oxirs-core 0.2.2

//! WebAssembly compilation for client-side SPARQL execution
//!
//! This module provides WASM compilation of SPARQL queries for efficient
//! client-side execution in web browsers and edge environments.

use crate::model::Variable;
use crate::query::plan::ExecutionPlan;
use crate::OxirsError;
use std::collections::HashMap;
use std::sync::{Arc, RwLock};

/// WASM query compiler
pub struct WasmQueryCompiler {
    /// Compilation cache
    cache: Arc<RwLock<CompilationCache>>,
    /// Target configuration
    target: WasmTarget,
    /// Optimization level
    optimization: OptimizationLevel,
}

/// WASM compilation target
#[derive(Debug, Clone)]
pub enum WasmTarget {
    /// Standard WASM 1.0
    Wasm1_0,
    /// WASM with SIMD extensions
    WasmSimd,
    /// WASM with threads (SharedArrayBuffer)
    WasmThreads,
    /// WASM with both SIMD and threads
    WasmSimdThreads,
    /// WASM with GC proposal
    WasmGC,
}

/// Optimization level for WASM compilation
#[derive(Debug, Clone, Copy, PartialEq, PartialOrd)]
pub enum OptimizationLevel {
    /// No optimizations
    None,
    /// Basic optimizations
    Basic,
    /// Standard optimizations
    Standard,
    /// Aggressive optimizations
    Aggressive,
    /// Size optimizations
    Size,
}

/// Compilation cache
struct CompilationCache {
    /// Cached modules
    modules: HashMap<QueryHash, CachedModule>,
    /// Total cache size in bytes
    total_size: usize,
    /// Maximum cache size
    max_size: usize,
}

/// Query hash for caching
type QueryHash = u64;

/// Cached WASM module
struct CachedModule {
    /// Compiled WASM bytes
    wasm_bytes: Vec<u8>,
    /// Module metadata
    #[allow(dead_code)]
    metadata: ModuleMetadata,
    /// Compilation time
    #[allow(dead_code)]
    compile_time: std::time::Duration,
    /// Usage count
    usage_count: usize,
}

/// WASM module metadata
#[derive(Debug, Clone)]
pub struct ModuleMetadata {
    /// Module size in bytes
    pub size: usize,
    /// Memory requirements
    pub memory_pages: u32,
    /// Exported functions
    pub exports: Vec<ExportedFunction>,
    /// Required imports
    pub imports: Vec<RequiredImport>,
    /// Optimization statistics
    pub optimization_stats: OptimizationStats,
}

/// Exported WASM function
#[derive(Debug, Clone)]
pub struct ExportedFunction {
    /// Function name
    pub name: String,
    /// Parameter types
    pub params: Vec<WasmType>,
    /// Return types
    pub returns: Vec<WasmType>,
    /// Function kind
    pub kind: FunctionKind,
}

/// WASM value types
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum WasmType {
    I32,
    I64,
    F32,
    F64,
    V128,      // SIMD vector
    FuncRef,   // Function reference
    ExternRef, // External reference
}

/// Function kinds
#[derive(Debug, Clone, PartialEq)]
pub enum FunctionKind {
    /// Main query execution
    QueryExec,
    /// Triple matching
    TripleMatch,
    /// Join operation
    Join,
    /// Filter evaluation
    Filter,
    /// Aggregation
    Aggregate,
    /// Helper function
    Helper(String),
}

/// Required import for WASM module
#[derive(Debug, Clone)]
pub struct RequiredImport {
    /// Module name
    pub module: String,
    /// Import name
    pub name: String,
    /// Import type
    pub import_type: ImportType,
}

/// Import types
#[derive(Debug, Clone)]
pub enum ImportType {
    /// Function import
    Function {
        params: Vec<WasmType>,
        returns: Vec<WasmType>,
    },
    /// Memory import
    Memory {
        min_pages: u32,
        max_pages: Option<u32>,
    },
    /// Table import
    Table {
        element_type: WasmType,
        min_size: u32,
        max_size: Option<u32>,
    },
    /// Global import
    Global { value_type: WasmType, mutable: bool },
}

/// Optimization statistics
#[derive(Debug, Clone, Default)]
pub struct OptimizationStats {
    /// Instructions eliminated
    pub instructions_eliminated: usize,
    /// Functions inlined
    pub functions_inlined: usize,
    /// Dead code removed
    pub dead_code_removed: usize,
    /// Loop optimizations
    pub loops_optimized: usize,
    /// Memory accesses optimized
    pub memory_optimizations: usize,
}

