//! 🚀 编译器级性能优化 - 极致编译时优化
//! 
//! 实现编译时的极致性能优化，包括：
//! - 编译器标志优化配置
//! - 编译时代码生成
//! - 内联优化和宏策略  
//! - 配置引导优化 (PGO)
//! - 链接时优化 (LTO)
//! - 目标特定CPU优化
//! - 常量求值优化
//! - 零成本抽象

use std::collections::HashMap;
use std::sync::atomic::{AtomicU64, Ordering};

use anyhow::Result;

/// 🚀 编译器优化配置器
pub struct CompilerOptimizer {
    /// 优化标志配置
    pub optimization_flags: OptimizationFlags,
    /// 代码生成配置
    pub codegen_config: CodegenConfig,
    /// 内联策略
    pub inline_strategy: InlineStrategy,
    /// 统计信息
    stats: CompilerOptimizationStats,
}

/// 编译器优化标志
#[derive(Debug, Clone)]
pub struct OptimizationFlags {
    /// 优化级别
    pub opt_level: OptLevel,
    /// 启用链接时优化
    pub enable_lto: bool,
    /// 启用配置引导优化
    pub enable_pgo: bool,
    /// 目标CPU
    pub target_cpu: String,
    /// 目标特性
    pub target_features: Vec<String>,
    /// 代码模型
    pub code_model: CodeModel,
    /// 启用调试信息
    pub debug_info: bool,
    /// 启用增量编译
    pub incremental: bool,
    /// 并发编译单元数
    pub codegen_units: Option<usize>,
}

/// 优化级别
#[derive(Debug, Clone)]
pub enum OptLevel {
    /// 无优化
    None,
    /// 基本优化
    Less,
    /// 默认优化
    Default,
    /// 积极优化
    Aggressive,
    /// 大小优化
    Size,
    /// 极致大小优化
    SizeZ,
}

/// 代码模型
#[derive(Debug, Clone)]
pub enum CodeModel {
    /// 小代码模型
    Small,
    /// 内核代码模型
    Kernel,
    /// 中等代码模型
    Medium,
    /// 大代码模型
    Large,
}

/// 代码生成配置
#[derive(Debug, Clone)]
pub struct CodegenConfig {
    /// 启用恐慌即中止
    pub panic_abort: bool,
    /// 溢出检查
    pub overflow_checks: bool,
    /// 启用胖指针LTO
    pub fat_lto: bool,
    /// 启用SIMD
    pub enable_simd: bool,
    /// 启用向量化
    pub enable_vectorization: bool,
    /// 启用循环展开
    pub enable_loop_unrolling: bool,
    /// 最大循环展开次数
    pub max_unroll_count: usize,
    /// 启用分支预测优化
    pub enable_branch_prediction: bool,
}

/// 内联策略
#[derive(Debug, Clone)]
pub struct InlineStrategy {
    /// 内联阈值
    pub inline_threshold: usize,
    /// 强制内联标记
    pub force_inline_hot_paths: bool,
    /// 禁用内联冷路径
    pub no_inline_cold_paths: bool,
    /// 启用跨crate内联
    pub cross_crate_inline: bool,
}

/// 编译器优化统计
#[derive(Debug, Default)]
pub struct CompilerOptimizationStats {
    /// 内联函数计数
    pub inlined_functions: AtomicU64,
    /// 常量折叠次数
    pub constant_folding: AtomicU64,
    /// 死代码消除次数
    pub dead_code_elimination: AtomicU64,
    /// 循环优化次数
    pub loop_optimizations: AtomicU64,
}

impl CompilerOptimizer {
    /// 创建编译器优化器
    pub fn new() -> Self {
        Self {
            optimization_flags: OptimizationFlags::ultra_performance(),
            codegen_config: CodegenConfig::ultra_performance(),
            inline_strategy: InlineStrategy::aggressive(),
            stats: CompilerOptimizationStats::default(),
        }
    }
    
    /// 🚀 生成超高性能编译配置
    pub fn generate_ultra_performance_config(&self) -> Result<CompilerConfig> {
        log::info!("🚀 Generating ultra-performance compiler configuration...");
        
        let mut rustflags = Vec::new();
        
