Initial project import

tools/v/vlib/encoding/csv/reader.v

@@ -0,0 +1,216 @@
+// Copyright (c) 2019-2024 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module csv
+
+// Once interfaces are further along the idea would be to have something similar to
+// go's io.reader & bufio.reader rather than reading the whole file into string, this
+// would then satisfy that interface. I designed it this way to be easily adapted.
+struct CommentIsDelimiterError {
+	Error
+}
+
+fn (err CommentIsDelimiterError) msg() string {
+	return 'encoding.csv: comment cannot be the same as delimiter'
+}
+
+struct InvalidDelimiterError {
+	Error
+}
+
+fn (err InvalidDelimiterError) msg() string {
+	return 'encoding.csv: invalid delimiter'
+}
+
+struct EndOfFileError {
+	Error
+}
+
+fn (err EndOfFileError) msg() string {
+	return 'encoding.csv: end of file'
+}
+
+struct InvalidLineEndingError {
+	Error
+}
+
+fn (err InvalidLineEndingError) msg() string {
+	return 'encoding.csv: could not find any valid line endings'
+}
+
+struct Reader {
+	// not used yet
+	// has_header        bool
+	// headings          []string
+	data      string
+	delimiter u8
+	comment   u8
+mut:
+	is_mac_pre_osx_le bool
+	row_pos           int
+}
+
+@[params]
+pub struct ReaderConfig {
+pub:
+	delimiter u8 = `,`
+	comment   u8 = `#`
+}
+
+// new_reader initializes a Reader with string data to parse and,
+// optionally, a custom delimiter.
+pub fn new_reader(data string, config ReaderConfig) &Reader {
+	return &Reader{
+		data:      data
+		delimiter: config.delimiter
+		comment:   config.comment
+	}
+}
+
+// read reads a row from the CSV data.
+// If successful, the result holds an array of each column's data.
+pub fn (mut r Reader) read() ![]string {
+	l := r.read_record()!
+	return l
+}
+
+// Once we have multi dimensional array
+// pub fn (mut r Reader) read_all() ?[][]string {
+// 	mut records := []string{}
+// 	for {
+// 		record := r.read_record() or {
+// 			if err.error == err_eof.error {
+// 				return records
+// 			} else {
+// 				return err
+// 			}
+// 		}
+// 		records << record
+// 	}
+// 	return records
+// }
+fn (mut r Reader) read_line() !string {
+	// last record
+	if r.row_pos >= r.data.len {
+		return &EndOfFileError{}
+	}
+	le := if r.is_mac_pre_osx_le { '\r' } else { '\n' }
+	mut i := r.data.index_after(le, r.row_pos) or { -1 }
+	if i == -1 {
+		if r.row_pos == 0 {
+			// check for pre osx mac line endings
+			i = r.data.index_after('\r', r.row_pos) or { -1 }
+			if i != -1 {
+				r.is_mac_pre_osx_le = true
+			} else {
+				// no valid line endings found
+				return &InvalidLineEndingError{}
+			}
+		} else {
+			// No line ending on file
+			i = r.data.len
+		}
+	}
+	mut line := r.data[r.row_pos..i]
+	r.row_pos = i + 1
+	// normalize win line endings (remove extra \r)
+	if !r.is_mac_pre_osx_le && (line.len >= 1 && line[line.len - 1] == `\r`) {
+		line = line[..line.len - 1]
+	}
+	return line
+}
+
+fn (mut r Reader) read_record() ![]string {
+	if r.delimiter == r.comment {
+		return &CommentIsDelimiterError{}
+	}
+	if !valid_delim(r.delimiter) {
+		return &InvalidDelimiterError{}
+	}
+	mut need_read := true
+	mut keep_raw := false
+	mut line := ''
+	mut fields := []string{}
+	mut i := -1
+	for {
+		if need_read {
+			l := r.read_line()!
+			if l.len <= 0 {
+				if keep_raw {
+					line += '\n'
+				}
+				continue
+			} else if l[0] == r.comment {
+				if keep_raw {
+					line += '\n' + l
+				}
+				continue
+			} else {
+				if keep_raw {
+					line += '\n'
+				}
+				line += l
+			}
+			need_read = false
+			keep_raw = false
+		}
+		if line.len == 0 || line[0] != `"` { // not quoted
+			j := line.index(r.delimiter.ascii_str()) or {
+				// last
+				fields << line[..line.len]
+				break
+			}
+			i = j
+			fields << line[..i]
+			line = line[i + 1..]
+			continue
+		} else { // quoted
+			mut need_more := true
+			mut has_double_quotes := false
+			mut j := 0
+			mut n := 1
+			for n < line.len {
+				if line[n] == `"` {
+					if n == line.len - 1 || line[n + 1] != `"` {
+						need_more = false
+						j = n - 1
+						break
+					} else {
+						has_double_quotes = true
+						n++
+					}
+				}
+				n++
+			}
+			if need_more {
+				need_read = true
+				keep_raw = true
+				continue
+			}
+			line = line[1..]
+			if j + 1 == line.len {
+				// last record
+				fields << if has_double_quotes { line[..j].replace('""', '"') } else { line[..j] }
+				break
+			}
+			next := line[j + 1]
+			if next == r.delimiter {
+				fields << if has_double_quotes { line[..j].replace('""', '"') } else { line[..j] }
+				if j + 2 == line.len {
+					line = ''
+				} else {
+					line = line[j + 2..]
+				}
+				continue
+			}
+		}
+		if i <= -1 && fields.len == 0 {
+			return &InvalidDelimiterError{}
+		}
+	}
+	return fields
+}
+
+fn valid_delim(b u8) bool {
+	return b != 0 && b != `"` && b != `\r` && b != `\n`
+}