vantage_csv/
csv.rs

1use std::path::PathBuf;
2
3use indexmap::IndexMap;
4use vantage_core::error;
5use vantage_dataset::traits::Result;
6use vantage_table::column::core::Column;
7use vantage_table::traits::column_like::ColumnLike;
8use vantage_types::Record;
9
10use crate::type_system::{AnyCsvType, parse_with_type, variant_from_type_name};
11
12/// CSV backend for Vantage — reads data from CSV files.
13///
14/// Each table maps to a CSV file: `{base_dir}/{table_name}.csv`.
15/// CSV is a read-only data source — write operations return errors.
16#[derive(Clone, Debug)]
17pub struct Csv {
18    base_dir: PathBuf,
19    pub(crate) id_column: String,
20}
21
22impl Csv {
23    /// Create a new CSV data source reading files from `base_dir`.
24    pub fn new(base_dir: impl Into<PathBuf>) -> Self {
25        Self {
26            base_dir: base_dir.into(),
27            id_column: "id".to_string(),
28        }
29    }
30
31    /// Set which CSV column to use as the record ID.
32    pub fn with_id_column(mut self, column: impl Into<String>) -> Self {
33        self.id_column = column.into();
34        self
35    }
36
37    /// Get the file path for a given table name.
38    fn file_path(&self, table_name: &str) -> PathBuf {
39        self.base_dir.join(format!("{}.csv", table_name))
40    }
41
42    /// Parse a CSV file and return all rows as records.
43    ///
44    /// Column types from the table definition are used to parse values.
45    /// Fields without a known column type are stored as plain strings.
46    pub(crate) fn read_csv(
47        &self,
48        table_name: &str,
49        columns: &IndexMap<String, Column<AnyCsvType>>,
50    ) -> Result<IndexMap<String, Record<AnyCsvType>>> {
51        let path = self.file_path(table_name);
52        let mut reader = csv::Reader::from_path(&path)
53            .map_err(|e| error!("Failed to open CSV file", path = path.display(), detail = e))?;
54
55        let headers = reader
56            .headers()
57            .map_err(|e| error!("Failed to read CSV headers", detail = e))?
58            .clone();
59
60        let id_col_index = headers.iter().position(|h| h == self.id_column);
61
62        let mut records = IndexMap::new();
63
64        for (row_idx, result) in reader.records().enumerate() {
65            let csv_record = result.map_err(|e| error!("Failed to read CSV row", detail = e))?;
66
67            let id = if let Some(idx) = id_col_index {
68                csv_record.get(idx).unwrap_or_default().to_string()
69            } else {
70                row_idx.to_string()
71            };
72
73            let mut record = Record::new();
74            for (i, field) in csv_record.iter().enumerate() {
75                if let Some(header) = headers.get(i) {
76                    let variant = columns
77                        .get(header)
78                        .and_then(|col| variant_from_type_name(col.get_type()));
79                    record.insert(header.to_string(), parse_with_type(field, variant));
80                }
81            }
82
83            records.insert(id, record);
84        }
85
86        Ok(records)
87    }
88}
vantage_csv/csv.rs

vantage_csv/
csv.rs