        // 基础优化标志
        rustflags.push("-C".to_string());
        rustflags.push("opt-level=3".to_string()); // 最高优化级别
        
        // 链接时优化
        if self.optimization_flags.enable_lto {
            rustflags.push("-C".to_string());
            rustflags.push("lto=fat".to_string()); // 胖LTO获得最佳优化
        }
        
        // 目标CPU优化
        if !self.optimization_flags.target_cpu.is_empty() {
            rustflags.push("-C".to_string());
            rustflags.push(format!("target-cpu={}", self.optimization_flags.target_cpu));
        }
        
        // 目标特性
        if !self.optimization_flags.target_features.is_empty() {
            rustflags.push("-C".to_string());
            rustflags.push(format!("target-feature={}", self.optimization_flags.target_features.join(",")));
        }
        
        // 代码模型
        rustflags.push("-C".to_string());
        rustflags.push(format!("code-model={:?}", self.optimization_flags.code_model).to_lowercase());
        
        // 恐慌处理
        if self.codegen_config.panic_abort {
            rustflags.push("-C".to_string());
            rustflags.push("panic=abort".to_string());
        }
        
        // 溢出检查
        if !self.codegen_config.overflow_checks {
            rustflags.push("-C".to_string());
            rustflags.push("overflow-checks=no".to_string());
        }
        
        // 代码生成单元
        if let Some(units) = self.optimization_flags.codegen_units {
            rustflags.push("-C".to_string());
            rustflags.push(format!("codegen-units={}", units));
        }
        
        // 内联阈值
        rustflags.push("-C".to_string());
        rustflags.push(format!("inline-threshold={}", self.inline_strategy.inline_threshold));
        
        // 额外的性能优化标志
        rustflags.extend([
            "-C".to_string(), "embed-bitcode=no".to_string(), // 不嵌入位码以减少体积
            "-C".to_string(), "debuginfo=0".to_string(), // 禁用调试信息
            "-C".to_string(), "rpath=no".to_string(), // 禁用rpath
            "-C".to_string(), "force-frame-pointers=no".to_string(), // 禁用帧指针
        ]);
        
        let config = CompilerConfig {
            rustflags,
            env_vars: self.generate_env_vars(),
            cargo_config: self.generate_cargo_config(),
        };
        
        log::info!("✅ Ultra-performance compiler configuration generated");
        Ok(config)
    }
    
    /// 生成环境变量配置
    fn generate_env_vars(&self) -> HashMap<String, String> {
        let mut env_vars = HashMap::new();
        
        // CPU特定优化
        env_vars.insert("CARGO_CFG_TARGET_FEATURE".to_string(), 
                       self.optimization_flags.target_features.join(","));
        
        // 启用不稳定特性
        env_vars.insert("RUSTC_BOOTSTRAP".to_string(), "1".to_string());
        
        // 编译缓存设置
        if self.optimization_flags.incremental {
            env_vars.insert("CARGO_INCREMENTAL".to_string(), "1".to_string());
        } else {
            env_vars.insert("CARGO_INCREMENTAL".to_string(), "0".to_string());
        }
        
        env_vars
    }
    
    /// 生成Cargo配置
    fn generate_cargo_config(&self) -> CargoConfig {
        CargoConfig {
            profile_release: ProfileConfig {
                opt_level: 3,
                lto: self.optimization_flags.enable_lto,
                codegen_units: self.optimization_flags.codegen_units.unwrap_or(1),
                panic: if self.codegen_config.panic_abort { "abort" } else { "unwind" }.to_string(),
                overflow_checks: self.codegen_config.overflow_checks,
                debug: false,
                debug_assertions: false,
                rpath: false,
                strip: true, // 去除符号表
            }
        }
    }
    
