oxidize-pdf 2.5.0

//! Optimized PDF Reader with LRU caching
//!
//! This module provides an optimized version of PdfReader that uses
//! an LRU cache instead of unlimited HashMap caching to control memory usage.

use super::header::PdfHeader;
use super::object_stream::ObjectStream;
use super::objects::{PdfDictionary, PdfObject};
use super::stack_safe::StackSafeContext;
use super::trailer::PdfTrailer;
use super::xref::XRefTable;
use super::{ParseError, ParseOptions, ParseResult};
use crate::memory::{LruCache, MemoryOptions, MemoryStats};
use crate::objects::ObjectId;
use std::collections::HashMap;
use std::fs::File;
use std::io::{BufReader, Read, Seek, SeekFrom};
use std::path::Path;
use std::sync::Arc;

/// Optimized PDF reader with LRU caching
pub struct OptimizedPdfReader<R: Read + Seek> {
    reader: BufReader<R>,
    header: PdfHeader,
    xref: XRefTable,
    trailer: PdfTrailer,
    /// LRU cache for loaded objects
    object_cache: LruCache<ObjectId, Arc<PdfObject>>,
    /// Cache of object streams
    object_stream_cache: HashMap<u32, ObjectStream>,
    /// Page tree navigator
    #[allow(dead_code)]
    page_tree: Option<super::page_tree::PageTree>,
    /// Stack-safe parsing context
    #[allow(dead_code)]
    parse_context: StackSafeContext,
    /// Parsing options
    options: super::ParseOptions,
    /// Memory options
    #[allow(dead_code)]
    memory_options: MemoryOptions,
    /// Memory statistics
    memory_stats: MemoryStats,
}

impl<R: Read + Seek> OptimizedPdfReader<R> {
    /// Get parsing options
    pub fn options(&self) -> &super::ParseOptions {
        &self.options
    }

    /// Get memory statistics
    pub fn memory_stats(&self) -> &MemoryStats {
        &self.memory_stats
    }

    /// Clear the object cache
    pub fn clear_cache(&mut self) {
        self.object_cache.clear();
        self.object_stream_cache.clear();
        self.memory_stats.cached_objects = 0;
    }
}

impl OptimizedPdfReader<File> {
    /// Open a PDF file from a path with memory optimization
    pub fn open<P: AsRef<Path>>(path: P) -> ParseResult<Self> {
        let file = File::open(path)?;
        let options = super::ParseOptions::lenient();
        let memory_options = MemoryOptions::default();
        Self::new_with_options(file, options, memory_options)
    }

    /// Open a PDF file with custom memory options
    pub fn open_with_memory<P: AsRef<Path>>(
        path: P,
        memory_options: MemoryOptions,
    ) -> ParseResult<Self> {
        let file = File::open(path)?;
        let options = super::ParseOptions::lenient();
        Self::new_with_options(file, options, memory_options)
    }

    /// Open a PDF file with strict parsing
    pub fn open_strict<P: AsRef<Path>>(path: P) -> ParseResult<Self> {
        let file = File::open(path)?;
        let options = super::ParseOptions::strict();
        let memory_options = MemoryOptions::default();
        Self::new_with_options(file, options, memory_options)
    }
}

impl<R: Read + Seek> OptimizedPdfReader<R> {
    /// Create a new PDF reader from a reader
    pub fn new(reader: R) -> ParseResult<Self> {
        Self::new_with_options(
            reader,
            super::ParseOptions::default(),
            MemoryOptions::default(),
        )
    }

    /// Create a new PDF reader with custom parsing and memory options
    pub fn new_with_options(
        reader: R,
        options: super::ParseOptions,
        memory_options: MemoryOptions,
    ) -> ParseResult<Self> {
        let mut buf_reader = BufReader::new(reader);

        // Check if file is empty
        let start_pos = buf_reader.stream_position()?;
        buf_reader.seek(SeekFrom::End(0))?;
        let file_size = buf_reader.stream_position()?;
        buf_reader.seek(SeekFrom::Start(start_pos))?;

        if file_size == 0 {
            return Err(ParseError::EmptyFile);
        }

        // Parse header
        let header = PdfHeader::parse(&mut buf_reader)?;

        // Parse xref table
        let xref = XRefTable::parse_with_options(&mut buf_reader, &options)?;

        // Get trailer
        let trailer_dict = xref.trailer().ok_or(ParseError::InvalidTrailer)?.clone();

        let xref_offset = xref.xref_offset();
        let trailer = PdfTrailer::from_dict(trailer_dict, xref_offset)?;

        // Validate trailer
        trailer.validate()?;

        // Create LRU cache with configured size
        let cache_size = memory_options.cache_size.max(1);
        let object_cache = LruCache::new(cache_size);

        Ok(Self {
            reader: buf_reader,
            header,
            xref,
            trailer,
            object_cache,
            object_stream_cache: HashMap::new(),
            page_tree: None,
            parse_context: StackSafeContext::new(),
            options,
            memory_options,
            memory_stats: MemoryStats::default(),
        })
    }

    /// Get the PDF version
    pub fn version(&self) -> &super::header::PdfVersion {
        &self.header.version
    }

    /// Get the document catalog
    pub fn catalog(&mut self) -> ParseResult<&PdfDictionary> {
        // Try to get root from trailer
        let (obj_num, gen_num) = match self.trailer.root() {
            Ok(root) => root,
            Err(_) => {
                // If Root is missing, try fallback methods
                #[cfg(debug_assertions)]
                tracing::debug!("Warning: Trailer missing Root entry, attempting recovery");

                // First try the fallback method
                if let Some(root) = self.trailer.find_root_fallback() {
                    root
                } else {
                    // Last resort: scan for Catalog object
                    if let Ok(catalog_ref) = self.find_catalog_object() {
                        catalog_ref
                    } else {
                        return Err(ParseError::MissingKey("Root".to_string()));
                    }
                }
            }
        };

        let catalog = self.get_object(obj_num, gen_num)?;

        catalog.as_dict().ok_or_else(|| ParseError::SyntaxError {
            position: 0,
            message: "Catalog is not a dictionary".to_string(),
        })
    }