/// WASM runtime interface
pub trait WasmRuntime: Send + Sync {
    /// Instantiate WASM module
    fn instantiate(&self, wasm_bytes: &[u8]) -> Result<Box<dyn WasmInstance>, OxirsError>;

    /// Validate WASM module
    fn validate(&self, wasm_bytes: &[u8]) -> Result<(), OxirsError>;

    /// Get runtime capabilities
    fn capabilities(&self) -> RuntimeCapabilities;
}

/// WASM module instance
pub trait WasmInstance: Send + Sync {
    /// Execute query
    fn execute_query(&mut self, input: &QueryInput) -> Result<QueryOutput, OxirsError>;

    /// Get memory usage
    fn memory_usage(&self) -> usize;

    /// Reset instance state
    fn reset(&mut self);
}

/// Runtime capabilities
#[derive(Debug, Clone)]
pub struct RuntimeCapabilities {
    /// Supports SIMD
    pub simd: bool,
    /// Supports threads
    pub threads: bool,
    /// Supports bulk memory operations
    pub bulk_memory: bool,
    /// Supports reference types
    pub reference_types: bool,
    /// Maximum memory pages
    pub max_memory_pages: u32,
}

/// Query input for WASM execution
pub struct QueryInput {
    /// Serialized RDF data
    pub data: Vec<u8>,
    /// Variable bindings
    pub bindings: HashMap<String, Vec<u8>>,
    /// Execution limits
    pub limits: ExecutionLimits,
}

/// Query output from WASM execution
pub struct QueryOutput {
    /// Result bindings
    pub results: Vec<u8>,
    /// Execution statistics
    pub stats: ExecutionStats,
}

/// Execution limits
#[derive(Debug, Clone)]
pub struct ExecutionLimits {
    /// Maximum execution time in milliseconds
    pub timeout_ms: u32,
    /// Maximum memory usage in bytes
    pub max_memory: usize,
    /// Maximum result count
    pub max_results: usize,
}

/// Execution statistics
#[derive(Debug, Clone)]
pub struct ExecutionStats {
    /// Execution time in microseconds
    pub exec_time_us: u64,
    /// Memory used in bytes
    pub memory_used: usize,
    /// Triples scanned
    pub triples_scanned: usize,
    /// Results produced
    pub results_count: usize,
}

impl WasmQueryCompiler {
    /// Create new WASM compiler
    pub fn new(target: WasmTarget, optimization: OptimizationLevel) -> Self {
        Self {
            cache: Arc::new(RwLock::new(CompilationCache::new())),
            target,
            optimization,
        }
    }

    /// Compile query to WASM
    pub fn compile(&self, plan: &ExecutionPlan) -> Result<Vec<u8>, OxirsError> {
        let hash = self.hash_plan(plan);

        // Check cache
        if let Some(module) = self.get_cached(hash) {
            return Ok(module);
        }

        // Generate WASM
        let wasm_bytes = self.generate_wasm(plan)?;

        // Optimize
        let optimized = self.optimize_wasm(wasm_bytes)?;

        // Cache result
        self.cache_module(hash, optimized.clone())?;

        Ok(optimized)
    }

    /// Generate WASM module from execution plan
    fn generate_wasm(&self, plan: &ExecutionPlan) -> Result<Vec<u8>, OxirsError> {
        let mut builder = WasmModuleBuilder::new(self.target.clone());

        // Add memory
        builder.add_memory(1, Some(1024))?; // 1-1024 pages

        // Add imports
        self.add_imports(&mut builder)?;

        // Add data structures
        self.add_data_structures(&mut builder)?;

        // Generate query execution function
        self.generate_query_function(&mut builder, plan)?;

        // Generate helper functions
        self.generate_helpers(&mut builder)?;

        // Build module
        builder.build()
    }

    /// Add required imports
    fn add_imports(&self, builder: &mut WasmModuleBuilder) -> Result<(), OxirsError> {
        // Import host functions
        builder.add_import(
            "host",
            "alloc",
            ImportType::Function {
                params: vec![WasmType::I32],
                returns: vec![WasmType::I32],
            },
        )?;

        builder.add_import(
            "host",
            "free",
            ImportType::Function {
                params: vec![WasmType::I32],
                returns: vec![],
            },
        )?;

        builder.add_import(
            "host",
            "log",
            ImportType::Function {
                params: vec![WasmType::I32, WasmType::I32],
                returns: vec![],
            },
        )?;

