/*
Copyright © 2026 Craig Williams <craig@avsdev.uk>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package findATender

import (
	"bufio"
	"bytes"
	"io"
	"regexp"
)

// Global regex to identify and catch date-only fields
var invalidDateRegex = regexp.MustCompile(`:\s*"(\d{4}-\d{2}-\d{2})"\s*([,}\s])`)
var invalidPublishedDateRegex = regexp.MustCompile(`"publishedDate":\s*""`)

// The UK Government FindATender service doesn't strictly follow OCDS date
// format. Sometimes it provides dates only, sometimes it sends empty strings
// instead of nulls.
type FindATenderStreamCleaner struct {
	reader *bufio.Reader
	buffer bytes.Buffer
}

func NewOCDSStreamCleaner(r io.Reader) *FindATenderStreamCleaner {
	return &FindATenderStreamCleaner{reader: bufio.NewReader(r)}
}

func (sc *FindATenderStreamCleaner) Read(p []byte) (int, error) {
	if sc.buffer.Len() == 0 {
		line, err := sc.reader.ReadBytes('\n')
		if len(line) > 0 {
			// Convert "2026-11-16" -> "2026-11-16T00:00:00Z"
			line = invalidDateRegex.ReplaceAll(line, []byte(`:"$1T00:00:00Z"`))
			// Convert {publishedDate:""} -> "{publishedDate:null}"
			line = invalidPublishedDateRegex.ReplaceAll(line, []byte(`"publishedDate":null`))
			sc.buffer.Write(line)
		}
		if err != nil {
			if sc.buffer.Len() == 0 {
				return 0, err
			}
		}
	}
	return sc.buffer.Read(p)
}