picojson 0.2.3

// SPDX-License-Identifier: Apache-2.0

use crate::event_processor::{EscapeTiming, ParserCore};
use crate::parse_error::ParseError;
use crate::shared::{Event, PullParser};
use crate::slice_content_builder::SliceContentBuilder;
use crate::slice_input_buffer::InputBuffer;
use crate::ujson;

use ujson::{BitStackConfig, DefaultConfig};

/// A pull parser that parses JSON from a slice.
///
/// Generic over BitStack storage type for configurable nesting depth.
// Lifetime 'a is the input buffer lifetime
// lifetime 'b is the scratch/copy buffer lifetime
pub struct SliceParser<'a, 'b, C: BitStackConfig = DefaultConfig> {
    /// The shared parser core that handles the unified event processing loop
    parser_core: ParserCore<C::Bucket, C::Counter>,
    /// The content builder that handles SliceParser-specific content extraction
    content_builder: SliceContentBuilder<'a, 'b>,
}

/// Methods for the pull parser.
impl<'a> SliceParser<'a, '_, DefaultConfig> {
    /// Creates a new parser for the given JSON input.
    ///
    /// This parser assumes no string escapes will be encountered. If escapes are found,
    /// parsing will fail with `ScratchBufferFull` error.
    ///
    /// For JSON with potential string escapes, use `with_buffer()` instead.
    ///
    /// # Arguments
    /// * `input` - A string slice containing the JSON data to be parsed.
    ///
    /// # Example
    /// ```
    /// use picojson::SliceParser;
    /// let parser = SliceParser::new(r#"{"name": "value"}"#);
    /// ```
    pub fn new(input: &'a str) -> Self {
        Self::new_from_slice(input.as_bytes())
    }

    /// Creates a new parser from a byte slice.
    ///
    /// Assumes no string escapes will be encountered. For JSON with escapes, use [`with_buffer_from_slice`].
    ///
    /// # Example
    /// ```
    /// # use picojson::SliceParser;
    /// let parser = SliceParser::new_from_slice(br#"{"name": "value"}"#);
    /// ```
    ///
    /// [`with_buffer_from_slice`]: Self::with_buffer_from_slice
    pub fn new_from_slice(input: &'a [u8]) -> Self {
        Self::with_config_from_slice(input)
    }
}

/// Constructor with scratch buffer for SliceParser using DefaultConfig
impl<'a, 'b> SliceParser<'a, 'b, DefaultConfig> {
    /// Creates a new parser for the given JSON input with external scratch buffer.
    ///
    /// Use this when your JSON contains string escapes (like `\n`, `\"`, `\u0041`) that
    /// need to be unescaped during parsing.
    ///
    /// # Arguments
    /// * `input` - A string slice containing the JSON data to be parsed.
    /// * `scratch_buffer` - A mutable byte slice for temporary string unescaping operations.
    ///   This buffer needs to be at least as long as the longest
    ///   contiguous token (string, key, number) in the input.
    ///
    /// # Example
    /// ```
    /// use picojson::SliceParser;
    /// let mut scratch = [0u8; 1024];
    /// let parser = SliceParser::with_buffer(r#"{"msg": "Hello\nWorld"}"#, &mut scratch);
    /// ```
    pub fn with_buffer(input: &'a str, scratch_buffer: &'b mut [u8]) -> Self {
        Self::with_buffer_from_slice(input.as_bytes(), scratch_buffer)
    }

    /// Creates a new parser from a byte slice with a scratch buffer.
    ///
    /// Use when JSON contains string escapes that need unescaping.
    ///
    /// # Example
    /// ```
    /// # use picojson::SliceParser;
    /// let mut scratch = [0u8; 1024];
    /// let parser = SliceParser::with_buffer_from_slice(br#"{"msg": "Hello\nWorld"}"#, &mut scratch);
    /// ```
    pub fn with_buffer_from_slice(input: &'a [u8], scratch_buffer: &'b mut [u8]) -> Self {
        Self::with_config_and_buffer_from_slice(input, scratch_buffer)
    }
}

/// Generic constructor for SliceParser with custom configurations
impl<'a, 'b, C: BitStackConfig> SliceParser<'a, 'b, C> {
    /// Creates a new parser with a custom `BitStackConfig`.
    ///
    /// This parser assumes no string escapes will be encountered. If escapes are found,
    /// parsing will fail. For JSON with escapes, use `with_config_and_buffer`.
    pub fn with_config(input: &'a str) -> Self {
        Self::with_config_from_slice(input.as_bytes())
    }

    /// Creates a new parser from a byte slice with a custom `BitStackConfig`.
    ///
    /// Assumes no string escapes will be encountered. For JSON with escapes, use [`with_config_and_buffer_from_slice`].
    ///
    /// [`with_config_and_buffer_from_slice`]: Self::with_config_and_buffer_from_slice
    pub fn with_config_from_slice(input: &'a [u8]) -> Self {
        Self::with_config_and_buffer_from_slice(input, &mut [])
    }

