auto_encoder 0.2.4

Auto encoding library
Documentation 
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//! # Auto Encoder
//!
//! `auto_encoder` is a Rust library designed to automatically detect and encode various text and binary file formats, along with specific language encodings.
//!
//! ## Features
//!
//! - **Automatic Encoding Detection**: Detects text encoding based on locale or content.
//! - **Binary Format Detection**: Checks if a given file is a known binary format by inspecting its initial bytes.
//! - **HTML Language Detection**: Extracts and detects the language of an HTML document from its content.
//!
//! ## Usage
//!
//! Here's a quick example to get you started:
//!
//! ### Encoding Detection
//!
//! Automatically detect the encoding for a given locale:
//!
//! ```rust
//! use auto_encoder::encoding_for_locale;
//!
//! let encoding = encoding_for_locale("ja-jp").unwrap();
//! println!("Encoding for Japanese locale: {:?}", encoding);
//! ```
//!
//! Encode bytes from a given HTML content and language:
//!
//! ```rust
//! use auto_encoder::encode_bytes_from_language;
//!
//! let html_content = b"\xE3\x81\x93\xE3\x82\x93\xE3\x81\xAB\xE3\x81\xA1\xE3\x81\xAF\xE3\x80\x81\xE4\xB8\x96\xE7\x95\x8C\xEF\xBC\x81";
//! let encoded = encode_bytes_from_language(html_content, "ja");
//! println!("Encoded content: {}", encoded);
//! ```
//!
//! ### Binary Format Detection
//!
//! Check if a given file content is a known binary format:
//!
//! ```rust
//! use auto_encoder::is_binary_file;
//!
//! let file_content = &[0xFF, 0xD8, 0xFF]; // JPEG file signature
//! let is_binary = is_binary_file(file_content);
//! println!("Is the file a known binary format? {}", is_binary);
//! ```
//!
//! ### HTML Language Detection
//!
//! Detect the language attribute from an HTML document:
//!
//! ```rust
//! use auto_encoder::detect_language;
//!
//! let html_content = br#"<html lang="en"><head><title>Test</title></head><body></body></html>"#;
//! let language = detect_language(html_content).unwrap();
//! println!("Language detected: {}", language);
//! ```
pub mod detect;
pub mod meta;
pub use detect::{detect_encoding, detect_language, find_subsequence, is_binary_file};
use encoding_rs::CoderResult;
use meta::ENCODINGS_BY_LOCALE;
pub extern crate encoding_rs;

/// Get encoding for the locale if found
pub fn encoding_for_locale(locale: &str) -> Option<&'static encoding_rs::Encoding> {
    let mut buf = [0u8; 32];
    let locale_bytes = locale.as_bytes();
    if locale_bytes.len() > buf.len() {
        return None;
    }
    for (i, &b) in locale_bytes.iter().enumerate() {
        buf[i] = b.to_ascii_lowercase();
    }
    let key = std::str::from_utf8(&buf[..locale_bytes.len()]).ok()?;
    ENCODINGS_BY_LOCALE.get(key).copied()
}

fn decode_to_string(html: &[u8], encoding: &'static encoding_rs::Encoding) -> String {
    let mut decoder = encoding.new_decoder();
    let mut total_read = 0usize;
    let mut output = String::with_capacity(html.len());

    let mut process = |buffer: &mut str| {
        let mut bytes_in_buffer = 0usize;

        loop {
            let (result, read, written, _) = decoder.decode_to_str(
                &html[total_read..],
                &mut buffer[bytes_in_buffer..],
                false,
            );
            total_read += read;
            bytes_in_buffer += written;
            match result {
                CoderResult::InputEmpty => break,
                CoderResult::OutputFull => {
                    output.push_str(&buffer[..bytes_in_buffer]);
                    bytes_in_buffer = 0;
                }
            }
        }

        loop {
            let (result, _, written, _) =
                decoder.decode_to_str(b"", &mut buffer[bytes_in_buffer..], true);
            bytes_in_buffer += written;
            output.push_str(&buffer[..bytes_in_buffer]);
            bytes_in_buffer = 0;
            match result {
                CoderResult::InputEmpty => break,
                CoderResult::OutputFull => continue,
            }
        }
    };

