mathcat_c 0.7.0

//! When calling from C, the general ordering is:
//! 1. whatever preferences the AT needs to set, it is done with calls to [`SetPreference`].
//! 2. the MathML is sent over via [`SetMathML`].
//! 3. AT calls to get the speech [`GetSpokenText`] and calls [`GetBraille`] to get the (Unicode) braille.
//! 
//! It is also possible to find out the current value of a preference by calling [`GetPreference`]
//! 
//! Navigation can be done via calls to either:
//! * [`DoNavigateKeyPress`] (takes key events as input)
//! * [`DoNavigateCommand`] (takes the commands the key events internally map to)
//! Both return a string to speak.
//! To highlight the node on is on, 'id's are used. If they weren't already present,
//! [`SetMathML`] returns a string representing MathML that contains 'id's for any node that doesn't already
//! have an 'id' set.
//!
//! You can get the current node with:
//! [GetNavigationLocation] which returns a [NavigationLocation] structure containing the `id` and the `offset`.
//! The node can be set with [SetNavigationLocation].
//! 
//! The MathML associated with the current navigation Location (the entire node, not the part referenced by an `offset`) can be retrieved with:
//! * [`GetNavigationMathML`] -- returns a string representing the MathML for the selected node
//!
//! The braille routing cursor can be used to set the navigation node associated with the braille displayed at that location (0-base) by calling:
//! [GetNavigationLocationFromBraillePosition].
//! Like [GetNavigationLocation] which returns a [NavigationLocation] structure containing the `id` and the `offset`.
//!
//! AT can pass key strokes to allow a user to navigate the MathML by calling [`DoNavigateKeyPress`]; the speech is returned.
//! To get the MathML associated with the current navigation node, call [`GetNavigationMathML`].
//!
//! Internally, Rust returns a Result<> type. I don't know how to express this in the interface (maybe it is possible via enums?).
//! Instead, most functions return a string. When the string is empty, that indicates an error.
//! For functions that one doesn't normally expect a string (e.g, [`SetRulesDir`]), "Ok" is returned for consistency.
//! For errors, call [`GetError`]: it returns a string representing the error.
//! 
//! IMPORTANT: Rust allocates all the strings and its allocator and C's allocator and not compatible.
//!   EVERY string returned from Rust (including errors/empty strings) must be deallocated by calling FreeMathCATString().
//! Failure to call FreeMathCATString() will result in a memory leak.

#![allow(non_snake_case)]
#![allow(clippy::needless_return)]

use libmathcat::*;
use std::cell::RefCell;
use std::ffi::{CString, CStr};
use std::os::raw::c_char;

const ILLEGAL_STRING: &str = "Internal MathCAT error -- internal null";
// const ILLEGAL_CStr: &str = "Illegal bytes in UTF8 input string";
thread_local!{
    /// The current node being navigated (also spoken and brailled) is stored in `MATHML_INSTANCE`.
    pub static ERROR_STRING: RefCell<String> = RefCell::new(String::default());
}

fn change_error_string_value(new_string: String) {
    ERROR_STRING.with(|string: &RefCell<String>| {
        let mut string = string.borrow_mut();
        string.clear();
        string.push_str(&new_string);
    })
}

#[no_mangle]
/// Returns the error set by the last call.
/// Calling GetError() will clear the current error.
/// If there is no error, "" (an empty string) will be returned.
pub extern "C" fn GetError() -> *const c_char {
    ERROR_STRING.with(|string: &RefCell<String>| {
        let mut string = string.borrow_mut();
        let result = CString::new(string.as_bytes()).expect(ILLEGAL_STRING);
        string.clear();
        return result.into_raw();
    })
}



fn safe_string(cstr: *const c_char) -> String {
    return unsafe {
        CStr::from_ptr(cstr).to_string_lossy().into_owned()
    }
}