    /// Get the document info dictionary
    pub fn info(&mut self) -> ParseResult<Option<&PdfDictionary>> {
        match self.trailer.info() {
            Some((obj_num, gen_num)) => {
                let info = self.get_object(obj_num, gen_num)?;
                Ok(info.as_dict())
            }
            None => Ok(None),
        }
    }

    /// Get an object by reference
    pub fn get_object(&mut self, obj_num: u32, gen_num: u16) -> ParseResult<&PdfObject> {
        let object_id = ObjectId::new(obj_num, gen_num);

        // Check LRU cache first
        if let Some(cached_obj) = self.object_cache.get(&object_id) {
            self.memory_stats.cache_hits += 1;
            // Convert Arc<PdfObject> to &PdfObject
            // This is safe because we maintain the Arc in the cache
            let ptr = Arc::as_ptr(cached_obj);
            return Ok(unsafe { &*ptr });
        }

        self.memory_stats.cache_misses += 1;

        // Load object from disk
        let obj = self.load_object_from_disk(obj_num, gen_num)?;

        // Store in LRU cache
        let arc_obj = Arc::new(obj);
        self.object_cache.put(object_id, arc_obj);
        self.memory_stats.cached_objects = self.object_cache.len();

        // Return reference to cached object
        // The Arc is owned by the cache, so we can safely return a reference
        // We need to get it from the cache to ensure lifetime
        self.object_cache
            .get(&object_id)
            .map(|arc| unsafe { &*Arc::as_ptr(arc) })
            .ok_or(ParseError::SyntaxError {
                position: 0,
                message: "Object not in cache after insertion".to_string(),
            })
    }

    /// Internal method to load an object from disk
    fn load_object_from_disk(&mut self, obj_num: u32, gen_num: u16) -> ParseResult<PdfObject> {
        // Check if this is a compressed object
        if let Some(ext_entry) = self.xref.get_extended_entry(obj_num) {
            if let Some((stream_obj_num, index_in_stream)) = ext_entry.compressed_info {
                // This is a compressed object - need to extract from object stream
                return self.get_compressed_object_direct(
                    obj_num,
                    gen_num,
                    stream_obj_num,
                    index_in_stream,
                );
            }
        }

        // Get xref entry
        let entry = self
            .xref
            .get_entry(obj_num)
            .ok_or(ParseError::InvalidReference(obj_num, gen_num))?;

        if !entry.in_use {
            // Free object
            return Ok(PdfObject::Null);
        }

        if entry.generation != gen_num {
            return Err(ParseError::InvalidReference(obj_num, gen_num));
        }

        // Seek to object position
        self.reader.seek(std::io::SeekFrom::Start(entry.offset))?;

        // Parse object header (obj_num gen_num obj)
        let mut lexer =
            super::lexer::Lexer::new_with_options(&mut self.reader, self.options.clone());

        // Read object number with recovery
        let token = lexer.next_token()?;
        let read_obj_num = match token {
            super::lexer::Token::Integer(n) => n as u32,
            _ => {
                // Try fallback recovery
                if self.options.lenient_syntax {
                    if self.options.collect_warnings {
                        tracing::debug!(
                            "Warning: Using expected object number {obj_num} instead of parsed token"
                        );
                    }
                    obj_num
                } else {
                    return Err(ParseError::SyntaxError {
                        position: entry.offset as usize,
                        message: "Expected object number".to_string(),
                    });
                }
            }
        };

        if read_obj_num != obj_num && !self.options.lenient_syntax {
            return Err(ParseError::SyntaxError {
                position: entry.offset as usize,
                message: format!(
                    "Object number mismatch: expected {obj_num}, found {read_obj_num}"
                ),
            });
        }

        // Read generation number
        let token = lexer.next_token()?;
        let read_gen_num = match token {
            super::lexer::Token::Integer(n) => n as u16,
            _ => {
                if self.options.lenient_syntax {
                    if self.options.collect_warnings {
                        tracing::debug!(
                            "Warning: Using generation 0 instead of parsed token for object {obj_num}"
                        );
                    }
                    0
                } else {
                    return Err(ParseError::SyntaxError {
                        position: entry.offset as usize,
                        message: "Expected generation number".to_string(),
                    });
                }
            }
        };

        if read_gen_num != gen_num && !self.options.lenient_syntax {
            return Err(ParseError::SyntaxError {
                position: entry.offset as usize,
                message: format!(
                    "Generation number mismatch: expected {gen_num}, found {read_gen_num}"
                ),
            });
        }

        // Read 'obj' keyword
        let token = lexer.next_token()?;
        match token {
            super::lexer::Token::Obj => {}
            _ => {
                if self.options.lenient_syntax {
                    if self.options.collect_warnings {
                        tracing::debug!("Warning: Missing 'obj' keyword for object {obj_num}");
                    }
                } else {
                    return Err(ParseError::SyntaxError {
                        position: entry.offset as usize,
                        message: "Expected 'obj' keyword".to_string(),
                    });
                }
            }
        }

        // Parse the object
        let object = PdfObject::parse(&mut lexer)?;

        // Skip 'endobj' if present
        if let Ok(token) = lexer.peek_token() {
            if let super::lexer::Token::EndObj = token {
                let _ = lexer.next_token();
            } else if !self.options.lenient_syntax && self.options.collect_warnings {
                tracing::debug!("Warning: Missing 'endobj' for object {obj_num}");
            }
        }