    match html.len() {
        15001..=usize::MAX => {
            let mut buf = [0u8; 8192];
            process(std::str::from_utf8_mut(&mut buf[..]).unwrap_or_default())
        }
        1000..=15000 => {
            let mut buf = [0u8; 2048];
            process(std::str::from_utf8_mut(&mut buf[..]).unwrap_or_default())
        }
        _ => {
            let mut buf = [0u8; 512];
            process(std::str::from_utf8_mut(&mut buf[..]).unwrap_or_default())
        }
    }

    output
}

/// Get the content with proper encoding. Pass in a proper encoding label like SHIFT_JIS.
pub fn encode_bytes(html: &[u8], label: &str) -> String {
    match encoding_rs::Encoding::for_label(label.as_bytes()) {
        Some(enc) => decode_to_string(html, enc),
        _ => Default::default(),
    }
}

/// Get the content with proper encoding from a language. Pass in a proper language like "ja". This does nothing without the "encoding" flag.
pub fn encode_bytes_from_language(html: &[u8], language: &str) -> String {
    use encoding_rs::Encoding;

    let encoding = encoding_for_locale(language)
        .or_else(|| Encoding::for_bom(html).map(|(enc, _)| enc))
        .unwrap_or_else(|| {
            let mut detector = chardetng::EncodingDetector::new();
            detector.feed(html, false);
            detector.guess(None, true)
        });

    decode_to_string(html, encoding)
}

/// Get the content with proper encoding.
pub fn auto_encode_bytes(html: &[u8]) -> String {
    use encoding_rs::Encoding;

    if html.is_empty() {
        return String::new();
    }

    if let Some(encoding) = detect_encoding(html) {
        return encode_bytes(html, &encoding);
    }

    let encoding = Encoding::for_bom(html)
        .map(|(enc, _)| enc)
        .unwrap_or_else(|| {
            let mut detector = chardetng::EncodingDetector::new();
            detector.feed(html, false);
            detector.guess(None, true)
        });

    decode_to_string(html, encoding)
}

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

    #[test]
    fn test_detect_language() {
        use maud::{html, DOCTYPE};

        let page_title = "Readability Test";
        let page_h1 = "Reading is fun";

        let markup = html! {
            (DOCTYPE)
            meta charset="utf-8";
            title { (page_title) }
            h1 { (page_h1) }
            a href="spider.cloud";
            pre {
                r#"The content is ready for reading"#
            }
        }
        .into_string();

        assert_eq!(detect_language(markup.as_bytes()).is_none(), true);
    }
    #[test]
    fn test_encoding_for_locale() {
        assert_eq!(encoding_for_locale("en-us"), Some(encoding_rs::UTF_8));
        assert_eq!(encoding_for_locale("zh-cn"), Some(encoding_rs::GB18030));
        assert_eq!(encoding_for_locale("ja-jp"), Some(encoding_rs::SHIFT_JIS));
        assert_eq!(encoding_for_locale("ko-kr"), Some(encoding_rs::EUC_KR));
        assert!(encoding_for_locale("unknown-locale").is_none());
    }

    #[test]
    fn test_encoding_for_locale_case_insensitive() {
        assert_eq!(encoding_for_locale("EN-US"), Some(encoding_rs::UTF_8));
        assert_eq!(encoding_for_locale("Ja-Jp"), Some(encoding_rs::SHIFT_JIS));
        assert_eq!(encoding_for_locale("ZH-CN"), Some(encoding_rs::GB18030));
    }

    #[test]
    fn test_encoding_for_locale_long_input() {
        assert!(encoding_for_locale("this-is-a-very-long-locale-string-that-exceeds-the-buffer").is_none());
    }

    #[test]
    fn test_is_binary_file() {
        assert!(is_binary_file(&[0xFF, 0xD8, 0xFF]));
        assert!(is_binary_file(&[0x89, 0x50, 0x4E, 0x47]));
        assert!(is_binary_file(&[0x47, 0x49, 0x46, 0x38]));
        assert!(is_binary_file(&[0x42, 0x5A, 0x68]));
        assert!(!is_binary_file(&[0x00, 0x00, 0x00, 0x00]));
        assert!(!is_binary_file(&[0x01, 0x02, 0x03]));
    }