        Ok(())
    }

    /// Add data structures
    fn add_data_structures(&self, builder: &mut WasmModuleBuilder) -> Result<(), OxirsError> {
        // Define term structure
        builder.add_struct(
            "Term",
            vec![
                ("kind", WasmType::I32),
                ("value_ptr", WasmType::I32),
                ("value_len", WasmType::I32),
                ("datatype_ptr", WasmType::I32),
                ("datatype_len", WasmType::I32),
                ("lang_ptr", WasmType::I32),
                ("lang_len", WasmType::I32),
            ],
        )?;

        // Define triple structure
        builder.add_struct(
            "Triple",
            vec![
                ("subject", WasmType::I32),
                ("predicate", WasmType::I32),
                ("object", WasmType::I32),
            ],
        )?;

        // Define binding structure
        builder.add_struct(
            "Binding",
            vec![
                ("var_ptr", WasmType::I32),
                ("var_len", WasmType::I32),
                ("term", WasmType::I32),
            ],
        )?;

        Ok(())
    }

    /// Generate main query function
    fn generate_query_function(
        &self,
        builder: &mut WasmModuleBuilder,
        plan: &ExecutionPlan,
    ) -> Result<(), OxirsError> {
        match plan {
            ExecutionPlan::TripleScan { pattern } => {
                self.generate_triple_scan(builder, pattern)?;
            }
            ExecutionPlan::HashJoin {
                left,
                right,
                join_vars,
            } => {
                self.generate_hash_join(builder, left, right, join_vars)?;
            }
            _ => {
                return Err(OxirsError::Query(
                    "Unsupported plan type for WASM".to_string(),
                ))
            }
        }

        Ok(())
    }

    /// Generate triple scan function
    fn generate_triple_scan(
        &self,
        builder: &mut WasmModuleBuilder,
        _pattern: &crate::model::pattern::TriplePattern,
    ) -> Result<(), OxirsError> {
        builder.add_function(
            "query_exec",
            vec![
                WasmType::I32, // input data pointer
                WasmType::I32, // input data length
                WasmType::I32, // output buffer pointer
                WasmType::I32, // output buffer length
            ],
            vec![WasmType::I32],
            |fb| {
                // Function body would be generated here
                // This is a simplified placeholder
                fb.local_get(0);
                fb.local_get(1);
                fb.call("scan_triples");
                fb.i32_const(0); // Return success
            },
        )?;

        Ok(())
    }

    /// Generate hash join function
    fn generate_hash_join(
        &self,
        builder: &mut WasmModuleBuilder,
        left: &ExecutionPlan,
        right: &ExecutionPlan,
        _join_vars: &[Variable],
    ) -> Result<(), OxirsError> {
        // Generate left and right sub-plans
        self.generate_query_function(builder, left)?;
        self.generate_query_function(builder, right)?;

        // Generate join function
        builder.add_function(
            "hash_join",
            vec![
                WasmType::I32, // left results
                WasmType::I32, // right results
                WasmType::I32, // join variables
                WasmType::I32, // output buffer
            ],
            vec![WasmType::I32],
            |fb| {
                // Hash join implementation
                fb.i32_const(0);
            },
        )?;

        Ok(())
    }

    /// Generate helper functions
    fn generate_helpers(&self, builder: &mut WasmModuleBuilder) -> Result<(), OxirsError> {
        // String comparison
        builder.add_function(
            "str_eq",
            vec![
                WasmType::I32,
                WasmType::I32, // str1 ptr, len
                WasmType::I32,
                WasmType::I32, // str2 ptr, len
            ],
            vec![WasmType::I32],
            |fb| {
                // Compare lengths first
                fb.local_get(1);
                fb.local_get(3);
                fb.i32_ne();
                fb.if_else(
                    WasmType::I32,
                    |fb| {
                        fb.i32_const(0); // Different lengths
                    },
                    |fb| {
                        // Compare bytes
                        fb.i32_const(1); // Placeholder
                    },
                );
            },
        )?;

        // Term matching
        builder.add_function(
            "match_term",
            vec![
                WasmType::I32, // term1
                WasmType::I32, // term2
            ],
            vec![WasmType::I32],
            |fb| {
                fb.i32_const(1); // Placeholder
            },
        )?;

        Ok(())
    }

    /// Optimize WASM module
    fn optimize_wasm(&self, wasm_bytes: Vec<u8>) -> Result<Vec<u8>, OxirsError> {
        match self.optimization {
            OptimizationLevel::None => Ok(wasm_bytes),
            _ => {
                // Would use wasm-opt or similar
                Ok(wasm_bytes)
            }
        }
    }