        Ok(object)
    }

    /// Get a compressed object directly (returns owned object)
    fn get_compressed_object_direct(
        &mut self,
        obj_num: u32,
        _gen_num: u16,
        stream_obj_num: u32,
        _index_in_stream: u32,
    ) -> ParseResult<PdfObject> {
        // First get the object stream
        if !self.object_stream_cache.contains_key(&stream_obj_num) {
            // Load the stream object
            let stream_obj = self.load_object_from_disk(stream_obj_num, 0)?;

            if let PdfObject::Stream(stream) = stream_obj {
                let obj_stream = ObjectStream::parse(stream, &ParseOptions::default())?;
                self.object_stream_cache.insert(stream_obj_num, obj_stream);
            } else {
                return Err(ParseError::SyntaxError {
                    position: 0,
                    message: "Object stream is not a stream object".to_string(),
                });
            }
        }

        // Get object from stream
        let obj_stream = self
            .object_stream_cache
            .get(&stream_obj_num)
            .ok_or_else(|| ParseError::SyntaxError {
                position: 0,
                message: "Object stream not found in cache".to_string(),
            })?;

        obj_stream
            .get_object(obj_num)
            .cloned()
            .ok_or(ParseError::InvalidReference(obj_num, 0))
    }

    /// Find catalog object by scanning (fallback method)
    fn find_catalog_object(&mut self) -> ParseResult<(u32, u16)> {
        // This is a simplified implementation
        // In a real scenario, we would scan through objects to find the catalog
        for obj_num in 1..100 {
            if let Ok(PdfObject::Dictionary(dict)) = self.get_object(obj_num, 0) {
                if let Some(PdfObject::Name(type_name)) = dict.get("Type") {
                    if type_name.0.as_bytes() == b"Catalog" {
                        return Ok((obj_num, 0));
                    }
                }
            }
        }
        Err(ParseError::MissingKey("Catalog".to_string()))
    }

    /// Get a reference to the inner reader
    pub fn reader(&mut self) -> &mut BufReader<R> {
        &mut self.reader
    }
}

/// Helper function to get memory usage info for a PdfObject
pub fn estimate_object_size(obj: &PdfObject) -> usize {
    match obj {
        PdfObject::Null => 8,
        PdfObject::Boolean(_) => 16,
        PdfObject::Integer(_) => 16,
        PdfObject::Real(_) => 16,
        PdfObject::String(s) => 24 + s.as_bytes().len(),
        PdfObject::Name(n) => 24 + n.0.len(),
        PdfObject::Array(arr) => {
            24 + arr.len() * 8 + arr.0.iter().map(estimate_object_size).sum::<usize>()
        }
        PdfObject::Dictionary(dict) => {
            24 + dict.0.len() * 16
                + dict
                    .0
                    .iter()
                    .map(|(k, v)| k.0.len() + estimate_object_size(v))
                    .sum::<usize>()
        }
        PdfObject::Stream(s) => {
            48 + s.data.len() + estimate_object_size(&PdfObject::Dictionary(s.dict.clone()))
        }
        PdfObject::Reference(_, _) => 16,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::parser::objects::{PdfArray, PdfDictionary, PdfName, PdfStream, PdfString};
    use std::io::Cursor;

    fn create_minimal_pdf() -> Vec<u8> {
        // Offsets calculated from actual file:
        // Header: 0-9
        // Object 1: 9-58   (offset: 0000000009)
        // Object 2: 58-115 (offset: 0000000058)
        // Object 3: 115-186 (offset: 0000000115)
        // XRef table: 186 (startxref: 186)
        b"%PDF-1.4\n\
1 0 obj\n\
<< /Type /Catalog /Pages 2 0 R >>\n\
endobj\n\
2 0 obj\n\
<< /Type /Pages /Kids [3 0 R] /Count 1 >>\n\
endobj\n\
3 0 obj\n\
<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] >>\n\
endobj\n\
xref\n\
0 4\n\
0000000000 65535 f \n\
0000000009 00000 n \n\
0000000058 00000 n \n\
0000000115 00000 n \n\
trailer\n\
<< /Size 4 /Root 1 0 R >>\n\
startxref\n\
186\n\
%%EOF\n"
            .to_vec()
    }

    fn create_empty_pdf() -> Vec<u8> {
        Vec::new()
    }

    fn create_invalid_pdf() -> Vec<u8> {
        b"Not a PDF file".to_vec()
    }

    #[test]
    fn test_memory_options_integration() {
        let options = MemoryOptions::default().with_cache_size(100);
        assert_eq!(options.cache_size, 100);

        let options = MemoryOptions::default().with_cache_size(0);
        assert_eq!(options.cache_size, 0);
    }

    #[test]
    fn test_object_size_estimation_basic_types() {
        // Null
        let obj = PdfObject::Null;
        assert_eq!(estimate_object_size(&obj), 8);

        // Boolean
        let obj = PdfObject::Boolean(true);
        assert_eq!(estimate_object_size(&obj), 16);

        let obj = PdfObject::Boolean(false);
        assert_eq!(estimate_object_size(&obj), 16);

        // Integer
        let obj = PdfObject::Integer(42);
        assert_eq!(estimate_object_size(&obj), 16);

        let obj = PdfObject::Integer(-1000);
        assert_eq!(estimate_object_size(&obj), 16);

        // Real
        let obj = PdfObject::Real(3.14159);
        assert_eq!(estimate_object_size(&obj), 16);

        // Reference
        let obj = PdfObject::Reference(5, 0);
        assert_eq!(estimate_object_size(&obj), 16);
    }

    #[test]
    fn test_object_size_estimation_string_types() {
        // Empty string
        let obj = PdfObject::String(PdfString::new(b"".to_vec()));
        assert_eq!(estimate_object_size(&obj), 24);

        // Short string
        let obj = PdfObject::String(PdfString::new(b"Hello".to_vec()));
        assert_eq!(estimate_object_size(&obj), 24 + 5);

        // Long string
        let long_text = "A".repeat(1000);
        let obj = PdfObject::String(PdfString::new(long_text.as_bytes().to_vec()));
        assert_eq!(estimate_object_size(&obj), 24 + 1000);

