leach 0.3.0

// Copyright (c) 2022-2026 Sprite Tong (<spritetong@gmail.com>)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

//! Build configuration and FFI binding generation for C/C++ projects.
//! Provides `BindgenConfig` for header parsing and code generation via `bindgen`.

use super::*;
use std::{
    borrow::Cow,
    collections::{hash_map::DefaultHasher, BTreeMap, VecDeque},
    hash::{Hash, Hasher},
    io::Read,
};

/// Configuration builder for generating Rust FFI bindings from C/C++ headers.
#[derive(Clone, Default, Hash)]
pub struct Bindgen {
    rs_file: Option<PathBuf>,
    allow_bad_code_styles: bool,
    headers: Vec<String>,
    includes: Vec<String>,
    definitions: Vec<(String, String)>,
    allowlist: Vec<String>,
    blocklist: Vec<String>,
    header_codes: Vec<String>,
    footer_codes: Vec<String>,
    derive: BTreeMap<String, Vec<String>>,
}

/// Callback invoked before bindgen code generation.
///
/// Receives a mutable reference to the `Bindgen` config and the
/// `bindgen::Builder`, allowing last-minute modifications to headers,
/// flags, or builder settings before code generation runs.
pub type BeforeBindgenCb =
    dyn FnOnce(&mut Bindgen, bindgen::Builder) -> io::Result<bindgen::Builder>;

impl Bindgen {
    /// Sets the output Rust file path for the generated bindings.
    ///
    /// # Arguments
    /// * `rs_file` - Path to the output Rust file
    pub fn rs_file<T: Into<PathBuf>>(&mut self, rs_file: T) -> &mut Self {
        self.rs_file = Some(rs_file.into());
        self
    }

    /// Enables generation of code that may not follow Rust style guidelines.
    pub fn allow_bad_code_styles(&mut self) -> &mut Self {
        self.allow_bad_code_styles = true;
        self
    }

    /// Enforces Rust style guidelines in generated code.
    pub fn deny_bad_code_styles(&mut self) -> &mut Self {
        self.allow_bad_code_styles = false;
        self
    }

    /// Adds a header file to be processed for FFI binding generation.
    ///
    /// # Arguments
    /// * `header` - Path to the C/C++ header file
    pub fn header<T: AsRef<Path>>(&mut self, header: T) -> &mut Self {
        self.headers.push(Self::norm_path(realpath(header)));
        self
    }

    /// Adds multiple header files to be processed for FFI binding generation.
    ///
    /// # Arguments
    /// * `headers` - Iterator of paths to C/C++ header files
    pub fn headers<T>(&mut self, headers: T) -> &mut Self
    where
        T: IntoIterator,
        T::Item: AsRef<Path>,
    {
        self.headers
            .extend(headers.into_iter().map(|x| Self::norm_path(realpath(x))));
        self
    }

    /// Adds an include directory for header file resolution.
    ///
    /// # Arguments
    /// * `include` - Path to include directory
    pub fn include<T: AsRef<Path>>(&mut self, include: T) -> &mut Self {
        self.includes.push(Self::norm_path(include));
        self
    }

    /// Adds multiple include directories for header file resolution.
    ///
    /// # Arguments
    /// * `includes` - Iterator of paths to include directories
    pub fn includes<T>(&mut self, includes: T) -> &mut Self
    where
        T: IntoIterator,
        T::Item: AsRef<Path>,
    {
        self.includes
            .extend(includes.into_iter().map(Self::norm_path));
        self
    }

    /// Sets the include directories from cmkabe's configuration.
    pub fn cmake_includes(&mut self) -> &mut Self {
        for dir in cmkabe::cmake_include_dirs() {
            self.includes.push(dir.display().to_string());
        }
        self
    }

    /// Adds a preprocessor definition.
    ///
    /// # Arguments
    /// * `name` - Name of the macro to define
    /// * `value` - Value to define the macro as
    pub fn definition<K, V>(&mut self, name: K, value: V) -> &mut Self
    where
        K: Into<String>,
        V: Into<String>,
    {
        self.definitions.push((name.into(), value.into()));
        self
    }

    /// Adds multiple preprocessor definitions.
    ///
    /// # Arguments
    /// * `definitions` - Iterator of (name, value) pairs for macro definitions
    pub fn definitions<T, K, V>(&mut self, definitions: T) -> &mut Self
    where
        T: IntoIterator<Item = (K, V)>,
        K: Into<String>,
        V: Into<String>,
    {
        self.definitions
            .extend(definitions.into_iter().map(|(k, v)| (k.into(), v.into())));
        self
    }

    /// Specifies items to include in the bindings (whitelist).
    ///
    /// # Arguments
    /// * `allowlist` - Iterator of item names to include
    pub fn allowlist<T>(&mut self, allowlist: T) -> &mut Self
    where
        T: IntoIterator,
        T::Item: Into<String>,
    {
        self.allowlist
            .extend(allowlist.into_iter().map(|x| x.into()));
        self
    }