    /// Hash execution plan
    fn hash_plan(&self, plan: &ExecutionPlan) -> QueryHash {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

        let mut hasher = DefaultHasher::new();
        format!("{plan:?}").hash(&mut hasher);
        hasher.finish()
    }

    /// Get cached module
    fn get_cached(&self, hash: QueryHash) -> Option<Vec<u8>> {
        let cache = self.cache.read().ok()?;
        cache.modules.get(&hash).map(|m| m.wasm_bytes.clone())
    }

    /// Cache compiled module
    fn cache_module(&self, hash: QueryHash, wasm_bytes: Vec<u8>) -> Result<(), OxirsError> {
        let mut cache = self
            .cache
            .write()
            .map_err(|_| OxirsError::Query("Failed to acquire cache lock".to_string()))?;

        let metadata = ModuleMetadata {
            size: wasm_bytes.len(),
            memory_pages: 1,
            exports: vec![],
            imports: vec![],
            optimization_stats: OptimizationStats::default(),
        };

        cache.add(
            hash,
            CachedModule {
                wasm_bytes,
                metadata,
                compile_time: std::time::Duration::from_millis(10),
                usage_count: 0,
            },
        );

        Ok(())
    }
}

/// WASM module builder
struct WasmModuleBuilder {
    #[allow(dead_code)]
    target: WasmTarget,
    imports: Vec<RequiredImport>,
    functions: Vec<FunctionDef>,
    memory: Option<MemoryDef>,
    structs: Vec<StructDef>,
}

/// Function definition
struct FunctionDef {
    #[allow(dead_code)]
    name: String,
    #[allow(dead_code)]
    params: Vec<WasmType>,
    #[allow(dead_code)]
    returns: Vec<WasmType>,
    #[allow(dead_code)]
    body: Vec<WasmInstruction>,
}

/// Memory definition
struct MemoryDef {
    #[allow(dead_code)]
    min_pages: u32,
    #[allow(dead_code)]
    max_pages: Option<u32>,
}

/// Structure definition
struct StructDef {
    #[allow(dead_code)]
    name: String,
    #[allow(dead_code)]
    fields: Vec<(String, WasmType)>,
}

/// WASM instructions (simplified)
#[allow(dead_code)]
enum WasmInstruction {
    LocalGet(u32),
    LocalSet(u32),
    I32Const(i32),
    I32Add,
    I32Sub,
    I32Eq,
    I32Ne,
    Call(String),
    If(Vec<WasmInstruction>),
    IfElse(WasmType, Vec<WasmInstruction>, Vec<WasmInstruction>),
    Return,
}

/// Function builder for WASM generation
struct FunctionBuilder {
    instructions: Vec<WasmInstruction>,
}

impl FunctionBuilder {
    fn new() -> Self {
        Self {
            instructions: Vec::new(),
        }
    }

    fn local_get(&mut self, idx: u32) {
        self.instructions.push(WasmInstruction::LocalGet(idx));
    }

    #[allow(dead_code)]
    fn local_set(&mut self, idx: u32) {
        self.instructions.push(WasmInstruction::LocalSet(idx));
    }

    fn i32_const(&mut self, val: i32) {
        self.instructions.push(WasmInstruction::I32Const(val));
    }

    #[allow(dead_code)]
    fn i32_add(&mut self) {
        self.instructions.push(WasmInstruction::I32Add);
    }

    fn i32_ne(&mut self) {
        self.instructions.push(WasmInstruction::I32Ne);
    }

    fn call(&mut self, func: &str) {
        self.instructions
            .push(WasmInstruction::Call(func.to_string()));
    }

    fn if_else<F1, F2>(&mut self, result_type: WasmType, then_fn: F1, else_fn: F2)
    where
        F1: FnOnce(&mut Self),
        F2: FnOnce(&mut Self),
    {
        let mut then_builder = FunctionBuilder::new();
        then_fn(&mut then_builder);

        let mut else_builder = FunctionBuilder::new();
        else_fn(&mut else_builder);

        self.instructions.push(WasmInstruction::IfElse(
            result_type,
            then_builder.instructions,
            else_builder.instructions,
        ));
    }
}

impl WasmModuleBuilder {
    fn new(target: WasmTarget) -> Self {
        Self {
            target,
            imports: Vec::new(),
            functions: Vec::new(),
            memory: None,
            structs: Vec::new(),
        }
    }

