sheeter-engine 0.9.0

use crate::{CanonicalValue, Format, SqlDialect};
use std::error::Error;

/// Prints a structural summary of an input document.
///
/// Reports the format, the number of top-level documents (sheets), and for
/// each sheet the number of rows and columns with inferred types.
///
/// # Examples
///
/// ```
/// use sheeter_engine::{inspect, Format};
///
/// let report = inspect(b"name,age\nAlice,30\nBob,25\n", Format::Csv).unwrap();
/// assert!(report.contains("rows: 2"));
/// assert!(report.contains("name"));
/// ```
pub fn inspect(input: &[u8], format: Format) -> Result<String, Box<dyn Error>> {
    let sheets = load_sheets(input, format)?;
    let mut out = String::new();
    out.push_str(&format!("format: {}\n", format_name(format)));
    out.push_str(&format!("documents: {}\n", sheets.len()));
    for (name, value) in &sheets {
        describe_sheet(&mut out, name, value);
    }
    Ok(out)
}

fn format_name(f: Format) -> &'static str {
    match f {
        Format::Csv => "csv",
        Format::Tsv => "tsv",
        Format::Json => "json",
        Format::Yaml => "yaml",
        Format::Xml => "xml",
        Format::Toml => "toml",
        Format::Xlsx => "xlsx",
        Format::Sql => "sql",
    }
}

fn load_sheets(
    input: &[u8],
    format: Format,
) -> Result<Vec<(String, CanonicalValue)>, Box<dyn Error>> {
    match format {
        Format::Xlsx => CanonicalValue::from_xlsx_workbook(input),
        Format::Sql => {
            let text = std::str::from_utf8(input)?;
            CanonicalValue::from_sql_workbook(text, SqlDialect::Generic)
        }
        _ => {
            let text = std::str::from_utf8(input)?;
            let hub = match format {
                Format::Csv => CanonicalValue::from_csv(text)?,
                Format::Tsv => CanonicalValue::from_tsv(text)?,
                Format::Json => CanonicalValue::from_json(text)?,
                Format::Yaml => CanonicalValue::from_yaml(text)?,
                Format::Xml => CanonicalValue::from_xml(text)?,
                Format::Toml => CanonicalValue::from_toml(text)?,
                Format::Xlsx | Format::Sql => unreachable!(),
            };
            Ok(vec![("Sheet1".to_string(), hub)])
        }
    }
}

fn describe_sheet(out: &mut String, name: &str, value: &CanonicalValue) {
    out.push_str(&format!("  {name}:\n"));
    match value {
        CanonicalValue::Array(rows) => {
            let cols = collect_headers(rows);
            out.push_str(&format!("    rows: {}\n", rows.len()));
            out.push_str(&format!("    columns: {}\n", cols.len()));
            for (i, col) in cols.iter().enumerate() {
                let ty = infer_type(rows, col);
                out.push_str(&format!("      {}: {} ({})\n", i + 1, col, ty));
            }
        }
        CanonicalValue::Object(o) => {
            out.push_str(&format!("    fields: {}\n", o.len()));
            for (k, v) in o {
                out.push_str(&format!("      {k}: {}\n", infer_scalar(v)));
            }
        }
        CanonicalValue::String(s) => {
            out.push_str(&format!("    scalar: string ({} bytes)\n", s.len()));
        }
        CanonicalValue::Number(n) => out.push_str(&format!("    scalar: number ({n})\n")),
        CanonicalValue::Bool(b) => out.push_str(&format!("    scalar: bool ({b})\n")),
        CanonicalValue::Null => out.push_str("    scalar: null\n"),
    }
}

fn collect_headers(rows: &[CanonicalValue]) -> Vec<String> {
    let mut out: Vec<String> = Vec::new();
    for row in rows {
        if let CanonicalValue::Object(o) = row {
            for (k, _) in o {
                if !out.contains(k) {
                    out.push(k.clone());
                }
            }
        }
    }
    out
}

fn infer_type(rows: &[CanonicalValue], col: &str) -> &'static str {
    let mut has_int = false;
    let mut has_float = false;
    let mut has_str = false;
    let mut has_bool = false;
    let mut has_null = false;
    for row in rows {
        if let CanonicalValue::Object(o) = row {
            match o.iter().find(|(k, _)| k == col).map(|(_, v)| v) {
                Some(CanonicalValue::Number(n)) => {
                    if n.is_i64() || n.is_u64() {
                        has_int = true;
                    } else {
                        has_float = true;
                    }
                }
                Some(CanonicalValue::String(_)) => has_str = true,
                Some(CanonicalValue::Bool(_)) => has_bool = true,
                Some(CanonicalValue::Null) | None => has_null = true,
                _ => has_str = true,
            }
        }
    }
    match (has_int, has_float, has_str, has_bool, has_null) {
        (true, false, false, false, _) => "integer",
        (_, true, false, false, _) => "number",
        (false, false, false, true, _) => "boolean",
        (false, false, true, false, _) => "string",
        (false, false, false, false, true) => "null",
        _ => "mixed",
    }
}

fn infer_scalar(v: &CanonicalValue) -> &'static str {
    match v {
        CanonicalValue::Null => "null",
        CanonicalValue::Bool(_) => "boolean",
        CanonicalValue::Number(n) if n.is_i64() || n.is_u64() => "integer",
        CanonicalValue::Number(_) => "number",
        CanonicalValue::String(_) => "string",
        CanonicalValue::Array(_) => "array",
        CanonicalValue::Object(_) => "object",
    }
}