    /// Specifies items to exclude from the bindings (blacklist).
    ///
    /// # Arguments
    /// * `blocklist` - Iterator of item names to exclude
    pub fn blocklist<T>(&mut self, blocklist: T) -> &mut Self
    where
        T: IntoIterator,
        T::Item: Into<String>,
    {
        self.blocklist
            .extend(blocklist.into_iter().map(|x| x.into()));
        self
    }

    /// Adds a raw line of Rust code at the beginning of the generated bindings.
    ///
    /// # Arguments
    /// * `line` - Line of Rust code to add
    pub fn raw_line<T: Into<String>>(&mut self, line: T) -> &mut Self {
        self.header_codes.push(line.into());
        self
    }

    /// Adds multiple raw lines of Rust code at the beginning of the generated bindings.
    ///
    /// # Arguments
    /// * `lines` - Iterator of Rust code lines to add
    pub fn raw_lines<T>(&mut self, lines: T) -> &mut Self
    where
        T: IntoIterator,
        T::Item: Into<String>,
    {
        self.header_codes
            .extend(lines.into_iter().map(|x| x.into()));
        self
    }

    /// Adds a raw line of Rust code at the end of the generated bindings.
    ///
    /// # Arguments
    /// * `line` - Line of Rust code to add
    pub fn tail_raw_line<T: Into<String>>(&mut self, line: T) -> &mut Self {
        self.footer_codes.push(line.into());
        self
    }

    /// Adds multiple raw lines of Rust code at the end of the generated bindings.
    ///
    /// # Arguments
    /// * `lines` - Iterator of Rust code lines to add
    pub fn tail_raw_lines<T>(&mut self, lines: T) -> &mut Self
    where
        T: IntoIterator,
        T::Item: Into<String>,
    {
        self.footer_codes
            .extend(lines.into_iter().map(|x| x.into()));
        self
    }

    /// Specifies trait derivations for generated types.
    ///
    /// # Arguments
    /// * `types` - Types to apply the derivations to
    /// * `traits` - Traits to derive
    pub fn derive<N, T>(&mut self, types: T, traits: N) -> &mut Self
    where
        T: IntoIterator,
        T::Item: Into<String>,
        N: IntoIterator,
        N::Item: Into<String>,
    {
        let mut types = types.into_iter().map(|x| x.into()).collect::<Vec<String>>();
        let traits = traits
            .into_iter()
            .map(|x| x.into())
            .collect::<Vec<String>>();
        if types.is_empty() {
            types.push(String::new())
        }
        for ty in types.iter() {
            if !self.derive.contains_key(ty) {
                self.derive.insert(ty.clone(), Vec::new());
            }
            let lst = self.derive.get_mut(ty).unwrap();
            for tr in traits.iter() {
                if !lst.contains(tr) {
                    lst.push(tr.clone());
                }
            }
        }
        self
    }

    /// Generates the Rust FFI bindings based on the configured settings.
    ///
    /// # Arguments
    /// * `f` - Optional callback for additional builder configuration
    ///
    /// # Returns
    /// * `io::Result<()>` - Success or error status
    pub fn generate(&mut self, f: Option<Box<BeforeBindgenCb>>) -> io::Result<()> {
        use bindgen::callbacks::ParseCallbacks;
        #[derive(Debug)]
        struct DependCallbacks {
            root: String,
            cell: RefCell<(fs::File, HashSet<String>)>,
        }
        impl ParseCallbacks for DependCallbacks {
            fn include_file(&self, filename: &str) {
                let filename = Bindgen::norm_path(filename);
                if filename.starts_with(&self.root) {
                    let mut cell = self.cell.borrow_mut();
                    if !cell.1.contains(&filename) {
                        let _ = writeln!(cell.0, "{}", &filename);
                        rerun_if_changed(&filename);
                        cell.1.insert(filename);
                    }
                }
            }
        }
        impl DependCallbacks {
            fn new(root: &Path, dep_file: &Path, headers: &[String]) -> io::Result<Self> {
                let cb = Self {
                    root: Bindgen::norm_path(root),
                    cell: RefCell::new((
                        fs::OpenOptions::new()
                            .write(true)
                            .truncate(true)
                            .create(true)
                            .open(dep_file)?,
                        HashSet::new(),
                    )),
                };

                for header in headers.iter() {
                    cb.include_file(header);
                }
                // Write an empty line to seperate the original headers from parsed dependencies.
                writeln!(cb.cell.borrow_mut().0)?;

