//! nyash.toml v2 configuration parser
//! 
//! Ultimate simple design: nyash.toml-centric architecture + minimal FFI
//! No Host VTable, single entry point (nyash_plugin_invoke)

use serde::{Deserialize, Serialize};
use std::collections::HashMap;

/// Root configuration structure
#[derive(Debug, Deserialize, Serialize)]
pub struct NyashConfigV2 {
    /// Library definitions (multi-box capable)
    #[serde(default)]
    pub libraries: HashMap<String, LibraryDefinition>,
    
    /// Plugin search paths
    #[serde(default)]
    pub plugin_paths: PluginPaths,

    /// New: Plugins registry (name -> plugin root directory)
    #[serde(default)]
    pub plugins: HashMap<String, String>,

    /// Optional central type_id mapping (box name -> type_id)
    #[serde(default)]
    pub box_types: HashMap<String, u32>,
}

/// Library definition (simplified)
#[derive(Debug, Deserialize, Serialize)]
pub struct LibraryDefinition {
    /// Box types provided by this library
    pub boxes: Vec<String>,
    
    /// Path to the shared library
    pub path: String,
}

/// Plugin search paths
#[derive(Debug, Default, Deserialize, Serialize)]
pub struct PluginPaths {
    #[serde(default)]
    pub search_paths: Vec<String>,
}

/// Box type configuration (nested under library)
#[derive(Debug, Deserialize, Serialize)]
pub struct BoxTypeConfig {
    /// Box type ID
    pub type_id: u32,
    
    /// ABI version (default: 1)
    #[serde(default = "default_abi_version")]
    pub abi_version: u32,
    
    /// Method definitions
    pub methods: HashMap<String, MethodDefinition>,

    /// Singleton service flag (keep one shared instance alive in loader)
    #[serde(default)]
    pub singleton: bool,
}

/// Method definition (simplified - no argument info needed)
#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct MethodDefinition {
    /// Method ID for FFI
    pub method_id: u32,
    /// Optional argument declarations (v2.1+)
    #[serde(default)]
    pub args: Option<Vec<ArgDecl>>, 
    /// Optional: wrap return and errors into ResultBox when true
    #[serde(default)]
    pub returns_result: bool,
}

/// Method argument declaration (v2.1+)
#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(untagged)]
pub enum ArgDecl {
    /// Backward-compatible string form (treated as kind="string")
    Name(String),
    /// Typed declaration
    Typed {
        kind: String,
        #[serde(default)]
        category: Option<String>,
    },
}

impl ArgDecl {
    /// Returns a canonical kind string ("string", "box", etc.)
    pub fn kind_str(&self) -> &str {
        match self {
            ArgDecl::Name(_) => "string",
            ArgDecl::Typed { kind, .. } => kind.as_str(),
        }
    }
}

fn default_abi_version() -> u32 {
    1
}

impl NyashConfigV2 {
    /// Parse nyash.toml file
    pub fn from_file(path: &str) -> Result<Self, Box<dyn std::error::Error>> {
        let content = std::fs::read_to_string(path)?;
        Self::from_str(&content)
    }

    /// Parse nyash.toml content from string (test/helper)
    pub fn from_str(content: &str) -> Result<Self, Box<dyn std::error::Error>> {
        // Parse as raw TOML first to handle nested box configs
        let mut config: toml::Value = toml::from_str(content)?;

        // Extract library definitions
        let libraries = Self::parse_libraries(&mut config)?;

        // Extract plugin paths
        let plugin_paths = if let Some(paths) = config.get("plugin_paths") {
            paths.clone().try_into::<PluginPaths>()?
        } else {
            PluginPaths::default()
        };

        // Extract plugins map
        let plugins = if let Some(tbl) = config.get("plugins").and_then(|v| v.as_table()) {
            let mut m = HashMap::new();
            for (k, v) in tbl.iter() {
                if let Some(s) = v.as_str() { m.insert(k.clone(), s.to_string()); }
            }
            m
        } else { HashMap::new() };

        // Extract optional box_types map
        let box_types = if let Some(tbl) = config.get("box_types").and_then(|v| v.as_table()) {
            let mut m = HashMap::new();
            for (k, v) in tbl.iter() { if let Some(id) = v.as_integer() { m.insert(k.clone(), id as u32); } }
            m
        } else { HashMap::new() };