    /// 获取统计信息
    pub fn get_stats(&self) -> CompilerOptimizationStats {
        CompilerOptimizationStats {
            inlined_functions: AtomicU64::new(self.stats.inlined_functions.load(Ordering::Relaxed)),
            constant_folding: AtomicU64::new(self.stats.constant_folding.load(Ordering::Relaxed)),
            dead_code_elimination: AtomicU64::new(self.stats.dead_code_elimination.load(Ordering::Relaxed)),
            loop_optimizations: AtomicU64::new(self.stats.loop_optimizations.load(Ordering::Relaxed)),
        }
    }
}

impl OptimizationFlags {
    /// 超高性能配置
    pub fn ultra_performance() -> Self {
        #[cfg(target_arch = "x86_64")]
        let target_features = vec![
            "+sse4.2".to_string(),
            "+avx".to_string(),
            "+avx2".to_string(),
            "+fma".to_string(),
            "+bmi1".to_string(),
            "+bmi2".to_string(),
            "+lzcnt".to_string(),
            "+popcnt".to_string(),
        ];

        #[cfg(not(target_arch = "x86_64"))]
        let target_features = vec![];
        Self {
            opt_level: OptLevel::Aggressive,
            enable_lto: true,
            enable_pgo: false, // PGO需要多阶段构建
            target_cpu: "native".to_string(), // 使用本机CPU特性
            target_features,
            code_model: CodeModel::Small,
            debug_info: false,
            incremental: false, // 发布版本禁用增量编译
            codegen_units: Some(1), // 单个代码生成单元获得最佳优化
        }
    }
}

impl CodegenConfig {
    /// 超高性能配置
    pub fn ultra_performance() -> Self {
        Self {
            panic_abort: true, // 恐慌即中止，避免展开开销
            overflow_checks: false, // 生产环境禁用溢出检查
            fat_lto: true,
            enable_simd: true,
            enable_vectorization: true,
            enable_loop_unrolling: true,
            max_unroll_count: 16,
            enable_branch_prediction: true,
        }
    }
}

impl InlineStrategy {
    /// 激进内联策略
    pub fn aggressive() -> Self {
        Self {
            inline_threshold: 1000, // 更高的内联阈值
            force_inline_hot_paths: true,
            no_inline_cold_paths: true,
            cross_crate_inline: true,
        }
    }
}

/// 编译器配置
#[derive(Debug, Clone)]
pub struct CompilerConfig {
    pub rustflags: Vec<String>,
    pub env_vars: HashMap<String, String>,
    pub cargo_config: CargoConfig,
}

/// Cargo配置
#[derive(Debug, Clone)]
pub struct CargoConfig {
    pub profile_release: ProfileConfig,
}

/// Profile配置
#[derive(Debug, Clone)]
pub struct ProfileConfig {
    pub opt_level: u8,
    pub lto: bool,
    pub codegen_units: usize,
    pub panic: String,
    pub overflow_checks: bool,
    pub debug: bool,
    pub debug_assertions: bool,
    pub rpath: bool,
    pub strip: bool,
}

/// 🚀 编译时优化宏
#[macro_export]
macro_rules! compile_time_optimize {
    // 编译时常量计算
    (const $expr:expr) => {
        const { $expr }
    };
    
    // 强制内联热路径
    (inline_hot $fn_name:ident) => {
        #[inline(always)]
        #[hot]
        $fn_name
    };
    
    // 标记冷路径
    (cold $fn_name:ident) => {
        #[inline(never)]
        #[cold]
        $fn_name
    };
}

/// 🚀 零成本抽象特征
pub trait ZeroCostAbstraction {
    type Output;
    
    /// 编译时计算
    fn compute_at_compile_time(&self) -> Self::Output;
    
    /// 内联操作
    #[inline(always)]
    fn inline_operation(&self) -> Self::Output {
        self.compute_at_compile_time()
    }
}

/// 🚀 编译时优化的快速事件处理器
pub struct CompileTimeOptimizedEventProcessor {
    /// 预计算的哈希表
    hash_table: [u64; 256],
    /// 预计算的路由表
    route_table: [u32; 1024],
}

impl CompileTimeOptimizedEventProcessor {
    /// 创建编译时优化的处理器
    pub const fn new() -> Self {
        Self {
            hash_table: Self::precompute_hash_table(),
            route_table: Self::precompute_route_table(),
        }
    }
    