                Ok(cb)
            }

            fn is_rebuild_required(rs_file: &Path, dep_file: &Path, headers: &[String]) -> bool {
                if let Ok(metadata) = fs::metadata(rs_file) {
                    let rs_mtime = FileTime::from_last_modification_time(&metadata);
                    if let Ok(f) = fs::File::open(dep_file) {
                        #[allow(clippy::lines_filter_map_ok)]
                        let lines: Vec<String> = io::BufReader::new(f)
                            .lines()
                            .map_while(Result::ok)
                            .collect();

                        // Compare the current headers to the previous headers.
                        let old: Vec<&String> =
                            lines.iter().take_while(|&x| !x.is_empty()).collect();
                        let matching = headers
                            .iter()
                            .zip(old.iter())
                            .filter(|&(a, &b)| a == b)
                            .count();
                        if matching == headers.len() && matching == old.len() {
                            let mut skip = true;
                            for dep in lines.iter().filter(|&x| !x.is_empty()) {
                                match fs::metadata(dep)
                                    .map(|x| FileTime::from_last_modification_time(&x))
                                {
                                    Ok(mtime) => {
                                        // Check <rs_file> and header file's update timestamp.
                                        if rs_mtime < mtime {
                                            skip = false;
                                            break;
                                        }
                                    }
                                    Err(_) => {
                                        skip = false;
                                        break;
                                    }
                                }
                            }
                            if skip {
                                for dep in lines.iter().filter(|&x| !x.is_empty()) {
                                    rerun_if_changed(dep);
                                }
                                return false;
                            }
                        }
                    }
                }
                true
            }
        }

        let root = Self::norm_path(cargo::workspace_dir());
        let rs_file = match self.rs_file.as_ref() {
            Some(x) => Self::norm_path(realpath(x)),
            _ => return Err(io::Error::new(io::ErrorKind::InvalidData, "No <rs_file>")),
        };

        // Sort headers & derive crates.
        self.headers.sort();

        // File to store dependencies.
        let dep_file = out_dir()
            .with_file_name(
                rs_file
                    .strip_prefix(&root)
                    .and_then(|x| x.strip_prefix('/'))
                    .unwrap_or(&rs_file)
                    .replace(':', "_")
                    .replace('/', "__"),
            )
            .with_extension("leach.d");
        let hash_file = dep_file.with_extension("hash");

        // Watch the output file.
        rerun_if_changed(&rs_file);

        // Check timestamp of dependencies.
        let hash = {
            let mut hasher = DefaultHasher::new();
            self.hash(&mut hasher);
            hasher.finish()
        };
        if !self.is_hash_changed(&hash_file, hash)
            && !DependCallbacks::is_rebuild_required(
                Path::new(&rs_file),
                dep_file.as_ref(),
                self.headers.as_slice(),
            )
        {
            return Ok(());
        }
        // Create file to store dependencies.
        let depen_callback = Box::new(DependCallbacks::new(
            Path::new(&root),
            &dep_file,
            self.headers.as_slice(),
        )?);

        // Create builder.
        let mut builder = Self::default_builder();

        // Common derivation.
        if let Some(traits) = self.derive.get("") {
            for tr in traits {
                match tr.as_str() {
                    "Copy" => builder = builder.derive_copy(true),
                    "Debug" => builder = builder.derive_debug(true),
                    "Default" => builder = builder.derive_default(true),
                    "Hash" => builder = builder.derive_hash(true),
                    "PartialOrd" => builder = builder.derive_partialord(true),
                    "Ord" => builder = builder.derive_ord(true),
                    "PartialEq" => builder = builder.derive_partialeq(true),
                    "Eq" => builder = builder.derive_eq(true),
                    _ => (),
                }
            }
        }

        // C headers
        for header in self.headers.iter() {
            builder = builder.header(header);
        }

        // Include directories
        for include in self.includes.iter() {
            builder = builder.clang_arg(format!("-I{include}"))
        }

        // Macro definitions
        for (name, value) in self.definitions.iter() {
            builder = builder.clang_arg(format!("-D{name}={value}"))
        }

        // Header codes
        if self.allow_bad_code_styles {
            builder = builder
                .raw_line("#![allow(dead_code)]")
                .raw_line("#![allow(improper_ctypes)]")
                .raw_line("#![allow(improper_ctypes_definitions)]")
                .raw_line("#![allow(non_camel_case_types)]")
                .raw_line("#![allow(non_snake_case)]")
                .raw_line("#![allow(non_upper_case_globals)]")
                .raw_line("#![allow(clippy::missing_safety_doc)]")
                .raw_line("#![allow(clippy::missing_transmute_annotations)]")
                .raw_line("#![allow(clippy::too_many_arguments)]")
                .raw_line("#![allow(clippy::useless_transmute)]");
            if !self.header_codes.is_empty() {
                builder = builder.raw_line("");
            }
        }
        for line in self.header_codes.iter() {
            builder = builder.raw_line(line);
        }

