xberg 1.2.9

//! Per-section validation functions.
//!
//! This module contains validation functions for individual configuration sections
//! and their specific parameters. Each function validates a specific aspect of
//! the configuration and returns detailed error messages when validation fails.

use crate::{Result, XbergError};

/// Valid binarization methods for image preprocessing.
const VALID_BINARIZATION_METHODS: &[&str] = &["none", "off", "otsu", "adaptive", "sauvola"];

/// Valid token reduction levels.
const VALID_TOKEN_REDUCTION_LEVELS: &[&str] = &["off", "light", "moderate", "aggressive", "maximum"];

/// Valid OCR backends.
///
/// Every name a backend registers under must appear here, or config validation rejects a backend
/// the registry is perfectly capable of serving. The list is deliberately not feature-gated: the
/// entries already present (`sceptre`, `vlm`, `paddle-ocr`) are feature-gated backends too, and a
/// name that is valid-but-not-compiled-in is reported by backend resolution with a message about
/// the missing feature, which is more useful than "invalid OCR backend".
const VALID_OCR_BACKENDS: &[&str] = &[
    "tesseract",
    "paddleocr",
    "paddle-ocr",
    "sceptre",
    "vlm",
    "candle-trocr",
    "candle-paddleocr-vl",
    "candle-glm-ocr",
    "candle-deepseek-ocr",
];

/// Common ISO 639-1 language codes (extended list).
/// Covers most major languages and variants used in document processing.
const VALID_LANGUAGE_CODES: &[&str] = &[
    "en",
    "de",
    "fr",
    "es",
    "it",
    "pt",
    "nl",
    "pl",
    "ru",
    "zh",
    "ja",
    "ko",
    "bg",
    "cs",
    "da",
    "el",
    "et",
    "fi",
    "hu",
    "lt",
    "lv",
    "ro",
    "sk",
    "sl",
    "sv",
    "uk",
    "ar",
    "hi",
    "th",
    "tr",
    "vi",
    "eng",
    "deu",
    "fra",
    "spa",
    "ita",
    "por",
    "nld",
    "pol",
    "rus",
    "zho",
    "jpn",
    "jpn_vert",
    "kor",
    "ces",
    "dan",
    "ell",
    "est",
    "fin",
    "hun",
    "lit",
    "lav",
    "ron",
    "slk",
    "slv",
    "swe",
    "tur",
    "ch",
    "chinese_cht",
    "latin",
    "cyrillic",
    "english",
    "japanese",
    "korean",
    "telugu",
    "kannada",
    "chinese-simplified",
    "simplified-chinese",
    "devanagari",
    "arabic",
    // ISO codes and established aliases accepted by the Sceptre backend that are
    // not already covered above. Keep this feature-independent for config parsing. ~keep
    "af",
    "afr",
    "az",
    "aze",
    "bel",
    "be",
    "bul",
    "bs",
    "bos",
    "ca",
    "cat",
    "cy",
    "cym",
    "cze",
    "wel",
    "ger",
    "fre",
    "ga",
    "fil",
    "gle",
    "hr",
    "hrv",
    "id",
    "ind",
    "is",
    "isl",
    "ice",
    "kk",
    "kaz",
    "ky",
    "kir",
    "mk",
    "mkd",
    "mac",
    "mn",
    "mon",
    "mi",
    "mri",
    "mao",
    "ms",
    "msa",
    "may",
    "mt",
    "mlt",
    "dut",
    "no",
    "nor",
    "rum",
    "slo",
    "sq",
    "sqi",
    "alb",
    "sr",
    "srp",
    "sw",
    "swa",
    "tl",
    "tg",
    "tgk",
    "ukr",
    "uz",
    "uzb",
    "vie",
    "ku",
    "kur",
    "la",
    "lat",
    "oc",
    "oci",
    "pi",
    "pli",
    "te",
    "tel",
    "kn",
    "kan",
    "abq",
    "ady",
    "kbd",
    "ava",
    "dar",
    "inh",
    "che",
    "lbe",
    "lez",
    "tab",
    "tjk",
    "ch_sim",
    "ch-sim",
    "rs_latin",
    "rs-latin",
    "rs_cyrillic",
    "rs-cyrillic",
    "jpn-vert",
    "sr-latn",
    "srp-latn",
    "sr-cyrl",
    "srp-cyrl",
    "zh-cn",
    "zh-hans",
    "chi",
    "chs",
];