    /// Creates a new parser with a custom `BitStackConfig` and a user-provided scratch buffer.
    ///
    /// Use this when your JSON contains string escapes (like `\n`, `\"`, `\u0041`).
    ///
    /// # Arguments
    /// * `input` - A string slice containing the JSON data to be parsed.
    /// * `scratch_buffer` - A mutable byte slice for temporary string unescaping operations.
    ///   This buffer needs to be at least as long as the longest
    ///   contiguous token (string, key, number) in the input.
    pub fn with_config_and_buffer(input: &'a str, scratch_buffer: &'b mut [u8]) -> Self {
        Self::with_config_and_buffer_from_slice(input.as_bytes(), scratch_buffer)
    }

    /// Creates a new parser from a byte slice with a custom `BitStackConfig` and scratch buffer.
    ///
    /// Use when JSON contains string escapes that need unescaping.
    /// This is the core constructor that all other constructors delegate to.
    pub fn with_config_and_buffer_from_slice(
        input: &'a [u8],
        scratch_buffer: &'b mut [u8],
    ) -> Self {
        SliceParser {
            parser_core: ParserCore::new(),
            content_builder: SliceContentBuilder::new(input, scratch_buffer),
        }
    }

    /// Returns the next JSON event or an error if parsing fails.
    /// Parsing continues until `EndDocument` is returned or an error occurs.
    fn next_event_impl(&mut self) -> Result<Event<'_, '_>, ParseError> {
        // Use the unified ParserCore implementation with SliceParser-specific timing
        // No byte accumulation needed for SliceParser (pass no-op closure)
        self.parser_core.next_event_impl(
            &mut self.content_builder,
            EscapeTiming::OnBegin,
            |_, _| Ok(()),
        )
    }
}

impl<C: BitStackConfig> PullParser for SliceParser<'_, '_, C> {
    fn next_event(&mut self) -> Result<Event<'_, '_>, ParseError> {
        if self.content_builder.buffer().is_past_end() {
            return Ok(Event::EndDocument);
        }
        self.next_event_impl()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{ArrayBitStack, BitStackStruct, String};

    #[test]
    fn make_parser() {
        let input = r#"{"key": "value"}"#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);
        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(parser.next_event(), Ok(Event::Key(String::Borrowed("key"))));
        assert_eq!(
            parser.next_event(),
            Ok(Event::String(String::Borrowed("value")))
        );
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn parse_number() {
        let input = r#"{"key": 124}"#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);
        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(parser.next_event(), Ok(Event::Key(String::Borrowed("key"))));
        // Check number value using new JsonNumber API
        match parser.next_event() {
            Ok(Event::Number(num)) => {
                assert_eq!(num.as_str(), "124");
                assert_eq!(num.as_int(), Some(124));
            }
            other => panic!("Expected Number, got: {:?}", other),
        }
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn parse_bool_and_null() {
        let input = r#"{"key": true, "key2": false, "key3": null}"#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);
        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(parser.next_event(), Ok(Event::Key(String::Borrowed("key"))));
        assert_eq!(parser.next_event(), Ok(Event::Bool(true)));
        assert_eq!(
            parser.next_event(),
            Ok(Event::Key(String::Borrowed("key2")))
        );
        assert_eq!(parser.next_event(), Ok(Event::Bool(false)));
        assert_eq!(
            parser.next_event(),
            Ok(Event::Key(String::Borrowed("key3")))
        );
        assert_eq!(parser.next_event(), Ok(Event::Null));
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn parse_array() {
        #[cfg(feature = "float-error")]
        let input = r#"{"key": [1, 2, 3]}"#; // No floats for float-error config
        #[cfg(not(feature = "float-error"))]
        let input = r#"{"key": [1, 2.2, 3]}"#; // Include float for other configs

        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);
        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(parser.next_event(), Ok(Event::Key(String::Borrowed("key"))));
        assert_eq!(parser.next_event(), Ok(Event::StartArray));

        // First number: 1 (integer)
        match parser.next_event() {
            Ok(Event::Number(num)) => {
                assert_eq!(num.as_str(), "1");
                assert_eq!(num.as_int(), Some(1));
            }
            other => panic!("Expected Number(1), got: {:?}", other),
        }

        // Second number: depends on configuration
        match parser.next_event() {
            Ok(Event::Number(num)) => {
                #[cfg(feature = "float-error")]
                {
                    assert_eq!(num.as_str(), "2");
                    assert_eq!(num.as_int(), Some(2));
                }
                #[cfg(not(feature = "float-error"))]
                {
                    assert_eq!(num.as_str(), "2.2");
                    #[cfg(feature = "float")]
                    assert_eq!(num.as_f64(), Some(2.2));
                    #[cfg(not(feature = "float-error"))]
                    assert!(num.is_float());
                }
            }
            other => panic!("Expected Number, got: {:?}", other),
        }