    #[test]
    fn test_is_binary_file_skips_leading_whitespace() {
        use crate::detect::is_binary_file_phf;

        // Aestiva HTML/OS-style padded HTML (the shape served by
        // seeleylake.com): nine leading newlines then `<!doctype html>`.
        // Must not be classified as binary.
        let padded = b"\n\n\n\n\n\n\n\n\n<!doctype html>\n<html></html>";
        assert!(!is_binary_file(padded));
        assert!(!is_binary_file_phf(padded));

        // Whitespace prefix in front of a real magic header still detects
        // the binary correctly.
        let mut padded_png = Vec::from(&b"  \t\r\n"[..]);
        padded_png.extend_from_slice(&[0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);
        assert!(is_binary_file(&padded_png));
        assert!(is_binary_file_phf(&padded_png));

        let mut padded_pdf = Vec::from(&b"\n\n"[..]);
        padded_pdf.extend_from_slice(b"%PDF-1.4\n");
        assert!(is_binary_file(&padded_pdf));
        assert!(is_binary_file_phf(&padded_pdf));

        // Whitespace-only / empty bodies are not binary.
        assert!(!is_binary_file(b""));
        assert!(!is_binary_file(b"   \t\n\r"));
        assert!(!is_binary_file_phf(b""));
        assert!(!is_binary_file_phf(b"   \t\n\r"));
    }

    #[test]
    fn test_encode_bytes() {
        let html_content = b"hello";
        let encoded = encode_bytes(html_content, "utf-8");
        assert_eq!(encoded, "hello");

        let html_content = b"\xa1Hola!";
        let encoded = encode_bytes(html_content, "windows-1252");
        assert_eq!(encoded, "\u{00a1}Hola!");

        let html_content = b"\x82\xA0";
        let encoded = encode_bytes(html_content, "shift_jis");
        assert_eq!(encoded, "\u{3042}");
    }

    #[test]
    fn test_encode_bytes_from_language() {
        let html_content = b"hello";
        let encoded = encode_bytes_from_language(html_content, "en-us");
        assert_eq!(encoded, "hello");

        let html_content = b"\xa1Hola!";
        let encoded = encode_bytes_from_language(html_content, "es-es");
        assert_eq!(encoded, "\u{00a1}Hola!");

        let html_content = b"\x82\xA0";
        let encoded = encode_bytes_from_language(html_content, "ja");
        assert_eq!(encoded, "\u{3042}");
    }

    #[test]
    fn test_find_subsequence() {
        let haystack = b"This is a simple test.";
        let needle = b"simple";
        assert_eq!(find_subsequence(haystack, needle), Some(10));

        let haystack = b"Another test case.";
        let needle = b"test";
        assert_eq!(find_subsequence(haystack, needle), Some(8));

        let haystack = b"No match here.";
        let needle = b"impossible";
        assert_eq!(find_subsequence(haystack, needle), None);
    }

    #[test]
    fn test_detect_language_with_html_lang_attribute() {
        let html_content =
            b"<html lang=\"en\"><head><title>Test</title></head><body></body></html>";
        assert_eq!(detect_language(html_content), Some("en".to_string()));
    }

    #[test]
    fn test_detect_language_without_lang_attribute() {
        let html_content = b"<html><head><title>Test</title></head><body></body></html>";
        assert!(detect_language(html_content).is_none());
    }

    #[test]
    fn test_detect_encoding_charset() {
        let html = br#"<!DOCTYPE html><meta charset="utf-8"><title>Test</title>"#;
        assert_eq!(
            detect_encoding(html).map(|s| s.to_lowercase()),
            Some("utf-8".to_string())
        );
    }

    #[test]
    fn test_detect_encoding_second_meta() {
        let html = br#"<meta name="viewport" content="width=device-width"><meta charset="shift_jis"><title>Test</title>"#;
        assert_eq!(
            detect_encoding(html).map(|s| s.to_lowercase()),
            Some("shift_jis".to_string())
        );
    }

