dampen-core 0.3.2

//! Handler inventory extraction for build scripts
//!
//! This module provides utilities for build.rs scripts to extract handler metadata
//! from Rust source files that use the `inventory_handlers!` macro.

use crate::HandlerSignature;
use std::path::Path;

/// Extract handler names from an `inventory_handlers!` macro invocation in a Rust file.
///
/// This function parses the source file and looks for the `inventory_handlers!` macro,
/// extracting the list of handler names declared within it.
///
/// # Arguments
///
/// * `rs_file_path` - Path to the .rs file to parse
///
/// # Returns
///
/// A vector of handler names found in the inventory, or an empty vector if:
/// - The file doesn't exist
/// - The file has no `inventory_handlers!` macro
/// - The macro is empty
///
/// # Example
///
/// ```rust,ignore
/// let handlers = extract_handler_names_from_file("src/ui/window.rs");
/// // Returns: vec!["increment", "decrement", "reset"]
/// ```
pub fn extract_handler_names_from_file(rs_file_path: &Path) -> Vec<String> {
    let content = match std::fs::read_to_string(rs_file_path) {
        Ok(content) => content,
        Err(_) => return vec![],
    };

    extract_handler_names_from_source(&content)
}

/// Extract handler names from Rust source code containing `inventory_handlers!` macro.
///
/// # Arguments
///
/// * `source` - Rust source code as a string
///
/// # Returns
///
/// A vector of handler names found in the inventory
fn extract_handler_names_from_source(source: &str) -> Vec<String> {
    // Parse the file with syn
    let syntax = match syn::parse_file(source) {
        Ok(syntax) => syntax,
        Err(_) => return vec![],
    };

    // Look for inventory_handlers! macro invocation
    for item in syntax.items {
        if let syn::Item::Macro(mac) = item {
            let path = &mac.mac.path;

            // Check if this is our inventory_handlers macro
            if path.segments.last().map(|s| s.ident.to_string())
                == Some("inventory_handlers".to_string())
            {
                // Parse the token stream to extract handler names
                return parse_handler_list_from_tokens(&mac.mac.tokens);
            }
        }
    }

    vec![]
}

/// Parse handler names from the token stream of inventory_handlers! macro.
fn parse_handler_list_from_tokens(tokens: &proc_macro2::TokenStream) -> Vec<String> {
    let mut handlers = Vec::new();
    let tokens_str = tokens.to_string();

    // Simple tokenization: split by commas and trim whitespace
    for part in tokens_str.split(',') {
        let name = part.trim().to_string();
        if !name.is_empty() {
            handlers.push(name);
        }
    }

    handlers
}

/// Extract full handler metadata from a Rust file.
///
/// This function looks for the `inventory_handlers!` macro to get handler names,
/// then analyzes the function signatures marked with `#[ui_handler]` to determine
/// their parameter and return types.
///
/// # Arguments
///
/// * `rs_file_path` - Path to the .rs file to parse
///
/// # Returns
///
/// A vector of HandlerSignature objects with complete metadata
pub fn extract_handler_signatures_from_file(rs_file_path: &Path) -> Vec<HandlerSignature> {
    let content = match std::fs::read_to_string(rs_file_path) {
        Ok(content) => content,
        Err(_) => return vec![],
    };

    let handler_names = extract_handler_names_from_source(&content);

    // Parse the file to extract function signatures
    let syntax = match syn::parse_file(&content) {
        Ok(syntax) => syntax,
        Err(_) => {
            // Fallback to simple signatures if parsing fails
            return handler_names
                .into_iter()
                .map(|name| HandlerSignature {
                    name,
                    param_type: None,
                    returns_command: false,
                })
                .collect();
        }
    };

    // Extract signatures for each handler by finding the corresponding function
    handler_names
        .into_iter()
        .map(|name| {
            // Look for the function with this name and #[ui_handler] attribute
            if let Some(signature) = find_handler_function_signature(&syntax, &name) {
                signature
            } else {
                // Fallback to simple signature
                HandlerSignature {
                    name,
                    param_type: None,
                    returns_command: false,
                }
            }
        })
        .collect()
}

/// Find a function with the given name and extract its signature
fn find_handler_function_signature(
    syntax: &syn::File,
    handler_name: &str,
) -> Option<HandlerSignature> {
    use syn::{FnArg, Item, ReturnType};

    for item in &syntax.items {
        if let Item::Fn(func) = item {
            // Check if this is the function we're looking for
            if func.sig.ident == handler_name {
                // Check if it has #[ui_handler] attribute
                let has_ui_handler_attr = func.attrs.iter().any(|attr| {
                    attr.path().segments.last().map(|s| s.ident.to_string())
                        == Some("ui_handler".to_string())
                });

                if !has_ui_handler_attr {
                    continue;
                }

                // Analyze the signature
                let mut param_type: Option<String> = None;
                let mut param_count = 0;

                for input in &func.sig.inputs {
                    if let FnArg::Typed(pat_type) = input {
                        param_count += 1;
                        // If there's more than one parameter (first is always &mut Model)
                        // then the second one is the value parameter
                        if param_count > 1 {
                            let ty = &pat_type.ty;
                            let type_str = quote::quote!(#ty).to_string();
                            // Clean up the type string (remove extra spaces)
                            param_type = Some(type_str.replace(" ", ""));
                        }
                    }
                }

                // Check if it returns Command
                let returns_command = if let ReturnType::Type(_, ty) = &func.sig.output {
                    let return_str = quote::quote!(#ty).to_string();
                    return_str.contains("Command")
                } else {
                    false
                };

                return Some(HandlerSignature {
                    name: handler_name.to_string(),
                    param_type,
                    returns_command,
                });
            }
        }
    }

    None
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_extract_handler_names() {
        let source = r#"
            use dampen_macros::{ui_handler, inventory_handlers};

            #[ui_handler]
            fn increment(model: &mut Model) {
                model.count += 1;
            }

            #[ui_handler]
            fn decrement(model: &mut Model) {
                model.count -= 1;
            }

            inventory_handlers! {
                increment,
                decrement
            }
        "#;

        let handlers = extract_handler_names_from_source(source);
        assert_eq!(handlers, vec!["increment", "decrement"]);
    }

    #[test]
    fn test_extract_empty_inventory() {
        let source = r#"
            use dampen_macros::ui_handler;

            #[ui_handler]
            fn my_handler(model: &mut Model) {}
        "#;

        let handlers = extract_handler_names_from_source(source);
        assert!(handlers.is_empty());
    }

    #[test]
    fn test_extract_single_handler() {
        let source = r#"
            inventory_handlers! { greet }
        "#;

        let handlers = extract_handler_names_from_source(source);
        assert_eq!(handlers, vec!["greet"]);
    }
}