    /// 编译时预计算哈希表
    const fn precompute_hash_table() -> [u64; 256] {
        let mut table = [0u64; 256];
        let mut i = 0;
        
        while i < 256 {
            // 使用编译时常量计算哈希值
            table[i] = Self::const_hash(i as u8);
            i += 1;
        }
        
        table
    }
    
    /// 编译时预计算路由表
    const fn precompute_route_table() -> [u32; 1024] {
        let mut table = [0u32; 1024];
        let mut i = 0;
        
        while i < 1024 {
            // 预计算路由信息
            table[i] = (i as u32) % 16; // 16个工作线程
            i += 1;
        }
        
        table
    }
    
    /// 编译时常量哈希函数
    const fn const_hash(input: u8) -> u64 {
        // 使用简单的编译时常量哈希
        let mut hash = input as u64;
        hash ^= hash << 13;
        hash ^= hash >> 7;
        hash ^= hash << 17;
        hash
    }
    
    /// 🚀 零开销事件路由
    #[inline(always)]
    pub fn route_event_zero_cost(&self, event_id: u8) -> u32 {
        // 编译时优化：直接数组访问，无边界检查
        unsafe {
            *self.route_table.get_unchecked((event_id as usize) & 1023)
        }
    }
    
    /// 🚀 编译时优化的哈希查找
    #[inline(always)]
    pub fn hash_lookup_optimized(&self, key: u8) -> u64 {
        // 编译器会将这个优化为直接内存访问
        self.hash_table[key as usize]
    }
}

/// 🚀 SIMD编译时优化
pub struct SIMDCompileTimeOptimizer;

impl SIMDCompileTimeOptimizer {
    /// 编译时SIMD向量化 - x86_64 AVX2 版本
    #[cfg(target_arch = "x86_64")]
    #[target_feature(enable = "avx2")]
    pub unsafe fn vectorized_sum_compile_time(data: &[u64]) -> u64 {
        use std::arch::x86_64::*;
        
        if data.len() < 4 {
            return data.iter().sum();
        }
        
        let chunks = data.len() / 4;
        let mut sum_vec = _mm256_setzero_si256();
        
        for i in 0..chunks {
            let ptr = data.as_ptr().add(i * 4) as *const __m256i;
            let vec = _mm256_loadu_si256(ptr);
            sum_vec = _mm256_add_epi64(sum_vec, vec);
        }
        
        // 水平求和
        let mut result = [0u64; 4];
        _mm256_storeu_si256(result.as_mut_ptr() as *mut __m256i, sum_vec);
        let partial_sum: u64 = result.iter().sum();
        
        // 处理剩余元素
        let remaining: u64 = data[chunks * 4..].iter().sum();
        
        partial_sum + remaining
    }

    /// 编译时SIMD向量化 - 通用回退版本（非x86_64架构）
    #[cfg(not(target_arch = "x86_64"))]
    pub fn vectorized_sum_compile_time(data: &[u64]) -> u64 {
        data.iter().sum()
    }
}

/// 🚀 生成优化构建脚本
pub fn generate_build_script() -> String {
    r#"
fn main() {
    // 编译时CPU特性检测
    if is_x86_feature_detected!("avx2") {
        println!("cargo:rustc-cfg=has_avx2");
    }
    
    if is_x86_feature_detected!("avx512f") {
        println!("cargo:rustc-cfg=has_avx512");
    }
    
    // 编译时目标特性启用
    println!("cargo:rustc-env=TARGET_FEATURE=+sse4.2,+avx,+avx2,+fma");
    
    // 链接时优化
    println!("cargo:rustc-link-arg=-fuse-ld=lld"); // 使用更快的链接器
    
    // 编译时常量配置
    println!("cargo:rustc-env=COMPILE_TIME_OPTIMIZED=1");
    
    // Profile引导优化设置
    if std::env::var("ENABLE_PGO").is_ok() {
        println!("cargo:rustc-link-arg=-fprofile-use");
    }
}
"#.to_string()
}

/// 🚀 生成.cargo/config.toml
pub fn generate_cargo_config_toml() -> String {
    r#"
[build]
rustflags = [
    "-C", "opt-level=3",
    "-C", "lto=fat",
    "-C", "panic=abort",
    "-C", "codegen-units=1",
    "-C", "target-cpu=native",
    "-C", "embed-bitcode=no",
    "-C", "debuginfo=0",
    "-C", "overflow-checks=no",
    "-C", "inline-threshold=1000",
]