        // Name objects
        let obj = PdfObject::Name(PdfName::new("Type".to_string()));
        assert_eq!(estimate_object_size(&obj), 24 + 4);

        let obj = PdfObject::Name(PdfName::new("".to_string()));
        assert_eq!(estimate_object_size(&obj), 24);
    }

    #[test]
    fn test_object_size_estimation_array() {
        // Empty array
        let obj = PdfObject::Array(PdfArray(vec![]));
        assert_eq!(estimate_object_size(&obj), 24);

        // Simple array
        let obj = PdfObject::Array(PdfArray(vec![
            PdfObject::Integer(1),
            PdfObject::Integer(2),
            PdfObject::Integer(3),
        ]));
        assert_eq!(estimate_object_size(&obj), 24 + 3 * 8 + 3 * 16);

        // Nested array
        let inner_array = PdfObject::Array(PdfArray(vec![
            PdfObject::Integer(10),
            PdfObject::Integer(20),
        ]));
        let obj = PdfObject::Array(PdfArray(vec![PdfObject::Integer(1), inner_array]));
        let expected = 24 + 2 * 8 + 16 + (24 + 2 * 8 + 2 * 16);
        assert_eq!(estimate_object_size(&obj), expected);
    }

    #[test]
    fn test_object_size_estimation_dictionary() {
        // Empty dictionary
        let obj = PdfObject::Dictionary(PdfDictionary::new());
        assert_eq!(estimate_object_size(&obj), 24);

        // Simple dictionary
        let mut dict = PdfDictionary::new();
        dict.insert(
            "Type".to_string(),
            PdfObject::Name(PdfName::new("Catalog".to_string())),
        );
        dict.insert("Count".to_string(), PdfObject::Integer(5));

        let obj = PdfObject::Dictionary(dict);
        let expected = 24 + 2 * 16 + (4 + 24 + 7) + (5 + 16);
        assert_eq!(estimate_object_size(&obj), expected);
    }

    #[test]
    fn test_object_size_estimation_stream() {
        let mut dict = PdfDictionary::new();
        dict.insert("Length".to_string(), PdfObject::Integer(10));

        let stream = PdfObject::Stream(PdfStream {
            dict: dict.clone(),
            data: b"Hello Test".to_vec(),
        });

        let dict_size = estimate_object_size(&PdfObject::Dictionary(dict));
        let expected = 48 + 10 + dict_size;
        assert_eq!(estimate_object_size(&stream), expected);
    }

    #[test]
    fn test_object_size_estimation_complex_structure() {
        // Complex nested structure
        let mut inner_dict = PdfDictionary::new();
        inner_dict.insert(
            "Font".to_string(),
            PdfObject::Name(PdfName::new("Helvetica".to_string())),
        );
        inner_dict.insert("Size".to_string(), PdfObject::Integer(12));

        let array = PdfObject::Array(PdfArray(vec![
            PdfObject::String(PdfString::new(b"Text content".to_vec())),
            PdfObject::Dictionary(inner_dict),
            PdfObject::Reference(10, 0),
        ]));

        let mut main_dict = PdfDictionary::new();
        main_dict.insert(
            "Type".to_string(),
            PdfObject::Name(PdfName::new("Page".to_string())),
        );
        main_dict.insert("Contents".to_string(), array);

        let obj = PdfObject::Dictionary(main_dict);

        // The size should be > 0 and reasonable
        let size = estimate_object_size(&obj);
        assert!(size > 100);
        assert!(size < 1000);
    }

    #[test]
    fn test_optimized_reader_empty_file() {
        let data = create_empty_pdf();
        let cursor = Cursor::new(data);

        let result = OptimizedPdfReader::new(cursor);
        assert!(result.is_err());
        if let Err(ParseError::EmptyFile) = result {
            // Expected error
        } else {
            panic!("Expected EmptyFile error");
        }
    }

    #[test]
    fn test_optimized_reader_invalid_file() {
        let data = create_invalid_pdf();
        let cursor = Cursor::new(data);

        let result = OptimizedPdfReader::new(cursor);
        assert!(result.is_err());
        // Should fail during header parsing
    }

    #[test]
    fn test_optimized_reader_creation_with_options() {
        let data = create_minimal_pdf();
        let cursor = Cursor::new(data);

        let parse_options = ParseOptions {
            lenient_syntax: true,
            collect_warnings: false,
            ..Default::default()
        };

        let memory_options = MemoryOptions::default().with_cache_size(50);

        let result = OptimizedPdfReader::new_with_options(cursor, parse_options, memory_options);
        if result.is_err() {
            // Skip test if PDF parsing fails due to incomplete implementation
            return;
        }

        let reader = result.unwrap();
        assert!(reader.options().lenient_syntax);
        assert!(!reader.options().collect_warnings);
    }

    #[test]
    fn test_optimized_reader_version_access() {
        let data = create_minimal_pdf();
        let cursor = Cursor::new(data);

        let result = OptimizedPdfReader::new(cursor);
        if result.is_err() {
            // Skip test if PDF parsing fails
            return;
        }

        let reader = result.unwrap();
        let version = reader.version();

        // Should have parsed version from %PDF-1.4
        assert_eq!(version.major, 1);
        assert_eq!(version.minor, 4);
    }

    #[test]
    fn test_memory_options_validation() {
        let data = create_minimal_pdf();
        let cursor = Cursor::new(data);

        // Test that cache size of 0 gets converted to 1
        let memory_options = MemoryOptions::default().with_cache_size(0);
        let parse_options = ParseOptions::default();

        let result = OptimizedPdfReader::new_with_options(cursor, parse_options, memory_options);
        if result.is_err() {
            // The memory option validation should still work even if PDF parsing fails
            let memory_opts = MemoryOptions::default().with_cache_size(0);
            let cache_size = memory_opts.cache_size.max(1);
            assert_eq!(cache_size, 1);
        }
    }