    fn add_import(
        &mut self,
        module: &str,
        name: &str,
        import_type: ImportType,
    ) -> Result<(), OxirsError> {
        self.imports.push(RequiredImport {
            module: module.to_string(),
            name: name.to_string(),
            import_type,
        });
        Ok(())
    }

    fn add_memory(&mut self, min: u32, max: Option<u32>) -> Result<(), OxirsError> {
        self.memory = Some(MemoryDef {
            min_pages: min,
            max_pages: max,
        });
        Ok(())
    }

    fn add_struct(&mut self, name: &str, fields: Vec<(&str, WasmType)>) -> Result<(), OxirsError> {
        self.structs.push(StructDef {
            name: name.to_string(),
            fields: fields
                .into_iter()
                .map(|(n, t)| (n.to_string(), t))
                .collect(),
        });
        Ok(())
    }

    fn add_function<F>(
        &mut self,
        name: &str,
        params: Vec<WasmType>,
        returns: Vec<WasmType>,
        body_fn: F,
    ) -> Result<(), OxirsError>
    where
        F: FnOnce(&mut FunctionBuilder),
    {
        let mut builder = FunctionBuilder::new();
        body_fn(&mut builder);

        self.functions.push(FunctionDef {
            name: name.to_string(),
            params,
            returns,
            body: builder.instructions,
        });

        Ok(())
    }

    fn build(self) -> Result<Vec<u8>, OxirsError> {
        // Would generate actual WASM bytes
        // This is a placeholder
        Ok(vec![0x00, 0x61, 0x73, 0x6d]) // WASM magic number
    }
}

impl CompilationCache {
    fn new() -> Self {
        Self {
            modules: HashMap::new(),
            total_size: 0,
            max_size: 100 * 1024 * 1024, // 100MB
        }
    }

    fn add(&mut self, hash: QueryHash, module: CachedModule) {
        self.total_size += module.wasm_bytes.len();
        self.modules.insert(hash, module);

        // Evict if needed
        while self.total_size > self.max_size && !self.modules.is_empty() {
            // Remove least used
            if let Some((&hash, _)) = self.modules.iter().min_by_key(|(_, m)| m.usage_count) {
                if let Some(removed) = self.modules.remove(&hash) {
                    self.total_size -= removed.wasm_bytes.len();
                }
            }
        }
    }
}

/// Streaming WASM compiler for large queries
pub struct StreamingWasmCompiler {
    base_compiler: WasmQueryCompiler,
    chunk_size: usize,
}

impl StreamingWasmCompiler {
    /// Create new streaming compiler
    pub fn new(target: WasmTarget, optimization: OptimizationLevel) -> Self {
        Self {
            base_compiler: WasmQueryCompiler::new(target, optimization),
            chunk_size: 1024 * 1024, // 1MB chunks
        }
    }

    /// Compile query in streaming fashion
    pub async fn compile_streaming(
        &self,
        plan: &ExecutionPlan,
    ) -> Result<impl futures::Stream<Item = Result<Vec<u8>, OxirsError>> + use<>, OxirsError> {
        use futures::stream;

        // Generate full module
        let wasm_bytes = self.base_compiler.compile(plan)?;

        // Split into chunks
        let chunks: Vec<Vec<u8>> = wasm_bytes
            .chunks(self.chunk_size)
            .map(|c| c.to_vec())
            .collect();

        Ok(stream::iter(chunks.into_iter().map(Ok)))
    }
}

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

    #[test]
    fn test_wasm_compiler_creation() {
        let compiler = WasmQueryCompiler::new(WasmTarget::Wasm1_0, OptimizationLevel::Standard);

        let cache = compiler.cache.read().expect("lock should not be poisoned");
        assert_eq!(cache.modules.len(), 0);
    }

    #[test]
    fn test_module_builder() {
        let mut builder = WasmModuleBuilder::new(WasmTarget::Wasm1_0);

        builder
            .add_memory(1, Some(16))
            .expect("add memory should succeed");
        builder
            .add_import(
                "host",
                "log",
                ImportType::Function {
                    params: vec![WasmType::I32],
                    returns: vec![],
                },
            )
            .expect("operation should succeed");

        builder
            .add_function("test", vec![], vec![WasmType::I32], |fb| {
                fb.i32_const(42);
            })
            .expect("operation should succeed");

        let wasm = builder.build().expect("operation should succeed");
        assert!(!wasm.is_empty());
    }

    #[test]
    fn test_optimization_levels() {
        assert_eq!(OptimizationLevel::None as u8, 0);
        assert!(OptimizationLevel::Aggressive > OptimizationLevel::Standard);
    }
}