Add simple CSV file loading interfaces

src/csv/mod.rs

@@ -0,0 +1,245 @@
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::{self, BufRead, BufReader};
+use std::path::Path;
+
+/// Represents the target type for a CSV column.
+#[derive(Debug, Clone)]
+pub enum DataType {
+    Int,
+    Float,
+    Bool,
+    String,
+}
+
+/// Represents a value parsed from the CSV.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Value {
+    Int(i64),
+    Float(f64),
+    Bool(bool),
+    String(String),
+}
+
+/// Convenience alias for a parsed CSV record.
+pub type Record = HashMap<String, Value>;
+
+/// A simple CSV reader that reads records line by line.
+pub struct CsvReader<R: BufRead> {
+    reader: R,
+    separators: Vec<char>,
+    headers: Vec<String>,
+    types: Option<HashMap<String, DataType>>,
+}
+
+impl<R: BufRead> CsvReader<R> {
+    /// Create a new CSV reader from a [`BufRead`] source.
+    /// The first line is expected to contain headers.
+    /// `separators` is a list of characters considered as field separators.
+    /// `types` optionally maps column names to target data types.
+    pub fn new(mut reader: R, separators: Vec<char>, types: Option<HashMap<String, DataType>>) -> io::Result<Self> {
+        let mut first_line = String::new();
+        reader.read_line(&mut first_line)?;
+        let headers = parse_line(&first_line, &separators);
+        Ok(Self { reader, separators, headers, types })
+    }
+
+    /// Return the headers of the CSV file.
+    pub fn headers(&self) -> &[String] {
+        &self.headers
+    }
+
+    /// Read the next record. Returns `Ok(None)` on EOF.
+    pub fn read_record(&mut self) -> io::Result<Option<Record>> {
+        let mut line = String::new();
+        if self.reader.read_line(&mut line)? == 0 {
+            return Ok(None);
+        }
+        let fields = parse_line(&line, &self.separators);
+        let mut record = HashMap::new();
+
+        for (i, header) in self.headers.iter().enumerate() {
+            let field = fields.get(i).cloned().unwrap_or_default();
+            let value = match &self.types {
+                Some(map) => {
+                    if let Some(dt) = map.get(header) {
+                        parse_with_type(&field, dt)
+                    } else {
+                        Value::String(field)
+                    }
+                }
+                None => parse_auto(&field),
+            };
+            record.insert(header.clone(), value);
+        }
+
+        Ok(Some(record))
+    }
+}
+
+impl<R: BufRead> Iterator for CsvReader<R> {
+    type Item = io::Result<Record>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.read_record() {
+            Ok(Some(rec)) => Some(Ok(rec)),
+            Ok(None) => None,
+            Err(e) => Some(Err(e)),
+        }
+    }
+}
+
+impl<R: BufRead> CsvReader<R> {
+    /// Read all remaining records into a vector.
+    pub fn read_all(&mut self) -> io::Result<Vec<Record>> {
+        let mut records = Vec::new();
+        while let Some(rec) = self.read_record()? {
+            records.push(rec);
+        }
+        Ok(records)
+    }
+}
+
+/// Create an iterator over records from a file path using default settings.
+pub fn reader<P: AsRef<Path>>(path: P) -> io::Result<CsvReader<BufReader<File>>> {
+    reader_with(path, vec![',' ], None)
+}
+
+/// Create an iterator over records from a file path with custom separators and type mapping.
+pub fn reader_with<P: AsRef<Path>>(path: P, separators: Vec<char>, types: Option<HashMap<String, DataType>>) -> io::Result<CsvReader<BufReader<File>>> {
+    let file = File::open(path)?;
+    let reader = BufReader::new(file);
+    CsvReader::new(reader, separators, types)
+}
+
+/// Read an entire CSV file into memory using default settings.
+pub fn read_file<P: AsRef<Path>>(path: P) -> io::Result<Vec<Record>> {
+    read_file_with(path, vec![',' ], None)
+}
+
+/// Read an entire CSV file into memory with custom separators and type mapping.
+pub fn read_file_with<P: AsRef<Path>>(path: P, separators: Vec<char>, types: Option<HashMap<String, DataType>>) -> io::Result<Vec<Record>> {
+    let mut reader = reader_with(path, separators, types)?;
+    reader.read_all()
+}
+
+fn parse_with_type(s: &str, ty: &DataType) -> Value {