    #[test]
    fn test_estimate_object_size_edge_cases() {
        // Very large array
        let large_array = PdfObject::Array(PdfArray((0..1000).map(PdfObject::Integer).collect()));
        let size = estimate_object_size(&large_array);
        assert!(size > 16000); // Should be substantial

        // Very large dictionary
        let mut large_dict = PdfDictionary::new();
        for i in 0..100 {
            large_dict.insert(
                format!("Key{i}"),
                PdfObject::String(PdfString::new(format!("Value{i}").as_bytes().to_vec())),
            );
        }
        let obj = PdfObject::Dictionary(large_dict);
        let size = estimate_object_size(&obj);
        assert!(size > 1000);
    }

    #[test]
    fn test_memory_options_default_values() {
        let options = MemoryOptions::default();

        // Verify reasonable defaults
        assert!(options.cache_size > 0);
        assert!(options.cache_size < 10000); // Should be reasonable
    }

    #[test]
    fn test_memory_options_builder_pattern() {
        let options = MemoryOptions::default().with_cache_size(500);

        assert_eq!(options.cache_size, 500);
    }

    #[test]
    fn test_object_size_estimation_consistency() {
        // Same objects should have same size
        let obj1 = PdfObject::String(PdfString::new(b"Test".to_vec()));
        let obj2 = PdfObject::String(PdfString::new(b"Test".to_vec()));

        assert_eq!(estimate_object_size(&obj1), estimate_object_size(&obj2));

        // Different content should have different sizes
        let obj3 = PdfObject::String(PdfString::new(b"Different".to_vec()));
        assert_ne!(estimate_object_size(&obj1), estimate_object_size(&obj3));
    }

    #[test]
    fn test_object_size_estimation_zero_values() {
        // Integer zero
        let obj = PdfObject::Integer(0);
        assert_eq!(estimate_object_size(&obj), 16);

        // Real zero
        let obj = PdfObject::Real(0.0);
        assert_eq!(estimate_object_size(&obj), 16);

        // Reference zero
        let obj = PdfObject::Reference(0, 0);
        assert_eq!(estimate_object_size(&obj), 16);
    }

    #[test]
    fn test_object_size_estimation_negative_values() {
        let obj = PdfObject::Integer(-42);
        assert_eq!(estimate_object_size(&obj), 16);

        let obj = PdfObject::Real(-3.14159);
        assert_eq!(estimate_object_size(&obj), 16);
    }

    #[test]
    fn test_object_size_estimation_unicode_strings() {
        // Unicode string
        let unicode_text = "Hello 世界 🌍";
        let obj = PdfObject::String(PdfString::new(unicode_text.as_bytes().to_vec()));
        let expected_size = 24 + unicode_text.len();
        assert_eq!(estimate_object_size(&obj), expected_size);
    }

    #[test]
    fn test_object_size_estimation_mixed_array() {
        let obj = PdfObject::Array(PdfArray(vec![
            PdfObject::Null,
            PdfObject::Boolean(true),
            PdfObject::Integer(42),
            PdfObject::Real(3.14),
            PdfObject::String(PdfString::new(b"test".to_vec())),
            PdfObject::Name(PdfName::new("Name".to_string())),
            PdfObject::Reference(1, 0),
        ]));

        let expected = 24 + 7 * 8 + 8 + 16 + 16 + 16 + (24 + 4) + (24 + 4) + 16;
        assert_eq!(estimate_object_size(&obj), expected);
    }

    #[test]
    fn test_find_catalog_object_range() {
        // Test that find_catalog_object scans a reasonable range
        // This is mainly testing the logic bounds - it scans objects 1-99
        let data = create_minimal_pdf();
        let cursor = Cursor::new(data);

        // We can't easily test the actual scanning without a real PDF,
        // but we can verify the implementation exists and has reasonable bounds
        if let Ok(mut reader) = OptimizedPdfReader::new(cursor) {
            // The method exists and should scan objects 1-99
            // In a real test with proper PDF, this would find the catalog
            let _result = reader.find_catalog_object();
            // Result depends on the actual PDF content, so we don't assert specific outcomes
        }
    }

    #[test]
    fn test_memory_stats_tracking() {
        // Test that memory stats are properly initialized
        let data = create_minimal_pdf();
        let cursor = Cursor::new(data);

        if let Ok(reader) = OptimizedPdfReader::new(cursor) {
            // Memory stats should be initialized
            assert_eq!(reader.memory_stats.cache_hits, 0);
            assert_eq!(reader.memory_stats.cache_misses, 0);
            assert_eq!(reader.memory_stats.cached_objects, 0);
        }
    }

    // =============================================================================
    // RIGOROUS TESTS FOR OPTIMIZED READER
    // =============================================================================

    mod rigorous {
        use super::*;

        #[test]
        fn test_lru_cache_hit_tracking() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let mut reader =
                OptimizedPdfReader::new(cursor).expect("Minimal PDF must parse successfully");

            // Initial state: 0 hits, 0 misses
            assert_eq!(
                reader.memory_stats().cache_hits,
                0,
                "Cache hits must start at 0"
            );
            assert_eq!(
                reader.memory_stats().cache_misses,
                0,
                "Cache misses must start at 0"
            );

            // First access: should be cache miss
            let _ = reader.get_object(1, 0);
            assert_eq!(
                reader.memory_stats().cache_misses,
                1,
                "First access must be cache miss"
            );
            assert_eq!(reader.memory_stats().cache_hits, 0, "No cache hits yet");

            // Second access: should be cache hit
            let _ = reader.get_object(1, 0);
            assert_eq!(
                reader.memory_stats().cache_hits,
                1,
                "Second access must be cache hit"
            );
            assert_eq!(
                reader.memory_stats().cache_misses,
                1,
                "Cache misses unchanged"
            );

            // Third access: another cache hit
            let _ = reader.get_object(1, 0);
            assert_eq!(
                reader.memory_stats().cache_hits,
                2,
                "Third access must increment cache hits"
            );
        }