[profile.release]
opt-level = 3
lto = "fat"
codegen-units = 1
panic = "abort"
overflow-checks = false
debug = false
debug-assertions = false
rpath = false
strip = true

[profile.release-with-debug]
inherits = "release"
debug = true
strip = false

[target.x86_64-unknown-linux-gnu]
linker = "clang"
rustflags = [
    "-C", "link-arg=-fuse-ld=lld",
    "-C", "link-arg=-Wl,--gc-sections",
    "-C", "link-arg=-Wl,--icf=all",
    "-C", "target-feature=+sse4.2,+avx,+avx2,+fma,+bmi1,+bmi2,+lzcnt,+popcnt",
]

[target.x86_64-apple-darwin]
rustflags = [
    "-C", "target-feature=+sse4.2,+avx,+avx2,+fma,+bmi1,+bmi2,+lzcnt,+popcnt",
]

[target.x86_64-pc-windows-msvc]
rustflags = [
    "-C", "target-feature=+sse4.2,+avx,+avx2,+fma,+bmi1,+bmi2,+lzcnt,+popcnt",
]
"#.to_string()
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn test_compiler_optimizer_creation() {
        let optimizer = CompilerOptimizer::new();
        assert!(optimizer.optimization_flags.enable_lto);
        assert_eq!(optimizer.optimization_flags.opt_level as u8, OptLevel::Aggressive as u8);
    }
    
    #[test]
    fn test_compile_time_processor() {
        const PROCESSOR: CompileTimeOptimizedEventProcessor = CompileTimeOptimizedEventProcessor::new();
        
        let route = PROCESSOR.route_event_zero_cost(42);
        assert!(route < 16); // 应该路由到16个工作线程之一
        
        let hash = PROCESSOR.hash_lookup_optimized(100);
        assert!(hash > 0); // 哈希值应该非零
    }
    
    #[test]
    fn test_ultra_performance_config() {
        let flags = OptimizationFlags::ultra_performance();
        assert!(flags.enable_lto);
        assert_eq!(flags.target_cpu, "native");
        assert!(!flags.target_features.is_empty());
        
        let codegen = CodegenConfig::ultra_performance();
        assert!(codegen.panic_abort);
        assert!(!codegen.overflow_checks);
        assert!(codegen.enable_simd);
    }
    
    #[test] 
    fn test_compiler_config_generation() {
        let optimizer = CompilerOptimizer::new();
        let config = optimizer.generate_ultra_performance_config().unwrap();
        
        assert!(!config.rustflags.is_empty());
        assert!(config.rustflags.contains(&"-C".to_string()));
        assert!(config.rustflags.contains(&"opt-level=3".to_string()));
        
        assert!(config.env_vars.contains_key("CARGO_INCREMENTAL"));
    }
    
    #[test]
    fn test_simd_compile_time_optimization() {
        #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
        if is_x86_feature_detected!("avx2") {
            let data = vec![1u64, 2, 3, 4, 5, 6, 7, 8];
            let sum = unsafe { SIMDCompileTimeOptimizer::vectorized_sum_compile_time(&data) };
            assert_eq!(sum, 36); // 1+2+3+4+5+6+7+8 = 36
        }

        #[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
        {
            let data = vec![1u64, 2, 3, 4, 5, 6, 7, 8];
            let sum = SIMDCompileTimeOptimizer::vectorized_sum_compile_time(&data);
            assert_eq!(sum, 36); // 1+2+3+4+5+6+7+8 = 36
        }
    }
    
    #[test]
    fn test_build_script_generation() {
        let build_script = generate_build_script();
        assert!(build_script.contains("avx2"));
        assert!(build_script.contains("TARGET_FEATURE"));
        assert!(build_script.contains("lld"));
    }
    
    #[test]
    fn test_cargo_config_generation() {
        let config = generate_cargo_config_toml();
        assert!(config.contains("opt-level = 3"));
        assert!(config.contains("lto = \"fat\""));
        assert!(config.contains("target-cpu=native"));
        assert!(config.contains("panic = \"abort\""));
    }
}