        // Third number: 3 (integer)
        match parser.next_event() {
            Ok(Event::Number(num)) => {
                assert_eq!(num.as_str(), "3");
                assert_eq!(num.as_int(), Some(3));
            }
            other => panic!("Expected Number(3), got: {:?}", other),
        }

        assert_eq!(parser.next_event(), Ok(Event::EndArray));
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_simple_parser_api() {
        let input = r#"{"name": "test"}"#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);

        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(
            parser.next_event(),
            Ok(Event::Key(String::Borrowed("name")))
        );
        assert_eq!(
            parser.next_event(),
            Ok(Event::String(String::Borrowed("test")))
        );
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_parser_with_escaped_strings() {
        // Use regular string literal to properly include escape sequences
        let input = "{\"name\": \"John\\nDoe\", \"message\": \"Hello\\tWorld!\"}";
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);

        // Test that the parser correctly handles escaped strings
        assert_eq!(parser.next_event(), Ok(Event::StartObject));

        // Key should be simple (no escapes) -> Borrowed
        if let Ok(Event::Key(key)) = parser.next_event() {
            assert_eq!(&*key, "name");
            // This should be the fast path (borrowed)
            assert!(matches!(key, String::Borrowed(_)));
        } else {
            panic!("Expected Key event");
        }

        // Value should have escapes -> Unescaped
        if let Ok(Event::String(value)) = parser.next_event() {
            assert_eq!(&*value, "John\nDoe");
            // This should be the slow path (unescaped)
            assert!(matches!(value, String::Unescaped(_)));
        } else {
            panic!("Expected String event");
        }

        // Second key should be simple -> Borrowed
        if let Ok(Event::Key(key)) = parser.next_event() {
            assert_eq!(&*key, "message");
            assert!(matches!(key, String::Borrowed(_)));
        } else {
            panic!("Expected Key event");
        }

        // Second value should have escapes -> Unescaped
        if let Ok(Event::String(value)) = parser.next_event() {
            assert_eq!(&*value, "Hello\tWorld!");
            assert!(matches!(value, String::Unescaped(_)));
        } else {
            panic!("Expected String event");
        }

        assert_eq!(parser.next_event(), Ok(Event::EndObject));
    }

    #[test]
    fn test_copy_on_escape_optimization() {
        // Use regular string literal to include proper escape sequences
        let input = "{\"simple\": \"no escapes\", \"complex\": \"has\\nescapes\"}";
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);

        assert_eq!(parser.next_event(), Ok(Event::StartObject));

        // "simple" key should be borrowed (fast path)
        if let Ok(Event::Key(key)) = parser.next_event() {
            assert_eq!(&*key, "simple");
            assert!(matches!(key, String::Borrowed(_)));
        } else {
            panic!("Expected Key event");
        }

        // "no escapes" value should be borrowed (fast path)
        if let Ok(Event::String(value)) = parser.next_event() {
            assert_eq!(&*value, "no escapes");
            assert!(matches!(value, String::Borrowed(_)));
        } else {
            panic!("Expected String event");
        }

        // "complex" key should be borrowed (fast path)
        if let Ok(Event::Key(key)) = parser.next_event() {
            assert_eq!(&*key, "complex");
            assert!(matches!(key, String::Borrowed(_)));
        } else {
            panic!("Expected Key event");
        }

        // "has\\nescapes" value should be unescaped (slow path)
        if let Ok(Event::String(value)) = parser.next_event() {
            assert_eq!(&*value, "has\nescapes");
            assert!(matches!(value, String::Unescaped(_)));
        } else {
            panic!("Expected String event");
        }

        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_coe2_integration_multiple_escapes() {
        let input = r#"{"key": "a\nb\tc\rd"}"#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);

        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(parser.next_event(), Ok(Event::Key(String::Borrowed("key"))));

        let string_event = parser.next_event().unwrap();
        match string_event {
            Event::String(String::Unescaped(s)) => {
                assert_eq!(s, "a\nb\tc\rd");
            }
            _ => panic!("Expected unescaped string value, got: {:?}", string_event),
        }
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_coe2_integration_zero_copy_path() {
        let input = r#"{"simple": "no_escapes_here"}"#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);

        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(
            parser.next_event(),
            Ok(Event::Key(String::Borrowed("simple")))
        );

        // This should be borrowed (zero-copy) since no escapes
        let string_event = parser.next_event().unwrap();
        match string_event {
            Event::String(String::Borrowed(s)) => {
                assert_eq!(s, "no_escapes_here");
            }
            _ => panic!(
                "Expected borrowed string value for zero-copy, got: {:?}",
                string_event
            ),
        }
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_coe2_integration_mixed_strings() {
        let input = r#"["plain", "with\nescapes", "plain2", "more\tescapes"]"#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);

        assert_eq!(parser.next_event(), Ok(Event::StartArray));