/// Canonical set of Tesseract-supported ISO 639-3 traineddata language codes.
///
/// This is the single source of truth for which codes Tesseract can OCR with. It lives here,
/// feature-independent, rather than in `ocr::validation` (which is gated behind `feature = "ocr"`
/// and would otherwise not exist for a build that compiles `OcrConfig` without the `ocr` feature).
/// `ocr::validation::TESSERACT_SUPPORTED_LANGUAGE_CODES` builds its lookup set from this exact
/// array instead of maintaining a second hardcoded copy — two independently maintained allowlists
/// silently drifted apart before (GH#1621: `fao` was Tesseract-supported but missing here), and a
/// single array that both call sites read from makes that drift impossible. ~keep
pub(crate) const TESSERACT_LANGUAGE_CODES: &[&str] = &[
    "afr", "amh", "ara", "asm", "aze", "aze_cyrl", "bel", "ben", "bod", "bos", "bre", "bul", "cat", "ceb", "ces",
    "chi_sim", "chi_tra", "chr", "cos", "cym", "dan", "deu", "div", "dzo", "ell", "eng", "enm", "epo", "equ", "est",
    "eus", "fao", "fas", "fil", "fin", "fra", "frk", "frm", "fry", "gla", "gle", "glg", "grc", "guj", "hat", "heb",
    "hin", "hrv", "hun", "hye", "iku", "ind", "isl", "ita", "ita_old", "jav", "jpn", "kan", "kat", "kat_old", "kaz",
    "khm", "kir", "kmr", "kor", "lao", "lat", "lav", "lit", "ltz", "mal", "mar", "mkd", "mlt", "mon", "mri", "msa",
    "mya", "nep", "nld", "nor", "oci", "ori", "osd", "pan", "pol", "por", "pus", "que", "ron", "rus", "san", "sin",
    "slk", "slv", "snd", "spa", "spa_old", "sqi", "srp", "srp_latn", "sun", "swa", "swe", "syr", "tam", "tat", "tel",
    "tgk", "tha", "tir", "ton", "tur", "uig", "ukr", "urd", "uzb", "uzb_cyrl", "vie", "yid", "yor",
];

/// Valid tesseract PSM (Page Segmentation Mode) values.
///
/// 0 is deliberately absent. Tesseract's PSM 0 is `PSM_OSD_ONLY` -- orientation and script
/// detection with no character recognition at all -- so it cannot serve a text-extraction
/// request. Accepting it produced an empty document with a success exit code (GH#1586). ~keep
const VALID_TESSERACT_PSM: &[i32] = &[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13];

/// Valid tesseract OEM (OCR Engine Mode) values.
const VALID_TESSERACT_OEM: &[i32] = &[0, 1, 2, 3];

/// Valid output formats for document extraction.
/// Supports plain text, markdown, djot, HTML, JSON, and structured output formats.
/// "json" and "structured" are distinct formats, not aliases of each other.
/// Also accepts aliases: "text" for "plain", "md" for "markdown", "structured-ocr" for "structured".
#[cfg(test)]
const VALID_OUTPUT_FORMATS: &[&str] = &["plain", "text", "markdown", "md", "djot", "html", "structured", "json"];

/// Validate a binarization method string.
///
/// # Arguments
///
/// * `method` - The binarization method to validate (e.g., "none", "otsu", "adaptive", "sauvola")
///
/// # Returns
///
/// `Ok(())` if the method is valid, or a `ValidationError` with details about valid options.
///
/// # Examples
///
/// Not run as a doctest: `pub(crate)`, so it is unreachable from a downstream crate.
///
/// ```ignore
/// use xberg::core::config_validation::validate_binarization_method;
///
/// assert!(validate_binarization_method("none").is_ok());
/// assert!(validate_binarization_method("otsu").is_ok());
/// assert!(validate_binarization_method("adaptive").is_ok());
/// assert!(validate_binarization_method("invalid").is_err());
/// ```
pub(crate) fn validate_binarization_method(method: &str) -> Result<()> {
    let method = method.to_lowercase();
    if VALID_BINARIZATION_METHODS.contains(&method.as_str()) {
        Ok(())
    } else {
        Err(XbergError::Validation {
            message: format!(
                "Invalid binarization method '{}'. Valid options are: {}",
                method,
                VALID_BINARIZATION_METHODS.join(", ")
            ),
            source: None,
        })
    }
}

pub(crate) fn validate_image_preprocessing_config(config: &crate::types::ImagePreprocessingConfig) -> Result<()> {
    validate_binarization_method(&config.binarization_method)?;
    let method = config.binarization_method.to_ascii_lowercase();
    if matches!(method.as_str(), "none" | "off") && config.deskew {
        return Err(XbergError::Validation {
            message: "deskew must be false when binarization_method is none or off".to_string(),
            source: None,
        });
    }
    Ok(())
}