        // Set allowlist
        for name in self.allowlist.iter() {
            builder = builder
                .allowlist_function(name)
                .allowlist_type(name)
                .allowlist_var(name);
        }

        // Set blocklist
        for name in self.blocklist.iter() {
            builder = builder.blocklist_item(name);
        }

        // Store depenencies.
        builder = builder.parse_callbacks(depen_callback);

        // Apply custom operation on the builder.
        if let Some(f) = f {
            builder = f(self, builder)?;
        }

        // Build the FFI file.
        let bindings = builder.generate().map_err(io::Error::other)?;

        // Write the .rs file.
        let mut buf = Vec::<u8>::new();
        let mut w = io::Cursor::new(&mut buf);
        bindings.write(Box::new(&mut w))?;
        if !self.footer_codes.is_empty() {
            w.write_all(b"\n")?;
            for line in self.footer_codes.iter() {
                w.write_all(line.as_bytes())?;
                w.write_all(b"\n")?;
            }
        }
        w.flush()?;
        let file = fs::OpenOptions::new()
            .truncate(true)
            .create(true)
            .write(true)
            .open(&rs_file)?;
        Self::apply_derive(self, file, buf)?;

        self.write_hash(&hash_file, hash)
    }

    fn is_hash_changed(&self, hash_file: &Path, hash: u64) -> bool {
        if let Ok(mut f) = fs::File::open(hash_file) {
            let mut buf = String::new();
            f.read_to_string(&mut buf).ok();
            if buf.parse::<u64>() == Ok(hash) {
                return false;
            }
        }
        true
    }

    fn write_hash(&self, hash_file: &Path, hash: u64) -> io::Result<()> {
        let mut f = fs::File::create(hash_file)?;
        f.write_all(hash.to_string().as_bytes())
    }

    fn apply_derive(&self, mut file: fs::File, text: Vec<u8>) -> io::Result<()> {
        let mut lines: VecDeque<Cow<'_, str>> = text
            .split(|&x| x == b'\n')
            .map(|x| String::from_utf8_lossy(x.strip_suffix(b"\r").unwrap_or(x)))
            .collect();

        let derive_re = Regex::new(r"^#\[derive\(([[[:word:]], ]+)\)\]$").unwrap();
        let type_re = Regex::new(r"^pub (?:enum|struct) ([[:word:]]+) \{$").unwrap();

        // UTF-8 BOM
        file.write_all(b"\xEF\xBB\xBF")?;

        // Remove all empty lines at the tail.
        while let Some(line) = lines.back() {
            if line.is_empty() {
                lines.pop_back();
            } else {
                break;
            }
        }

        while let Some(line) = lines.pop_front() {
            if let Some(cap) = derive_re.captures(&line) {
                let derived = cap[1].split(',').map(|x| x.trim()).collect::<Vec<&str>>();
                let mut traits = derived.clone();
                for next_line in lines.iter() {
                    if let Some(cap) = type_re.captures(next_line) {
                        for ty in ["", &cap[1]] {
                            if let Some(derive) = self.derive.get(ty) {
                                for pattern in derive {
                                    if let Some(tr) = pattern.strip_prefix('-') {
                                        if let Some(i) = traits.iter().position(|&x| x == tr) {
                                            traits.remove(i);
                                        }
                                    } else {
                                        let tr = pattern.strip_prefix('+').unwrap_or(pattern);
                                        if !traits.contains(&tr)
                                            && (derived.contains(&tr) || !self.is_auto_derive(tr))
                                        {
                                            traits.push(tr);
                                        }
                                    }
                                }
                            }
                        }
                        break;
                    }
                }
                if !traits.is_empty() {
                    file.write_all(format!("#[derive({})]", traits.join(", ")).as_bytes())?;
                } else {
                    traits.sort();
                    file.write_all(b"// No derivation")?;
                }
            } else {
                file.write_all(line.as_bytes())?;
            }
            file.write_all(b"\n")?;
        }
        Ok(())
    }

    fn is_auto_derive(&self, trait_: &str) -> bool {
        self.derive
            .get("")
            .map(|x| x.iter().any(|x| x == trait_))
            .unwrap_or(false)
            && [
                "Copy",
                "Debug",
                "Default",
                "Hash",
                "PartialOrd",
                "Ord",
                "PartialEq",
                "Eq",
            ]
            .contains(&trait_)
    }

    fn norm_path<P: AsRef<Path>>(path: P) -> String {
        path.as_ref().to_string_lossy().as_ref().replace('\\', "/")
    }

    fn default_builder() -> bindgen::Builder {
        bindgen::Builder::default()
            .disable_header_comment()
            .layout_tests(false)
            .formatter(bindgen::Formatter::Rustfmt)
            .prepend_enum_name(false)
            .size_t_is_usize(true)
    }
}