone());
        }
    }

    RecordBatch::try_new(Arc::new(schema), columns).context("construct arrow batch")
}

pub fn hex_encode_column<const PREFIXED: bool>(col: &BinaryArray) -> StringArray {
    let mut arr =
        builder::StringBuilder::with_capacity(col.len(), (col.value_data().len() + 2) * 2);

    for v in col.iter() {
        match v {
            Some(v) => {
                // TODO: avoid allocation here and use a scratch buffer to encode hex into or write to arrow buffer
                // directly somehow.
                let v = if PREFIXED {
                    format!("0x{}", faster_hex::hex_string(v))
                } else {
                    faster_hex::hex_string(v)
                };

                arr.append_value(v);
            }
            None => arr.append_null(),
        }
    }

    arr.finish()
}

/// Converts binary fields to string in the schema
///
/// Intended to be used with encode hex functions
pub fn schema_binary_to_string(schema: &Schema) -> Schema {
    let mut fields = Vec::<Arc<Field>>::with_capacity(schema.fields().len());

    for f in schema.fields().iter() {
        if f.data_type() == &DataType::Binary {
            fields.push(Arc::new(Field::new(
                f.name().clone(),
                DataType::Utf8,
                f.is_nullable(),
            )));
        } else {
            fields.push(f.clone());
        }
    }

    Schema::new(fields)
}

/// Converts decimal256 fields to binary in the schema
///
/// Intended to be used with u256_to_binary function
pub fn schema_decimal256_to_binary(schema: &Schema) -> Schema {
    let mut fields = Vec::<Arc<Field>>::with_capacity(schema.fields().len());

    for f in schema.fields().iter() {
        if f.data_type() == &DataType::Decimal256(76, 0) {
            fields.push(Arc::new(Field::new(
                f.name().clone(),
                DataType::Binary,
                f.is_nullable(),
            )));
        } else {
            fields.push(f.clone());
        }
    }

    Schema::new(fields)
}

pub fn hex_decode_column<const PREFIXED: bool>(col: &StringArray) -> Result<BinaryArray> {
    let mut arr = builder::BinaryBuilder::with_capacity(col.len(), col.value_data().len() / 2);

    for v in col.iter() {
        match v {
            // TODO: this should be optimized by removing allocations if needed
            Some(v) => {
                let v = v.as_bytes();
                let v = if PREFIXED {
                    v.get(2..).context("index into prefix hex encoded value")?
                } else {
                    v
                };

                let len = v.len();
                let mut dst = vec![0; (len + 1) / 2];

                faster_hex::hex_decode(v, &mut dst).context("hex decode")?;

                arr.append_value(dst);
            }
            None => arr.append_null(),
        }
    }

    Ok(arr.finish())
}

pub fn u256_column_from_binary(col: &BinaryArray) -> Result<Decimal256Array> {
    let mut arr = builder::Decimal256Builder::with_capacity(col.len());

    for v in col.iter() {
        match v {
            Some(v) => {
                let num = U256::try_from_be_slice(v).context("parse u256")?;
                let num = arrow::datatypes::i256::from_be_bytes(num.to_be_bytes::<32>());
                arr.append_value(num);
            }
            None => arr.append_null(),
        }
    }

    Ok(arr.finish())
}

pub fn u256_column_to_binary(col: &Decimal256Array) -> BinaryArray {
    let mut arr = builder::BinaryBuilder::with_capacity(col.len(), col.len() * 32);

    for v in col.iter() {
        match v {
            Some(v) => {
                let num = U256::from_be_bytes::<32>(v.to_be_bytes());
                arr.append_value(num.to_be_bytes_trimmed_vec());
            }
            None => {
                arr.append_null();
            }
        }
    }

    arr.finish()
}

/// Converts all Decimal256 (U256) columns in the batch to big endian binary values
pub fn u256_to_binary(data: &RecordBatch) -> Result<RecordBatch> {
    let schema = schema_binary_to_string(data.schema_ref());
    let mut columns = Vec::<Arc<dyn Array>>::with_capacity(data.columns().len());

    for col in data.columns().iter() {
        if col.data_type() == &DataType::Decimal256(76, 0) {
            let mut arr = builder::BinaryBuilder::new();

            let col = col.as_any().downcast_ref::<Decimal256Array>().unwrap();

            for val in col.iter() {
                arr.append_option(val.map(|v| v.to_be_bytes()));
            }

            columns.push(Arc::new(arr.finish()));
        } else {
            columns.push(col.clone());
        }
    }

    RecordBatch::try_new(Arc::new(schema), columns).context("construct arrow batch")
}