        #[test]
        fn test_lru_cache_capacity_enforcement() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            // Create reader with small cache (size 2)
            let memory_options = MemoryOptions::default().with_cache_size(2);
            let parse_options = ParseOptions::default();

            let mut reader =
                OptimizedPdfReader::new_with_options(cursor, parse_options, memory_options)
                    .expect("Minimal PDF must parse successfully");

            // Load object 1 (cache size: 1)
            let _ = reader.get_object(1, 0);
            assert_eq!(
                reader.memory_stats().cached_objects,
                1,
                "Cache should have 1 object"
            );

            // Load object 2 (cache size: 2)
            let _ = reader.get_object(2, 0);
            assert_eq!(
                reader.memory_stats().cached_objects,
                2,
                "Cache should have 2 objects"
            );

            // Load object 3 (cache size: still 2, evicts LRU)
            let _ = reader.get_object(3, 0);
            assert_eq!(
                reader.memory_stats().cached_objects,
                2,
                "Cache must not exceed capacity of 2"
            );
        }

        #[test]
        fn test_cache_clear_resets_stats() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let mut reader =
                OptimizedPdfReader::new(cursor).expect("Minimal PDF must parse successfully");

            // Load some objects
            let _ = reader.get_object(1, 0);
            let _ = reader.get_object(1, 0); // cache hit

            // Verify stats before clear
            assert!(reader.memory_stats().cache_hits > 0);
            assert!(reader.memory_stats().cached_objects > 0);

            // Clear cache
            reader.clear_cache();

            // Cached objects should be 0 after clear
            assert_eq!(
                reader.memory_stats().cached_objects,
                0,
                "Cache should be empty after clear"
            );

            // Stats for hits/misses remain (cumulative)
            // But next access will be miss
            let _ = reader.get_object(1, 0);
            assert!(
                reader.memory_stats().cache_misses >= 2,
                "Access after clear must be cache miss"
            );
        }

        #[test]
        fn test_empty_file_error_handling() {
            let data = create_empty_pdf();
            let cursor = Cursor::new(data);

            let result = OptimizedPdfReader::new(cursor);

            assert!(result.is_err(), "Empty file must return error");
            match result {
                Err(ParseError::EmptyFile) => {
                    // Expected specific error type
                }
                Err(other) => panic!("Expected EmptyFile error, got: {:?}", other),
                Ok(_) => panic!("Should not succeed with empty file"),
            }
        }

        #[test]
        fn test_invalid_header_error_handling() {
            let data = create_invalid_pdf();
            let cursor = Cursor::new(data);

            let result = OptimizedPdfReader::new(cursor);

            assert!(result.is_err(), "Invalid PDF must return error");
            // Error should occur during header parsing
        }

        #[test]
        fn test_version_parsing_exact_values() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let reader =
                OptimizedPdfReader::new(cursor).expect("Minimal PDF must parse successfully");

            let version = reader.version();

            // Minimal PDF is version 1.4
            assert_eq!(version.major, 1, "PDF major version must be 1");
            assert_eq!(version.minor, 4, "PDF minor version must be 4");
        }

        #[test]
        fn test_options_accessibility() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let parse_options = ParseOptions {
                lenient_syntax: true,
                collect_warnings: false,
                ..Default::default()
            };
            let memory_options = MemoryOptions::default().with_cache_size(100);

            let reader =
                OptimizedPdfReader::new_with_options(cursor, parse_options, memory_options)
                    .expect("Minimal PDF must parse successfully");

            let opts = reader.options();

            assert_eq!(
                opts.lenient_syntax, true,
                "Options must match provided values"
            );
            assert_eq!(
                opts.collect_warnings, false,
                "Options must match provided values"
            );
        }

        #[test]
        fn test_catalog_access_requires_valid_trailer() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let mut reader =
                OptimizedPdfReader::new(cursor).expect("Minimal PDF must parse successfully");

            // Catalog should be accessible
            let catalog_result = reader.catalog();

            if catalog_result.is_ok() {
                let catalog = catalog_result.unwrap();

                // Catalog must be a dictionary with Type = Catalog
                assert_eq!(
                    catalog.get("Type"),
                    Some(&PdfObject::Name(PdfName("Catalog".to_string()))),
                    "Catalog must have /Type /Catalog"
                );
            } else {
                // If catalog fails, should be specific error
                assert!(matches!(
                    catalog_result.unwrap_err(),
                    ParseError::MissingKey(_) | ParseError::SyntaxError { .. }
                ));
            }
        }

        #[test]
        fn test_info_none_when_absent() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let mut reader =
                OptimizedPdfReader::new(cursor).expect("Minimal PDF must parse successfully");

            let info_result = reader.info();

            if info_result.is_ok() {
                let info = info_result.unwrap();
                // Minimal PDF has no Info dictionary in trailer
                assert!(
                    info.is_none(),
                    "Info should be None when not present in trailer"
                );
            }
        }

        #[test]
        fn test_get_object_wrong_generation() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let mut reader =
                OptimizedPdfReader::new(cursor).expect("Minimal PDF must parse successfully");

            // Object 1 0 exists, but try accessing with wrong generation
            let result = reader.get_object(1, 5); // Wrong generation number

            // Should either return error or Null for free object
            if result.is_err() {
                assert!(matches!(
                    result.unwrap_err(),
                    ParseError::InvalidReference(_, _)
                ));
            }
        }

        #[test]
        fn test_get_nonexistent_object() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let mut reader =
                OptimizedPdfReader::new(cursor).expect("Minimal PDF must parse successfully");

            // Try accessing object that doesn't exist
            let result = reader.get_object(9999, 0);

            assert!(
                result.is_err(),
                "Accessing nonexistent object must return error"
            );
            assert!(matches!(
                result.unwrap_err(),
                ParseError::InvalidReference(_, _)
            ));
        }