        // First string: no escapes -> borrowed
        match parser.next_event().unwrap() {
            Event::String(String::Borrowed(s)) => assert_eq!(s, "plain"),
            other => panic!("Expected borrowed string, got: {:?}", other),
        }

        // Second string: has escapes -> unescaped
        match parser.next_event().unwrap() {
            Event::String(String::Unescaped(s)) => assert_eq!(s, "with\nescapes"),
            other => panic!("Expected unescaped string, got: {:?}", other),
        }

        // Third string: no escapes -> borrowed
        match parser.next_event().unwrap() {
            Event::String(String::Borrowed(s)) => assert_eq!(s, "plain2"),
            other => panic!("Expected borrowed string, got: {:?}", other),
        }

        // Fourth string: has escapes -> unescaped
        match parser.next_event().unwrap() {
            Event::String(String::Unescaped(s)) => assert_eq!(s, "more\tescapes"),
            other => panic!("Expected unescaped string, got: {:?}", other),
        }

        assert_eq!(parser.next_event(), Ok(Event::EndArray));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_unicode_escape_integration() {
        let input = r#"{"key": "Hello\u0041World"}"#; // \u0041 = 'A'
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);

        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(parser.next_event(), Ok(Event::Key(String::Borrowed("key"))));

        // The string with Unicode escape should be unescaped
        match parser.next_event().unwrap() {
            Event::String(String::Unescaped(s)) => {
                assert_eq!(s, "HelloAWorld");
            }
            other => panic!("Expected unescaped string value, got: {:?}", other),
        }

        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_original_parser_escape_trace() {
        // Test escape sequence processing with logging
        let input = r#""a\nb""#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer(input, &mut scratch);

        // Should get String with unescaped content
        let event = parser.next_event().unwrap();
        if let Event::String(s) = event {
            assert_eq!(&*s, "a\nb");
        } else {
            panic!("Expected String event, got {:?}", event);
        }

        // Should get EndDocument
        let event = parser.next_event().unwrap();
        assert_eq!(event, Event::EndDocument);
    }

    #[test]
    fn make_parser_from_slice() {
        let input = br#"{"key": "value"}"#;
        let mut scratch = [0u8; 1024];
        let mut parser = SliceParser::with_buffer_from_slice(input, &mut scratch);
        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(parser.next_event(), Ok(Event::Key(String::Borrowed("key"))));
        assert_eq!(
            parser.next_event(),
            Ok(Event::String(String::Borrowed("value")))
        );
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_with_config_constructors() {
        // Test with_config constructor (no escapes)
        let json = r#"{"simple": "no_escapes"}"#;
        let mut parser = SliceParser::<BitStackStruct<u64, u16>>::with_config(json);

        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(
            parser.next_event(),
            Ok(Event::Key(String::Borrowed("simple")))
        );
        assert_eq!(
            parser.next_event(),
            Ok(Event::String(String::Borrowed("no_escapes")))
        );
        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_with_config_and_buffer_constructors() {
        // Test with_config_and_buffer constructor (with escapes)
        let json = r#"{"escaped": "hello\nworld"}"#;
        let mut scratch = [0u8; 64];
        let mut parser =
            SliceParser::<BitStackStruct<u64, u16>>::with_config_and_buffer(json, &mut scratch);

        assert_eq!(parser.next_event(), Ok(Event::StartObject));
        assert_eq!(
            parser.next_event(),
            Ok(Event::Key(String::Borrowed("escaped")))
        );

        if let Ok(Event::String(s)) = parser.next_event() {
            assert_eq!(s.as_ref(), "hello\nworld"); // Escape should be processed
        } else {
            panic!("Expected String event");
        }

        assert_eq!(parser.next_event(), Ok(Event::EndObject));
        assert_eq!(parser.next_event(), Ok(Event::EndDocument));
    }

    #[test]
    fn test_alternative_config_deep_nesting() {
        // Test that custom BitStack configs can handle deeper nesting
        let json = r#"{"a":{"b":{"c":{"d":{"e":"deep"}}}}}"#;
        let mut scratch = [0u8; 64];
        let mut parser =
            SliceParser::<ArrayBitStack<8, u32, u16>>::with_config_and_buffer(json, &mut scratch);

        // Parse the deep structure
        let mut depth = 0;
        while let Ok(event) = parser.next_event() {
            match event {
                Event::StartObject => depth += 1,
                Event::EndObject => depth -= 1,
                Event::EndDocument => break,
                _ => {}
            }
        }

        // Should have successfully parsed a 5-level deep structure
        assert_eq!(depth, 0); // All objects should be closed
    }
}