        Ok(NyashConfigV2 { libraries, plugin_paths, plugins, box_types })
    }
    
    /// Parse library definitions with nested box configs
    fn parse_libraries(config: &mut toml::Value) -> Result<HashMap<String, LibraryDefinition>, Box<dyn std::error::Error>> {
        let mut libraries = HashMap::new();
        
        if let Some(libs_section) = config.get("libraries").and_then(|v| v.as_table()) {
            for (lib_name, lib_value) in libs_section {
                if let Some(lib_table) = lib_value.as_table() {
                    let boxes = lib_table.get("boxes")
                        .and_then(|v| v.as_array())
                        .map(|arr| {
                            arr.iter()
                                .filter_map(|v| v.as_str())
                                .map(|s| s.to_string())
                                .collect()
                        })
                        .unwrap_or_default();
                    
                    let path = lib_table.get("path")
                        .and_then(|v| v.as_str())
                        .unwrap_or(lib_name)
                        .to_string();
                    
                    libraries.insert(lib_name.clone(), LibraryDefinition {
                        boxes,
                        path,
                    });
                }
            }
        }
        
        Ok(libraries)
    }
    
    /// Get box configuration from nested structure
    /// e.g., [libraries."libnyash_filebox_plugin.so".FileBox]
    pub fn get_box_config(&self, lib_name: &str, box_name: &str, config_value: &toml::Value) -> Option<BoxTypeConfig> {
        config_value
            .get("libraries")
            .and_then(|v| v.get(lib_name))
            .and_then(|v| v.get(box_name))
            .and_then(|v| v.clone().try_into::<BoxTypeConfig>().ok())
    }
    
    /// Find library that provides a specific box type
    pub fn find_library_for_box(&self, box_type: &str) -> Option<(&str, &LibraryDefinition)> {
        self.libraries.iter()
            .find(|(_, lib)| lib.boxes.contains(&box_type.to_string()))
            .map(|(name, lib)| (name.as_str(), lib))
    }
    
    /// Resolve plugin path from search paths
    pub fn resolve_plugin_path(&self, plugin_name: &str) -> Option<String> {
        // Try exact path first
        if std::path::Path::new(plugin_name).exists() {
            return Some(plugin_name.to_string());
        }
        // Build effective search paths: config + ENV:NYASH_PLUGIN_PATHS (sep=';' or ':')
        let mut paths: Vec<String> = Vec::new();
        paths.extend(self.plugin_paths.search_paths.iter().cloned());
        if let Ok(envp) = std::env::var("NYASH_PLUGIN_PATHS") {
            let sep = if cfg!(target_os = "windows") { ';' } else { ':' };
            for p in envp.split(sep).filter(|s| !s.is_empty()) { paths.push(p.to_string()); }
        }
        // Search in effective paths
        for search_path in &paths {
            let path = std::path::Path::new(search_path).join(plugin_name);
            if path.exists() {
                return Some(path.to_string_lossy().to_string());
            }
        }
        
        None
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn test_parse_v2_config() {
        let toml_str = r#"
[libraries]
[libraries."libnyash_filebox_plugin.so"]
boxes = ["FileBox"]
path = "./target/release/libnyash_filebox_plugin.so"

[libraries."libnyash_filebox_plugin.so".FileBox]
type_id = 6
abi_version = 1

[libraries."libnyash_filebox_plugin.so".FileBox.methods]
birth = { method_id = 0 }
open = { method_id = 1 }
close = { method_id = 4 }
"#;
        let nyash_config = NyashConfigV2::from_str(toml_str).unwrap();
        assert!(nyash_config.libraries.contains_key("libnyash_filebox_plugin.so"));
        let (lib_name, lib_def) = nyash_config.find_library_for_box("FileBox").unwrap();
        assert_eq!(lib_name, "libnyash_filebox_plugin.so");
        assert_eq!(lib_def.boxes, vec!["FileBox".to_string()]);
        // Nested box config should be retrievable
        let raw: toml::Value = toml::from_str(toml_str).unwrap();
        let box_conf = nyash_config.get_box_config("libnyash_filebox_plugin.so", "FileBox", &raw).unwrap();
        assert_eq!(box_conf.type_id, 6);
    }
}