#![deny(warnings)]
//! [TSM.ID].[11031972] -- Platform X Ecosystem
//! xcu-parquet -- Columnar Storage Engine (Parquet-like)
pub mod blackbox;
use std::collections::HashMap;

#[derive(Debug)]
pub enum ParquetError { ColumnNotFound(String), TypeMismatch(String), WriteError(String) }
impl std::fmt::Display for ParquetError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self { Self::ColumnNotFound(e) => write!(f, "Column: {e}"), Self::TypeMismatch(e) => write!(f, "Type: {e}"), Self::WriteError(e) => write!(f, "Write: {e}") }
    }
}
impl std::error::Error for ParquetError {}

#[derive(Debug, Clone)]
pub enum ColumnValue { Int64(i64), Float64(f64), Str(String), Bool(bool), Null }

#[derive(Debug, Clone)]
pub struct ColumnSchema { pub name: String, pub col_type: String, pub nullable: bool }

pub struct ColumnStore {
    schema: Vec<ColumnSchema>,
    columns: HashMap<String, Vec<ColumnValue>>,
    row_count: usize,
}

impl ColumnStore {
    pub fn new(schema: Vec<ColumnSchema>) -> Self {
        let mut columns = HashMap::new();
        for col in &schema { columns.insert(col.name.clone(), Vec::new()); }
        Self { schema, columns, row_count: 0 }
    }

    /// Insert a row (HashMap of column_name → value)
    pub fn insert_row(&mut self, row: HashMap<String, ColumnValue>) -> Result<(), ParquetError> {
        for col in &self.schema {
            let val = row.get(&col.name).cloned().unwrap_or(ColumnValue::Null);
            if let ColumnValue::Null = val {
                if !col.nullable { return Err(ParquetError::TypeMismatch(format!("{} is not nullable", col.name))); }
            }
            self.columns.get_mut(&col.name)
                .ok_or_else(|| ParquetError::ColumnNotFound(col.name.clone()))?
                .push(val);
        }
        self.row_count += 1;
        Ok(())
    }

    /// Read a column (full scan)
    pub fn read_column(&self, name: &str) -> Result<&[ColumnValue], ParquetError> {
        self.columns.get(name).map(|v| v.as_slice())
            .ok_or_else(|| ParquetError::ColumnNotFound(name.into()))
    }

    /// Filter rows where column matches predicate
    pub fn filter<F>(&self, column: &str, predicate: F) -> Result<Vec<usize>, ParquetError>
    where F: Fn(&ColumnValue) -> bool {
        let col = self.columns.get(column).ok_or_else(|| ParquetError::ColumnNotFound(column.into()))?;
        Ok(col.iter().enumerate().filter(|(_, v)| predicate(v)).map(|(i, _)| i).collect())
    }

    /// Aggregate: sum of numeric column
    pub fn sum(&self, column: &str) -> Result<f64, ParquetError> {
        let col = self.columns.get(column).ok_or_else(|| ParquetError::ColumnNotFound(column.into()))?;
        let mut total = 0.0;
        for v in col {
            match v { ColumnValue::Int64(n) => total += *n as f64, ColumnValue::Float64(n) => total += n, _ => {} }
        }
        Ok(total)
    }

    /// Aggregate: count non-null
    pub fn count(&self, column: &str) -> Result<usize, ParquetError> {
        let col = self.columns.get(column).ok_or_else(|| ParquetError::ColumnNotFound(column.into()))?;
        Ok(col.iter().filter(|v| !matches!(v, ColumnValue::Null)).count())
    }

    /// Compute min/max for numeric column
    pub fn min_max(&self, column: &str) -> Result<(f64, f64), ParquetError> {
        let col = self.columns.get(column).ok_or_else(|| ParquetError::ColumnNotFound(column.into()))?;
        let mut min = f64::INFINITY;
        let mut max = f64::NEG_INFINITY;
        for v in col {
            let val = match v { ColumnValue::Int64(n) => *n as f64, ColumnValue::Float64(n) => *n, _ => continue };
            if val < min { min = val; }
            if val > max { max = val; }
        }
        Ok((min, max))
    }

    pub fn row_count(&self) -> usize { self.row_count }
    pub fn column_count(&self) -> usize { self.schema.len() }
}

#[cfg(test)]
mod tests {
    use super::*;
    fn make_store() -> ColumnStore {
        let schema = vec![
            ColumnSchema { name: "id".into(), col_type: "int64".into(), nullable: false },
            ColumnSchema { name: "value".into(), col_type: "float64".into(), nullable: true },
            ColumnSchema { name: "name".into(), col_type: "string".into(), nullable: true },
        ];
        let mut store = ColumnStore::new(schema);
        for i in 0..10 {
            let mut row = HashMap::new();
            row.insert("id".into(), ColumnValue::Int64(i));
            row.insert("value".into(), ColumnValue::Float64(i as f64 * 1.5));
            row.insert("name".into(), ColumnValue::Str(format!("item-{i}")));
            store.insert_row(row).unwrap();
        }
        store
    }
    #[test]
    fn test_sum() { let s = make_store(); assert_eq!(s.sum("id").unwrap(), 45.0); }
    #[test]
    fn test_filter() {
        let s = make_store();
        let rows = s.filter("value", |v| matches!(v, ColumnValue::Float64(f) if *f > 10.0)).unwrap();
        assert!(!rows.is_empty());
    }
    #[test]
    fn test_min_max() { let s = make_store(); let (min, max) = s.min_max("id").unwrap(); assert_eq!(min, 0.0); assert_eq!(max, 9.0); }
}