use crate::model::DecodedBarcode;

pub fn extract_barcodes(bytes: &[u8]) -> Vec<DecodedBarcode> {
    extract_from_zpl_bytes(bytes)
}

pub fn extract_from_zpl(input: &str) -> Vec<DecodedBarcode> {
    extract_from_zpl_bytes(input.as_bytes())
}

fn extract_from_zpl_bytes(bytes: &[u8]) -> Vec<DecodedBarcode> {
    let mut index = 0usize;
    let mut pending_format: Option<String> = None;
    let mut barcodes = Vec::new();

    while index + 2 < bytes.len() {
        if bytes[index] != b'^' && bytes[index] != b'~' {
            index += 1;
            continue;
        }

        let command_start = index;
        let command = &bytes[index + 1..index + 3];
        index += 3;

        if let Some(format) = barcode_format(command) {
            pending_format = Some(format.to_string());
            continue;
        }

        if command == b"FD" {
            let end = find_bytes(&bytes[index..], b"^FS")
                .map(|offset| index + offset)
                .unwrap_or(bytes.len());
            if let Some(format) = pending_format.take() {
                let raw = String::from_utf8_lossy(&bytes[index..end]);
                let value = normalize_field_data(raw.trim());
                if !value.is_empty() {
                    barcodes.push(DecodedBarcode { format, value });
                }
            }
            index = end.saturating_add(3);
            continue;
        }

        if command == b"FS" || command == b"XZ" {
            pending_format = None;
        }

        if index <= command_start {
            index = command_start + 1;
        }
    }

    barcodes
}

fn barcode_format(command: &[u8]) -> Option<&'static str> {
    match command {
        b"BC" => Some("CODE_128"),
        b"B3" => Some("CODE_39"),
        b"BE" => Some("EAN_13"),
        b"B8" => Some("EAN_8"),
        b"BU" => Some("UPC_A"),
        b"B9" => Some("UPC_E"),
        b"B2" => Some("ITF"),
        b"BQ" => Some("QR_CODE"),
        b"BX" => Some("DATA_MATRIX"),
        b"B7" => Some("PDF_417"),
        b"BA" => Some("CODE_93"),
        _ => None,
    }
}

fn find_bytes(haystack: &[u8], needle: &[u8]) -> Option<usize> {
    if needle.is_empty() {
        return Some(0);
    }
    haystack.windows(needle.len()).position(|window| window == needle)
}

fn normalize_field_data(raw: &str) -> String {
    let mut value = raw.to_string();

    // Zebra Code 128 control sequences commonly select code sets or emit FNC1.
    for prefix in [">;", ">:", ">9"] {
        if value.starts_with(prefix) {
            value = value[prefix.len()..].to_string();
            break;
        }
    }
    value = value.replace(">8", "\u{001d}");

    // ^FH defaults to '_' as the hex escape character. Decode common escaped bytes.
    let hex = regex::Regex::new(r"_([0-9A-Fa-f]{2})").expect("valid regex");
    hex.replace_all(&value, |caps: &regex::Captures<'_>| {
        u8::from_str_radix(&caps[1], 16)
            .ok()
            .map(char::from)
            .unwrap_or('_')
            .to_string()
    })
    .into_owned()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn extracts_multiple_zpl_barcode_types() {
        let zpl = "^XA^FO10,10^BCN,80,Y,N,N^FD>;0123456789012^FS^FO10,100^BQN,2,5^FDLA,HELLO^FS^XZ";
        let found = extract_from_zpl(zpl);
        assert_eq!(
            found,
            vec![
                DecodedBarcode { format: "CODE_128".into(), value: "0123456789012".into() },
                DecodedBarcode { format: "QR_CODE".into(), value: "LA,HELLO".into() },
            ]
        );
    }

    #[test]
    fn preserves_gs1_separator_for_fnc1() {
        let zpl = "^XA^BCN,80,N,N,N^FD>801095011015300310ABC^FS^XZ";
        let found = extract_from_zpl(zpl);
        assert_eq!(found[0].value, "\u{001d}01095011015300310ABC");
    }

    #[test]
    fn ignores_normal_text_fields() {
        let zpl = "^XA^FO10,10^A0N,30,30^FDNOT-A-BARCODE^FS^XZ";
        assert!(extract_from_zpl(zpl).is_empty());
    }

    #[test]
    fn arbitrary_binary_printer_data_never_panics() {
        let payload = [
            0x1b, b'@', 0xff, 0x00, 0xfe, b'^', 0xff, 0xfd, 0x1b, b'(', b'G',
            0x10, 0x00, 0x80, 0x81, 0x82, b'^', b'F', b'D', 0xf0, 0x9f, 0x92,
            0xa9, b'^', b'F', b'S',
        ];
        let found = extract_barcodes(&payload);
        assert!(found.is_empty());
    }
}