/// Validate a token reduction level string.
///
/// # Arguments
///
/// * `level` - The token reduction level to validate (e.g., "off", "light", "moderate")
///
/// # Returns
///
/// `Ok(())` if the level is valid, or a `ValidationError` with details about valid options.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_token_reduction_level;
///
/// assert!(validate_token_reduction_level("off").is_ok());
/// assert!(validate_token_reduction_level("moderate").is_ok());
/// assert!(validate_token_reduction_level("extreme").is_err());
/// ```
pub(crate) fn validate_token_reduction_level(level: &str) -> Result<()> {
    let level = level.to_lowercase();
    if VALID_TOKEN_REDUCTION_LEVELS.contains(&level.as_str()) {
        Ok(())
    } else {
        Err(XbergError::Validation {
            message: format!(
                "Invalid token reduction level '{}'. Valid options are: {}",
                level,
                VALID_TOKEN_REDUCTION_LEVELS.join(", ")
            ),
            source: None,
        })
    }
}

/// Validate an OCR backend string.
///
/// # Arguments
///
/// * `backend` - The OCR backend to validate (e.g., "tesseract", "paddleocr")
///
/// # Returns
///
/// `Ok(())` if the backend is valid, or a `ValidationError` with details about valid options.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_ocr_backend;
///
/// assert!(validate_ocr_backend("tesseract").is_ok());
/// assert!(validate_ocr_backend("paddleocr").is_ok());
/// assert!(validate_ocr_backend("invalid").is_err());
/// ```
pub(crate) fn validate_ocr_backend(backend: &str) -> Result<()> {
    let normalized = backend.to_lowercase();
    if VALID_OCR_BACKENDS.contains(&normalized.as_str()) || is_registered_ocr_backend(backend) {
        Ok(())
    } else {
        Err(XbergError::Validation {
            message: format!(
                "Invalid OCR backend '{}'. Valid options are: {}, or the name of a backend \
                 registered through `register_ocr_backend`",
                normalized,
                VALID_OCR_BACKENDS.join(", ")
            ),
            source: None,
        })
    }
}

/// Whether `backend` names a plugin backend registered through `register_ocr_backend`.
///
/// `VALID_OCR_BACKENDS` lists only the built-ins, so consulting it alone rejected every
/// third-party backend. That became reachable once `ExtractionConfig::validate` was wired into
/// `extract`/`extract_batch`, which made the plugin OCR backend feature unusable: a registered
/// custom backend was refused before extraction ever started. Matched case-insensitively so a
/// registered name behaves like the built-in list. ~keep
fn is_registered_ocr_backend(backend: &str) -> bool {
    crate::plugins::registry::get_ocr_backend_registry()
        .read()
        .list()
        .iter()
        .any(|name| name.eq_ignore_ascii_case(backend))
}

/// Validate a language code (ISO 639-1 or 639-3 format).
///
/// Accepts both 2-letter ISO 639-1 codes (e.g., "en", "de") and
/// 3-letter ISO 639-3 codes (e.g., "eng", "deu") for broader compatibility.
///
/// # Arguments
///
/// * `code` - The language code to validate
///
/// # Returns
///
/// `Ok(())` if the code is valid, or a `ValidationError` indicating an invalid language code.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_language_code;
///
/// assert!(validate_language_code("en").is_ok());
/// assert!(validate_language_code("eng").is_ok());
/// assert!(validate_language_code("de").is_ok());
/// assert!(validate_language_code("deu").is_ok());
/// assert!(validate_language_code("invalid").is_err());
/// ```
#[cfg_attr(alef, alef(skip))]
pub(crate) fn validate_language_code(code: &str) -> Result<()> {
    let code_lower = code.to_lowercase();
    let code_normalized = code_lower.replace('_', "-");

    if code_lower == "all" || code_lower == "*" {
        return Ok(());
    }

    if VALID_LANGUAGE_CODES.contains(&code_lower.as_str())
        || VALID_LANGUAGE_CODES.contains(&code_normalized.as_str())
        || TESSERACT_LANGUAGE_CODES.contains(&code_lower.as_str())
        || TESSERACT_LANGUAGE_CODES.contains(&code_normalized.as_str())
    {
        return Ok(());
    }