        #[test]
        fn test_memory_options_min_cache_size() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            // Even with cache_size = 0, implementation enforces minimum of 1
            let memory_options = MemoryOptions::default().with_cache_size(0);
            let parse_options = ParseOptions::default();

            let mut reader =
                OptimizedPdfReader::new_with_options(cursor, parse_options, memory_options)
                    .expect("Minimal PDF must parse successfully");

            // Should be able to cache at least 1 object
            let _ = reader.get_object(1, 0);
            assert_eq!(
                reader.memory_stats().cached_objects,
                1,
                "Must cache at least 1 object even with cache_size=0"
            );
        }

        #[test]
        fn test_estimate_object_size_exact_values() {
            // Test exact size calculations for primitive types

            // Null: 8 bytes
            assert_eq!(estimate_object_size(&PdfObject::Null), 8);

            // Boolean: 16 bytes
            assert_eq!(estimate_object_size(&PdfObject::Boolean(true)), 16);
            assert_eq!(estimate_object_size(&PdfObject::Boolean(false)), 16);

            // Integer: 16 bytes
            assert_eq!(estimate_object_size(&PdfObject::Integer(0)), 16);
            assert_eq!(estimate_object_size(&PdfObject::Integer(42)), 16);
            assert_eq!(estimate_object_size(&PdfObject::Integer(-1000)), 16);

            // Real: 16 bytes
            assert_eq!(estimate_object_size(&PdfObject::Real(0.0)), 16);
            assert_eq!(estimate_object_size(&PdfObject::Real(3.14159)), 16);

            // Reference: 16 bytes
            assert_eq!(estimate_object_size(&PdfObject::Reference(1, 0)), 16);
            assert_eq!(estimate_object_size(&PdfObject::Reference(999, 5)), 16);
        }

        #[test]
        fn test_estimate_string_size_formula() {
            // String size = 24 + byte_length

            // Empty string
            let empty = PdfObject::String(PdfString::new(vec![]));
            assert_eq!(estimate_object_size(&empty), 24);

            // 10 bytes
            let ten_bytes = PdfObject::String(PdfString::new(b"0123456789".to_vec()));
            assert_eq!(estimate_object_size(&ten_bytes), 24 + 10);

            // 100 bytes
            let hundred_bytes = PdfObject::String(PdfString::new(vec![b'X'; 100]));
            assert_eq!(estimate_object_size(&hundred_bytes), 24 + 100);
        }

        #[test]
        fn test_estimate_array_size_formula() {
            // Array size = 24 + (len * 8) + sum(element sizes)

            // Empty array: 24
            let empty = PdfObject::Array(PdfArray(vec![]));
            assert_eq!(estimate_object_size(&empty), 24);

            // 3 integers: 24 + (3*8) + (3*16) = 24 + 24 + 48 = 96
            let three_ints = PdfObject::Array(PdfArray(vec![
                PdfObject::Integer(1),
                PdfObject::Integer(2),
                PdfObject::Integer(3),
            ]));
            assert_eq!(estimate_object_size(&three_ints), 24 + 24 + 48);
        }

        #[test]
        fn test_estimate_dictionary_size_formula() {
            // Dictionary size = 24 + (len * 16) + sum(key_len + value_size)

            // Empty dict: 24
            let empty = PdfObject::Dictionary(PdfDictionary::new());
            assert_eq!(estimate_object_size(&empty), 24);

            // Single entry: 24 + 16 + ("Type".len + Name("Page").size)
            let mut dict = PdfDictionary::new();
            dict.insert(
                "Type".to_string(),
                PdfObject::Name(PdfName::new("Page".to_string())),
            );
            let obj = PdfObject::Dictionary(dict);
            let expected = 24 + 16 + 4 + (24 + 4); // key_len=4, name_size=24+4
            assert_eq!(estimate_object_size(&obj), expected);
        }

        #[test]
        fn test_cache_isolation_between_instances() {
            let data = create_minimal_pdf();

            // Create two independent readers
            let cursor1 = Cursor::new(data.clone());
            let cursor2 = Cursor::new(data);

            let mut reader1 =
                OptimizedPdfReader::new(cursor1).expect("Minimal PDF must parse successfully");
            let mut reader2 =
                OptimizedPdfReader::new(cursor2).expect("Minimal PDF must parse successfully");

            // Load object in reader1
            let _ = reader1.get_object(1, 0);
            assert_eq!(reader1.memory_stats().cached_objects, 1);

            // reader2 should have independent cache (empty)
            assert_eq!(
                reader2.memory_stats().cached_objects,
                0,
                "Readers must have independent caches"
            );

            // Load in reader2
            let _ = reader2.get_object(1, 0);
            assert_eq!(
                reader2.memory_stats().cached_objects,
                1,
                "reader2 cache should now have 1 object"
            );
            assert_eq!(
                reader1.memory_stats().cached_objects,
                1,
                "reader1 cache unchanged"
            );
        }

        #[test]
        fn test_reader_with_strict_options() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let parse_options = ParseOptions::strict();
            let memory_options = MemoryOptions::default();

            let reader =
                OptimizedPdfReader::new_with_options(cursor, parse_options, memory_options)
                    .expect("Minimal PDF must parse successfully");

            let opts = reader.options();
            assert_eq!(
                opts.strict_mode, true,
                "Strict options must have strict_mode=true"
            );
        }

        #[test]
        fn test_reader_with_lenient_options() {
            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let parse_options = ParseOptions::lenient();
            let memory_options = MemoryOptions::default();

            let reader =
                OptimizedPdfReader::new_with_options(cursor, parse_options, memory_options)
                    .expect("Minimal PDF must parse successfully");

            let opts = reader.options();
            assert_eq!(
                opts.strict_mode, false,
                "Lenient options must have strict_mode=false"
            );
        }

        // =============================================================================
        // COVERAGE EXPANSION: Tests for open*() functions (previously uncovered)
        // =============================================================================

        #[test]
        fn test_open_from_file_path() {
            use std::io::Write;
            use tempfile::NamedTempFile;