    #[test]
    fn test_detect_encoding_http_equiv() {
        let html = br#"<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">"#;
        assert_eq!(
            detect_encoding(html),
            Some("iso-8859-1".to_string())
        );
    }

    #[test]
    fn test_detect_encoding_none() {
        let html = b"<html><head><title>No encoding</title></head></html>";
        assert_eq!(detect_encoding(html), None);
    }

    #[test]
    fn test_detect_html_metadata_both() {
        let html = br#"<html lang="fr"><head><meta charset="utf-8"></head></html>"#;
        let meta = detect::detect_html_metadata(html);
        assert!(meta.is_some());
        let meta = meta.unwrap();
        assert_eq!(meta.lang, Some("fr".to_string()));
        assert_eq!(meta.encoding.map(|s| s.to_lowercase()), Some("utf-8".to_string()));
    }

    #[test]
    fn test_detect_html_metadata_lang_only() {
        let html = br#"<html lang="de"><head><title>Test</title></head></html>"#;
        let meta = detect::detect_html_metadata(html).unwrap();
        assert_eq!(meta.lang, Some("de".to_string()));
        assert_eq!(meta.encoding, None);
    }

    #[test]
    fn test_detect_html_metadata_encoding_only() {
        let html = br#"<html><head><meta charset="euc-kr"></head></html>"#;
        let meta = detect::detect_html_metadata(html).unwrap();
        assert_eq!(meta.lang, None);
        assert_eq!(meta.encoding.map(|s| s.to_lowercase()), Some("euc-kr".to_string()));
    }

    #[test]
    fn test_auto_encode_bytes_empty() {
        assert_eq!(auto_encode_bytes(b""), "");
    }

    #[test]
    fn test_auto_encode_bytes_utf8() {
        let html = b"<meta charset=\"utf-8\">Hello world";
        let result = auto_encode_bytes(html);
        assert!(result.contains("Hello world"));
    }

    #[test]
    fn test_detect_language_unquoted() {
        let html = b"<html lang=en><head></head></html>";
        assert_eq!(detect_language(html), Some("en".to_string()));
    }

    #[test]
    fn test_detect_language_single_quotes() {
        let html = b"<html lang='ja'><head></head></html>";
        assert_eq!(detect_language(html), Some("ja".to_string()));
    }

    #[test]
    fn test_is_binary_file_empty() {
        assert!(!is_binary_file(&[]));
    }

    #[test]
    fn test_binary_detection_parity() {
        // Verify flattened MAGIC_TABLE matches PHF-based detection
        let test_cases: &[&[u8]] = &[
            &[0xFF, 0xD8, 0xFF],       // JPEG
            &[0x89, 0x50, 0x4E, 0x47], // PNG
            &[0x47, 0x49, 0x46, 0x38], // GIF
            &[0x42, 0x5A, 0x68],       // BZip
            &[0x42, 0x4D, 0x00],       // BMP
            &[0x50, 0x4B, 0x03, 0x04], // ZIP
            &[0x1F, 0x8B],             // GZIP
            &[0x7F, 0x45, 0x4C, 0x46], // ELF
            &[0xCA, 0xFE, 0xBA, 0xBE], // Java class
            &[0x25, 0x50, 0x44, 0x46], // PDF
            &[0x00, 0x00, 0x01, 0xBA], // MPEG
            &[0xFF, 0xFB],             // MP3
            &[0x49, 0x44, 0x33],       // MP3 ID3
            &[0x00, 0x00, 0x00, 0x00], // No match
            &[0x01, 0x02, 0x03],       // No match
            &[],                        // Empty
        ];
        for case in test_cases {
            assert_eq!(
                is_binary_file(case),
                detect::is_binary_file_phf(case),
                "Mismatch for {:?}",
                case
            );
        }
    }

    #[ignore]
    #[test]
    fn test_detect_encoding() {
        use maud::{html, DOCTYPE};
        let markup = html! {
            (DOCTYPE)
            meta charset="utf-8";
        }
        .into_string();
        assert!(
            detect_encoding(&markup.as_bytes())
                .unwrap_or_default()
                .to_lowercase()
                == "utf-8"
        );
    }
}