    Err(XbergError::Validation {
        message: format!(
            "Invalid language code '{}'. Use ISO 639-1 (2-letter, e.g., 'en', 'de') \
             or ISO 639-3 (3-letter, e.g., 'eng', 'deu') codes. \
             Common codes: en, de, fr, es, it, pt, nl, pl, ru, zh, ja, ko, ar, hi, th.",
            code
        ),
        source: None,
    })
}

/// Validate a tesseract Page Segmentation Mode (PSM).
///
/// # Arguments
///
/// * `psm` - The PSM value to validate (1-13; 0 is OSD-only and is rejected)
///
/// # Returns
///
/// `Ok(())` if the PSM is valid, or a `ValidationError` with details about valid ranges.
///
/// # Examples
///
/// Not run as a doctest: `pub(crate)`, so it is unreachable from a downstream crate.
///
/// ```ignore
/// use xberg::core::config_validation::validate_tesseract_psm;
///
/// assert!(validate_tesseract_psm(3).is_ok());  // Fully automatic
/// assert!(validate_tesseract_psm(6).is_ok());  // Single block of text
/// assert!(validate_tesseract_psm(14).is_err()); // Out of range
/// assert!(validate_tesseract_psm(0).is_err());  // OSD-only: recognises no text
/// ```
pub(crate) fn validate_tesseract_psm(psm: i32) -> Result<()> {
    if VALID_TESSERACT_PSM.contains(&psm) {
        return Ok(());
    }
    let message = if psm == 0 {
        "Invalid tesseract PSM value '0'. PSM 0 is orientation and script detection (OSD) only: \
         it performs no character recognition, so extraction returns no text. \
         Use 3 (auto), 6 (single block), or 11 (sparse text); omit `psm` to let the pipeline choose."
            .to_string()
    } else {
        format!(
            "Invalid tesseract PSM value '{}'. Valid range is 1-13. \
             Common values: 3 (auto), 6 (single block), 11 (sparse text).",
            psm
        )
    };
    Err(XbergError::Validation { message, source: None })
}

/// Validate a tesseract OCR Engine Mode (OEM).
///
/// # Arguments
///
/// * `oem` - The OEM value to validate (0-3)
///
/// # Returns
///
/// `Ok(())` if the OEM is valid, or a `ValidationError` with details about valid options.
///
/// # Examples
///
/// Not run as a doctest: `pub(crate)`, so it is unreachable from a downstream crate.
///
/// ```ignore
/// use xberg::core::config_validation::validate_tesseract_oem;
///
/// assert!(validate_tesseract_oem(1).is_ok());  // Neural nets (LSTM)
/// assert!(validate_tesseract_oem(2).is_ok());  // Legacy + LSTM
/// assert!(validate_tesseract_oem(4).is_err()); // Out of range
/// ```
pub(crate) fn validate_tesseract_oem(oem: i32) -> Result<()> {
    if VALID_TESSERACT_OEM.contains(&oem) {
        Ok(())
    } else {
        Err(XbergError::Validation {
            message: format!(
                "Invalid tesseract OEM value '{}'. Valid range is 0-3. \
                 0=Legacy, 1=LSTM, 2=Legacy+LSTM, 3=Default",
                oem
            ),
            source: None,
        })
    }
}

/// Validate a document extraction output format.
///
/// Accepts the following formats and aliases:
/// - "plain" or "text" for plain text output
/// - "markdown" or "md" for Markdown output
/// - "djot" for Djot markup format
/// - "html" for HTML output
///
/// # Arguments
///
/// * `format` - The output format to validate
///
/// # Returns
///
/// `Ok(())` if the format is valid, or a `ValidationError` with details about valid options.
///
/// # Examples
///
/// Not run as a doctest: `pub(crate)`, so it is unreachable from a downstream crate.
///
/// ```ignore
/// use xberg::core::config_validation::validate_output_format;
///
/// assert!(validate_output_format("text").is_ok());
/// assert!(validate_output_format("plain").is_ok());
/// assert!(validate_output_format("markdown").is_ok());
/// assert!(validate_output_format("md").is_ok());
/// assert!(validate_output_format("djot").is_ok());
/// assert!(validate_output_format("html").is_ok());
/// assert!(validate_output_format("json").is_ok());
/// ```
#[cfg(test)]
pub(crate) fn validate_output_format(format: &str) -> Result<()> {
    let format = format.to_lowercase();
    if VALID_OUTPUT_FORMATS.contains(&format.as_str()) {
        Ok(())
    } else {
        Err(XbergError::Validation {
            message: format!(
                "Invalid output format '{}'. Valid options are: {}",
                format,
                VALID_OUTPUT_FORMATS.join(", ")
            ),
            source: None,
        })
    }
}