            // Create temp PDF file
            let mut temp_file = NamedTempFile::new().expect("Failed to create temp file");
            temp_file
                .write_all(&create_minimal_pdf())
                .expect("Failed to write PDF data");

            let path = temp_file.path();

            // Test open() function
            let result = OptimizedPdfReader::open(path);

            assert!(result.is_ok(), "open() must succeed with valid PDF file");

            let reader = result.unwrap();

            // Verify it's using lenient options
            assert_eq!(
                reader.options().strict_mode,
                false,
                "open() must use lenient parsing"
            );

            // Verify version was parsed correctly
            assert_eq!(reader.version().major, 1);
            assert_eq!(reader.version().minor, 4);
        }

        #[test]
        fn test_open_with_memory_options() {
            use std::io::Write;
            use tempfile::NamedTempFile;

            let mut temp_file = NamedTempFile::new().expect("Failed to create temp file");
            temp_file
                .write_all(&create_minimal_pdf())
                .expect("Failed to write PDF data");

            let path = temp_file.path();

            // Custom memory options with small cache
            let memory_options = MemoryOptions::default().with_cache_size(10);

            // Test open_with_memory() function
            let result = OptimizedPdfReader::open_with_memory(path, memory_options);

            assert!(result.is_ok(), "open_with_memory() must succeed");

            let mut reader = result.unwrap();

            // Verify lenient parsing
            assert_eq!(reader.options().strict_mode, false);

            // Verify cache works with custom size
            let _ = reader.get_object(1, 0);
            assert_eq!(
                reader.memory_stats().cached_objects,
                1,
                "Cache should respect custom memory options"
            );
        }

        #[test]
        fn test_open_strict_mode() {
            use std::io::Write;
            use tempfile::NamedTempFile;

            let mut temp_file = NamedTempFile::new().expect("Failed to create temp file");
            temp_file
                .write_all(&create_minimal_pdf())
                .expect("Failed to write PDF data");

            let path = temp_file.path();

            // Test open_strict() function
            let result = OptimizedPdfReader::open_strict(path);

            assert!(result.is_ok(), "open_strict() must succeed with valid PDF");

            let reader = result.unwrap();

            // Verify strict mode is enabled
            assert_eq!(
                reader.options().strict_mode,
                true,
                "open_strict() must use strict parsing"
            );

            // Verify version parsing still works
            assert_eq!(reader.version().major, 1);
            assert_eq!(reader.version().minor, 4);
        }

        #[test]
        fn test_open_nonexistent_file() {
            use std::path::PathBuf;

            // Try to open file that doesn't exist
            let path = PathBuf::from("/tmp/this_file_does_not_exist_xyz_123.pdf");

            let result = OptimizedPdfReader::open(&path);

            assert!(result.is_err(), "open() must fail with nonexistent file");

            // Should get IO error (file not found)
            match result {
                Err(ParseError::Io(_)) => {
                    // Expected error type
                }
                Err(other) => panic!("Expected IO error, got: {:?}", other),
                Ok(_) => panic!("Should not succeed with nonexistent file"),
            }
        }

        #[test]
        fn test_load_object_from_disk_free_object() {
            // This tests the "free object" path in load_object_from_disk
            // We need a PDF with a free entry in xref

            // PDF with free object at position 0
            let pdf_with_free = b"%PDF-1.4\n\
1 0 obj\n\
<< /Type /Catalog /Pages 2 0 R >>\n\
endobj\n\
2 0 obj\n\
<< /Type /Pages /Kids [3 0 R] /Count 1 >>\n\
endobj\n\
3 0 obj\n\
<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] >>\n\
endobj\n\
xref\n\
0 4\n\
0000000000 65535 f \n\
0000000009 00000 n \n\
0000000058 00000 n \n\
0000000115 00000 n \n\
trailer\n\
<< /Size 4 /Root 1 0 R >>\n\
startxref\n\
186\n\
%%EOF\n"
                .to_vec();

            let cursor = Cursor::new(pdf_with_free);
            let mut reader =
                OptimizedPdfReader::new(cursor).expect("PDF with free object must parse");

            // Try to get object 0 (free object)
            let result = reader.get_object(0, 65535);

            // Free objects return Null (not an error)
            if let Ok(obj) = result {
                assert!(
                    matches!(obj, PdfObject::Null),
                    "Free object should return Null"
                );
            }
        }

        #[test]
        fn test_find_catalog_when_trailer_missing_root() {
            // Test the fallback catalog finding logic
            // This is tested indirectly through catalog() function

            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            let mut reader = OptimizedPdfReader::new(cursor).expect("Minimal PDF must parse");

            // catalog() should use find_catalog_object if Root is missing
            let result = reader.catalog();

            // With valid minimal PDF, catalog should be found
            if let Ok(catalog) = result {
                assert_eq!(
                    catalog.get("Type"),
                    Some(&PdfObject::Name(PdfName("Catalog".to_string()))),
                    "Catalog must have /Type /Catalog"
                );
            }
        }

        #[test]
        fn test_load_object_generation_mismatch_strict() {
            // Test that strict mode rejects generation number mismatches
            // Use a properly formatted PDF with correct xref but intentionally
            // request wrong generation number

            let data = create_minimal_pdf();
            let cursor = Cursor::new(data);

            // Create with STRICT options
            let parse_options = ParseOptions::strict();
            let memory_options = MemoryOptions::default();

            let mut reader =
                OptimizedPdfReader::new_with_options(cursor, parse_options, memory_options)
                    .expect("Minimal PDF must parse in strict mode");

            // Object 1 exists with generation 0
            // Try to access with wrong generation number (5) in strict mode
            let result = reader.get_object(1, 5);

            // In strict mode, should get InvalidReference error
            assert!(
                result.is_err(),
                "Strict mode must reject generation number mismatch"
            );

            if let Err(e) = result {
                assert!(
                    matches!(e, ParseError::InvalidReference(_, _)),
                    "Expected InvalidReference error, got: {:?}",
                    e
                );
            }
        }
    }
}