/// The error type returned from MathCAT is from an error package, so we can't implement From on it.
/// Instead, we write a wrapper function that deals with the error conversion
fn set_string_error(result: Result<String, libmathcat::errors::Error>) -> *const c_char {
    let result =  match result {
        Ok(answer) => CString::new(answer).expect(ILLEGAL_STRING),
        Err(e) => {
            change_error_string_value(errors_to_string(&e));
            CString::new("").unwrap()
        },
    };
    return result.into_raw();
}

fn set_int_error(result: Result<usize, libmathcat::errors::Error>) -> u32 {
    return match result {
        Ok(answer) => answer as u32,
        Err(e) => {
            change_error_string_value(errors_to_string(&e));
            0
        },
    };
}

fn set_empty_error(result: Result<(), libmathcat::errors::Error>) -> *const c_char {
    let result = match result {
        Ok(_) => CString::new("Ok").expect(ILLEGAL_STRING),
        Err(e) => {
            change_error_string_value(errors_to_string(&e));
            CString::new("").unwrap()
        },
    };
    return result.into_raw();
}

#[no_mangle]
/// IMPORTANT: For every MathCAT function that returns a string, it must be free'd with this call
/// If this is not called, the memory will be leaked.
pub extern "C" fn FreeMathCATString(str: *mut c_char) {
    unsafe{
        if !str.is_null() {
            drop(CString::from_raw(str));
        };
    }
}

#[no_mangle]
/// The absolute path location of the MathCAT Rules dir.
/// Returns "Ok" or an empty string if there is an error (use GetError()).
/// IMPORTANT: This should be the first call to MathCAT
pub extern "C" fn SetRulesDir(rules_dir_location: *const c_char) -> *const c_char {
    return set_empty_error(
        set_rules_dir(safe_string(rules_dir_location))
    );
}

#[no_mangle]
/// The MathML to be spoken, brailled, or navigated.
///
/// This will override any previous MathML that was set.
/// Returns: the MathML that was set, annotated with 'id' values on each node (if none were present)
/// The 'id' values can be used during navigation for highlighting the current node
pub extern "C" fn SetMathML(mathml_str: *const c_char) -> *const c_char {
    return set_string_error(
        set_mathml(safe_string(mathml_str))
    );
}

#[no_mangle]
/// Get the spoken text of the MathML that was set.
/// The speech takes into account any AT or user preferences.
pub extern "C" fn GetMathCATVersion() -> *const c_char {    
    return set_string_error( Ok(get_version()) );
}

#[no_mangle]
/// Get the spoken text of the MathML that was set.
/// The speech takes into account any AT or user preferences.
pub extern "C" fn GetSpokenText() -> *const c_char {
    return set_string_error( get_spoken_text() );
}

#[no_mangle]
/// Set an API preference. The preference name should be a known preference name.
/// The value should either be a string or a number (depending upon the preference being set)
///
/// This function can be called multiple times to set different values.
/// The values are persistent but can be overwritten by setting a preference with the same name and a different value.
pub extern "C" fn SetPreference(name: *const c_char, value: *const c_char) -> *const c_char {
    let name = safe_string(name);
    let value = safe_string(value);
    return set_empty_error( set_preference(name, value) );
}

#[no_mangle]
/// Set an API preference. The preference name should be a known preference name.
/// The value should either be a string or a number (depending upon the preference being set)
///
/// This function can be called multiple times to set different values.
/// The values are persistent but can be overwritten by setting a preference with the same name and a different value.
pub extern "C" fn GetPreference(name: *const c_char) -> *const c_char {
    return match get_preference( safe_string(name) ) {
        Ok(value) => {
            set_string_error( Ok(value))
        },
        Err(_) => {
            change_error_string_value( format!("Unknown preference name {}", safe_string(name)) );
            set_string_error( Ok( String::default() ) )
        },
    };
}

#[no_mangle]
/// Get the braille associated with the MathML that was set by [`set_mathml`].
/// The braille returned depends upon the preference for the `code` preference (default `Nemeth`).
/// 
/// If 'nav_node_id' is a non-empty string, the node is highlighted based on the value of `BrailleNavHighlight` (default: `EndPoints`)
pub extern "C" fn GetBraille(nav_node_id: *const c_char) -> *const c_char {
    return set_string_error( get_braille(safe_string(nav_node_id)) );
}

#[no_mangle]
/// Get the braille associated with the current navigation focus of the MathML that was set by [`set_mathml`].
/// The braille returned depends upon the preference for the `code` preference (default `Nemeth`).
/// 
/// The returned braille is brailled as if the current navigation focus is the entire expression to be brailled.
pub extern "C" fn GetNavigationBraille() -> *const c_char {
    return set_string_error( get_navigation_braille() );
}