/// Validate a confidence threshold value.
///
/// Confidence thresholds should be between 0.0 and 1.0 inclusive.
///
/// # Arguments
///
/// * `confidence` - The confidence threshold to validate
///
/// # Returns
///
/// `Ok(())` if the confidence is valid, or a `ValidationError` with details about valid ranges.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_confidence;
///
/// assert!(validate_confidence(0.5).is_ok());
/// assert!(validate_confidence(0.0).is_ok());
/// assert!(validate_confidence(1.0).is_ok());
/// assert!(validate_confidence(1.5).is_err());
/// assert!(validate_confidence(-0.1).is_err());
/// ```
pub(crate) fn validate_confidence(confidence: f64) -> Result<()> {
    if (0.0..=1.0).contains(&confidence) {
        Ok(())
    } else {
        Err(XbergError::Validation {
            message: format!(
                "Invalid confidence threshold '{}'. Must be between 0.0 and 1.0.",
                confidence
            ),
            source: None,
        })
    }
}

/// Validate a DPI (dots per inch) value.
///
/// DPI should be a positive integer, typically 72-600.
///
/// # Arguments
///
/// * `dpi` - The DPI value to validate
///
/// # Returns
///
/// `Ok(())` if the DPI is valid, or a `ValidationError` with details about valid ranges.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_dpi;
///
/// assert!(validate_dpi(96).is_ok());
/// assert!(validate_dpi(300).is_ok());
/// assert!(validate_dpi(0).is_err());
/// assert!(validate_dpi(-1).is_err());
/// ```
pub(crate) fn validate_dpi(dpi: i32) -> Result<()> {
    if dpi > 0 && dpi <= 2400 {
        Ok(())
    } else {
        Err(XbergError::Validation {
            message: format!(
                "Invalid DPI value '{}'. Must be a positive integer, typically 72-600.",
                dpi
            ),
            source: None,
        })
    }
}

/// Validate chunk size parameters.
///
/// Checks that max_chars > 0 and max_overlap < max_chars.
///
/// # Arguments
///
/// * `max_chars` - The maximum characters per chunk
/// * `max_overlap` - The maximum overlap between chunks
///
/// # Returns
///
/// `Ok(())` if the parameters are valid, or a `ValidationError` with details about constraints.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_chunking_params;
///
/// assert!(validate_chunking_params(1000, 200).is_ok());
/// assert!(validate_chunking_params(500, 50).is_ok());
/// assert!(validate_chunking_params(0, 100).is_err()); // max_chars must be > 0
/// assert!(validate_chunking_params(100, 150).is_err()); // overlap >= max_chars
/// ```
pub(crate) fn validate_chunking_params(max_chars: usize, max_overlap: usize) -> Result<()> {
    if max_chars == 0 {
        return Err(XbergError::Validation {
            message: "max_chars must be greater than 0".to_string(),
            source: None,
        });
    }

    if max_overlap >= max_chars {
        return Err(XbergError::Validation {
            message: format!(
                "max_overlap ({}) must be less than max_chars ({})",
                max_overlap, max_chars
            ),
            source: None,
        });
    }

    Ok(())
}

/// Validate that an [`LlmConfig`](crate::core::config::LlmConfig) has a non-empty model string.
///
/// # Arguments
///
/// * `model` - The model string to validate
///
/// # Returns
///
/// `Ok(())` if the model is non-empty, or a `ValidationError` otherwise.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_llm_config_model;
///
/// assert!(validate_llm_config_model("openai/gpt-4o").is_ok());
/// assert!(validate_llm_config_model("").is_err());
/// ```
pub(crate) fn validate_llm_config_model(model: &str) -> Result<()> {
    if model.trim().is_empty() {
        return Err(XbergError::Validation {
            message: "LLM config 'model' must not be empty. Provide a model identifier (e.g., 'openai/gpt-4o')."
                .to_string(),
            source: None,
        });
    }
    Ok(())
}