+    match ty {
+        DataType::Int => s.parse::<i64>().map(Value::Int).unwrap_or_else(|_| Value::String(s.to_string())),
+        DataType::Float => s.parse::<f64>().map(Value::Float).unwrap_or_else(|_| Value::String(s.to_string())),
+        DataType::Bool => s.parse::<bool>().map(Value::Bool).unwrap_or_else(|_| Value::String(s.to_string())),
+        DataType::String => Value::String(s.to_string()),
+    }
+}
+
+fn parse_auto(s: &str) -> Value {
+    if let Ok(i) = s.parse::<i64>() {
+        Value::Int(i)
+    } else if let Ok(f) = s.parse::<f64>() {
+        Value::Float(f)
+    } else if let Ok(b) = s.parse::<bool>() {
+        Value::Bool(b)
+    } else {
+        Value::String(s.to_string())
+    }
+}
+
+fn parse_line(line: &str, separators: &[char]) -> Vec<String> {
+    let mut fields = Vec::new();
+    let mut current = String::new();
+    let mut in_quotes: Option<char> = None;
+    let chars: Vec<char> = line.chars().collect();
+    let mut i = 0;
+
+    while i < chars.len() {
+        let c = chars[i];
+        if let Some(q) = in_quotes {
+            if c == q {
+                if i + 1 < chars.len() && chars[i + 1] == q {
+                    current.push(q);
+                    i += 1; // skip escaped quote
+                } else {
+                    in_quotes = None;
+                }
+            } else {
+                current.push(c);
+            }
+        } else if c == '"' || c == '\'' {
+            in_quotes = Some(c);
+        } else if separators.contains(&c) {
+            fields.push(current.clone());
+            current.clear();
+        } else if c == '\r' {
+            // Ignore carriage returns
+        } else if c == '\n' {
+            break;
+        } else {
+            current.push(c);
+        }
+        i += 1;
+    }
+
+    fields.push(current);
+    fields
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Cursor;
+
+    #[test]
+    fn test_parse_line() {
+        let line = "a,'b,c',\"d\"\"e\",f";
+        let fields = parse_line(line, &[',']);
+        assert_eq!(fields, vec!["a", "b,c", "d\"e", "f"]);
+    }
+
+    #[test]
+    fn test_reader_auto() {
+        let data = "a,b,c\n1,2.5,true\n4,5.0,false\n";
+        let cursor = Cursor::new(data);
+        let mut reader = CsvReader::new(cursor, vec![','], None).unwrap();
+        let rec = reader.next().unwrap().unwrap();
+        assert_eq!(rec.get("a"), Some(&Value::Int(1)));
+        assert_eq!(rec.get("b"), Some(&Value::Float(2.5)));
+        assert_eq!(rec.get("c"), Some(&Value::Bool(true)));
+    }
+
+    #[test]
+    fn test_reader_with_types() {
+        let data = "a;b;c\n1;2;3\n";
+        let cursor = Cursor::new(data);
+        let mut types = HashMap::new();
+        types.insert("a".to_string(), DataType::Int);
+        types.insert("b".to_string(), DataType::Int);
+        types.insert("c".to_string(), DataType::String);
+        let mut reader = CsvReader::new(cursor, vec![';', ','], Some(types)).unwrap();
+        let rec = reader.next().unwrap().unwrap();
+        assert_eq!(rec.get("a"), Some(&Value::Int(1)));
+        assert_eq!(rec.get("b"), Some(&Value::Int(2)));
+        assert_eq!(rec.get("c"), Some(&Value::String("3".to_string())));
+    }
+
+    #[test]
+    fn test_read_file_all() {
+        let path = std::env::temp_dir().join("csv_full_test.csv");
+        std::fs::write(&path, "a,b\n1,2\n3,4\n").unwrap();
+        let records = read_file(&path).unwrap();
+        assert_eq!(records.len(), 2);
+        assert_eq!(records[1].get("b"), Some(&Value::Int(4)));
+        std::fs::remove_file(path).unwrap();
+    }
+
+    #[test]
+    fn test_reader_from_path() {
+        let path = std::env::temp_dir().join("csv_iter_test.csv");
+        std::fs::write(&path, "a,b\n5,6\n").unwrap();
+        let mut iter = reader(&path).unwrap();
+        let rec = iter.next().unwrap().unwrap();
+        assert_eq!(rec.get("a"), Some(&Value::Int(5)));
+        assert_eq!(rec.get("b"), Some(&Value::Int(6)));
+        std::fs::remove_file(path).unwrap();
+    }
+}
+

src/lib.rs

@@ -14,3 +14,6 @@ pub mod compute;
 
 /// Documentation for the [`crate::random`] module.
 pub mod random;
+
+/// Documentation for the [`crate::csv`] module.
+pub mod csv;