#[no_mangle]
/// Given a key code along with the modifier keys, the current node is moved accordingly (or value reported in some cases).
///
/// The spoken text for the new current node is returned.
pub extern "C" fn DoNavigateKeyPress(key: usize, shift_key: bool, control_key: bool, alt_key: bool, meta_key: bool) -> *const c_char {
    return set_string_error( do_navigate_keypress(key, shift_key, control_key, alt_key, meta_key) );
}

#[no_mangle]
/// Given a command, the current node is moved accordingly (or value reported in some cases).
///
/// The spoken text for the new current node is returned.
/// 
/// The list of legal commands are:
/// "MovePrevious", "MoveNext", "MoveStart", "MoveEnd", "MoveLineStart", "MoveLineEnd", 
/// "MoveCellPrevious", "MoveCellNext", "MoveCellUp", "MoveCellDown", "MoveColumnStart", "MoveColumnEnd", 
/// "ZoomIn", "ZoomOut", "ZoomOutAll", "ZoomInAll", 
/// "MoveLastLocation", 
/// "ReadPrevious", "ReadNext", "ReadCurrent", "ReadCellCurrent", "ReadStart", "ReadEnd", "ReadLineStart", "ReadLineEnd", 
/// "DescribePrevious", "DescribeNext", "DescribeCurrent", 
/// "WhereAmI", "WhereAmIAll", 
/// "ToggleZoomLockUp", "ToggleZoomLockDown", "ToggleSpeakMode", 
/// "Exit", 
/// "MoveTo0","MoveTo1","MoveTo2","MoveTo3","MoveTo4","MoveTo5","MoveTo6","MoveTo7","MoveTo8","MoveTo9",
/// "Read0","Read1","Read2","Read3","Read4","Read5","Read6","Read7","Read8","Read9",
/// "Describe0","Describe1","Describe2","Describe3","Describe4","Describe5","Describe6","Describe7","Describe8","Describe9",
/// "SetPlacemarker0","SetPlacemarker1","SetPlacemarker2","SetPlacemarker3","SetPlacemarker4","SetPlacemarker5","SetPlacemarker6","SetPlacemarker7","SetPlacemarker8","SetPlacemarker9",
pub extern "C" fn DoNavigateCommand(command: *const c_char) -> *const c_char {
    return set_string_error( do_navigate_command(safe_string(command)) );
}

#[no_mangle]
/// Return the MathML associated with the current (navigation) node.
pub extern "C" fn GetNavigationMathML() -> *const c_char {
    return match get_navigation_mathml() {
        Err(e) => set_string_error(Err(e)),
        Ok((nav_mathml, _)) => set_string_error( Ok(nav_mathml) ),
    }
}


#[no_mangle]
/// Return the id of the MathML associated with the current (navigation) node.
/// Note: this is deprecated -- use GetNavigationLocation()
pub extern "C" fn GetNavigationMathMLId() -> *const c_char {
    return match get_navigation_mathml_id() {
        Err(e) => set_string_error(Err(e)),
        Ok((nav_id, _)) => set_string_error( Ok(nav_id) ),
    }
}
/// Return the id of the MathML associated with the current (navigation) node.
/// Note: this is deprecated -- use GetNavigationLocation()
pub extern "C" fn GetNavigationMathMLIdOffset() -> u32 {
    return match get_navigation_mathml_id() {
        Err(e) => set_int_error(Err(e)),
        Ok((_, nav_offset)) => set_int_error( Ok(nav_offset) ),
    }
}

#[no_mangle]
/// Return the offset from the MathML node associated with the current (navigation) node.
/// Note: this is deprecated -- use GetNavigationLocation()
pub extern "C" fn GetNavigationMathMLOffset() -> u32 {
    return match get_navigation_mathml() {
        Err(e) => set_int_error(Err(e)),
        Ok((_, nav_offset)) => set_int_error( Ok(nav_offset) ),
    }
}