/// Validate a CSV delimiter string.
///
/// The delimiter must be exactly one ASCII byte (e.g. `","`, `";"`, `"\t"`,
/// `"|"`). An empty string or a value containing a multi-byte UTF-8
/// character (e.g. `"é"` or a multi-character string) is rejected.
///
/// # Arguments
///
/// * `delimiter` - The delimiter string to validate
///
/// # Returns
///
/// `Ok(())` if the delimiter is a single ASCII byte, or a `ValidationError` otherwise.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_csv_delimiter;
///
/// assert!(validate_csv_delimiter(";").is_ok());
/// assert!(validate_csv_delimiter("").is_err());
/// assert!(validate_csv_delimiter(",,").is_err());
/// assert!(validate_csv_delimiter("é").is_err());
/// ```
pub(crate) fn validate_csv_delimiter(delimiter: &str) -> Result<()> {
    if delimiter.len() == 1 && delimiter.is_ascii() {
        Ok(())
    } else {
        Err(XbergError::Validation {
            message: format!(
                "Invalid CSV delimiter '{}'. Must be exactly one ASCII character (e.g. ',', ';', '\\t', '|').",
                delimiter
            ),
            source: None,
        })
    }
}

/// Whether enabling layout detection while `output_format` stays [`crate::OutputFormat::Plain`]
/// wastes the layout pass.
///
/// Layout detection exists to feed the structured-reconstruction pipeline that turns
/// detected regions into headings, lists and tables. At [`crate::OutputFormat::Plain`] no renderer
/// consumes that structure — the layout model still runs (measured: 20s on tesseract, 202s
/// on paddle, for a 16-page scan) and every region it detects is discarded. This implements
/// point 4 of the documented OCR/layout contract: "layout enabled implies output should be
/// structured, never plain."
///
/// This is a pure predicate meant to back a *warning*, not a validation error and not a
/// coercion: `Plain` stays the default output format and layout stays off by default, so a
/// caller combining both deliberately is still free to do so. Pass the fully resolved values
/// (after every override has been applied), not raw CLI flags.
///
/// # Arguments
///
/// * `layout_enabled` - Whether layout detection will run for this extraction.
/// * `output_format` - The resolved output format the extraction will render.
///
/// # Returns
///
/// `true` when layout is enabled and the output format is [`crate::OutputFormat::Plain`] — the
/// layout work will be computed and its structure discarded.
///
/// # Examples
///
/// ```
/// use xberg::core::config_validation::layout_wastes_plain_output;
/// use xberg::OutputFormat;
///
/// assert!(layout_wastes_plain_output(true, &OutputFormat::Plain));
/// assert!(!layout_wastes_plain_output(true, &OutputFormat::Markdown));
/// assert!(!layout_wastes_plain_output(false, &OutputFormat::Plain));
/// ```
#[cfg_attr(alef, alef(skip))]
pub fn layout_wastes_plain_output(layout_enabled: bool, output_format: &crate::OutputFormat) -> bool {
    layout_enabled && *output_format == crate::OutputFormat::Plain
}

/// Validate that a VLM OCR backend has the required `vlm_config`.
///
/// When the OCR backend is set to `"vlm"`, the `vlm_config` field must be present
/// to provide the model endpoint configuration, and the model string must be non-empty.
///
/// # Arguments
///
/// * `backend` - The OCR backend name
/// * `vlm_config` - The optional VLM config to validate
///
/// # Returns
///
/// `Ok(())` if the backend is not `"vlm"` or `vlm_config` is present with a valid model,
/// or a `ValidationError` if `"vlm"` backend is used without `vlm_config` or with an empty model.
///
/// # Examples
///
/// ```ignore
/// use xberg::core::config_validation::validate_vlm_backend_config;
/// use xberg::core::config::LlmConfig;
///
/// assert!(validate_vlm_backend_config("tesseract", None).is_ok());
/// let config = LlmConfig {
///     model: "openai/gpt-4o".to_string(),
///     api_key: None,
///     base_url: None,
///     timeout_secs: None,
///     max_retries: None,
///     temperature: None,
///     max_tokens: None,
/// };
/// assert!(validate_vlm_backend_config("vlm", Some(&config)).is_ok());
/// assert!(validate_vlm_backend_config("vlm", None).is_err());
/// ```
pub(crate) fn validate_vlm_backend_config(
    backend: &str,
    vlm_config: Option<&crate::core::config::LlmConfig>,
) -> Result<()> {
    if backend.to_lowercase() == "vlm" {
        match vlm_config {
            None => {
                return Err(XbergError::Validation {
                    message: "OCR backend 'vlm' requires 'vlm_config' to be set with model endpoint configuration."
                        .to_string(),
                    source: None,
                });
            }
            Some(config) => {
                validate_llm_config_model(&config.model)?;
            }
        }
    }
    Ok(())
}