#[repr(C)]
/// `NavigationLocation` is a structure used with Navigation.
/// In many cases, the `id` is enough to uniquely identify the navigation location.
/// However, for a number such as "123" or an identifier such as "sin", there is no `id` representing each character.
/// An `offset` is used to uniquely identify each character. `offset` = 0 is the entire identifier, 1 is the first char, etc.
/// For example, the "i" in `<mi id='xyz-123'>sin</mi>` has `id="xyz-123"` and `offset=1`.
///
/// Note: currently (2/24) offsets are not implemented in MathCAT and will always return 0. This will hopefully be supported by the end of 2024.
pub struct NavigationLocation {
    id: *const c_char,
    offset: u32,
}

#[no_mangle]
/// Set the location of the navigation node associated with the current MathML expression.
/// Returns "Ok" or an empty string if there is an error (use GetError()).
pub extern "C" fn SetNavigationLocation(location: NavigationLocation) -> *const c_char {
    return set_empty_error(
        set_navigation_node(safe_string(location.id), location.offset as usize)
    )
}

#[no_mangle]
/// Return the NavigationLocation (id and offset) associated with the current (navigation) node.
/// If there is an error, the id is set to an empty string (use GetError()).
pub extern "C" fn GetNavigationLocation() -> NavigationLocation {
    return match get_navigation_mathml_id() {
        Err(e) => {
            change_error_string_value(errors_to_string(&e));
            NavigationLocation {
                id: CString::new("").unwrap().into_raw(),
                offset: 0_u32,
            }
        },
        Ok((nav_id, nav_offset)) => {
            NavigationLocation {
                id: CString::new(nav_id).expect(ILLEGAL_STRING).into_raw(),
                offset: nav_offset as u32,
            }
        },
    }
}

#[no_mangle]
/// Return the NavigationLocation (id and offset) associated with braille cursor location (0-based).
/// If there is an error, the id is set to an empty string (use GetError()).
pub extern "C" fn GetNavigationLocationFromBraillePosition(position: u32) -> NavigationLocation {
    return match get_navigation_node_from_braille_position(position as usize) {
        Err(e) => {
            change_error_string_value(errors_to_string(&e));
            NavigationLocation {
                id: CString::new("").unwrap().into_raw(),
                offset: 0_u32,
            }
        },
        Ok((nav_id, nav_offset)) => {
            NavigationLocation {
                id: CString::new(nav_id).expect(ILLEGAL_STRING).into_raw(),
                offset: nav_offset as u32,
            }
        },
    }
}

#[repr(C)]
pub struct CStringArray {
    pub data: *mut *mut c_char,
    pub len: usize,
}

#[no_mangle]
/// Call this when you are done with the CStringArray returned by a function.
pub extern "C" fn FreeMathCATStringArray(array: CStringArray) {
    unsafe {
        let mut vec = Vec::from_raw_parts(array.data, array.len, array.len); // Reconstruct Vec
        for ptr in vec.drain(..) {
            let _ = CString::from_raw(ptr); // Reconstruct CString to drop it
        }
    }
}

#[no_mangle]
/// Return the braille codes that are supported in this version of MathCAT.
/// If there is an error, the id is set to an empty string (use GetError()).
pub extern "C" fn GetSupportedBrailleCodes() -> CStringArray {
    return vec_to_cstring_array(libmathcat::get_supported_braille_codes());
}

#[no_mangle]
/// Return the braille codes that are supported in this version of MathCAT.
/// If there is an error, the id is set to an empty string (use GetError()).
pub extern "C" fn GetSupportedLanguages() -> CStringArray {
    return vec_to_cstring_array(libmathcat::get_supported_languages());
}

#[no_mangle]
/// Return the braille codes that are supported in this version of MathCAT.
/// If there is an error, the id is set to an empty string (use GetError()).
pub extern "C" fn GetSupportedSpeechStyles(language: *const c_char) -> CStringArray {
    return vec_to_cstring_array(libmathcat::get_supported_speech_styles(safe_string(language)));
}

fn vec_to_cstring_array(vec: Vec<String>) -> CStringArray {
    let mut c_strings: Vec<*mut c_char> = vec.iter()
        .map(|s| CString::new(s.as_bytes()).expect(ILLEGAL_STRING).into_raw())
        .collect();
    let len = c_strings.len();
    let data = c_strings.as_mut_ptr();
    std::mem::forget(c_strings); // prevent Rust from freeing the memory
    return CStringArray { data, len };
}