use anyhow::Result;
use scopeguard::defer;
use serde::Serialize;
use smartstring::alias::String;
use std::{
    fmt,
    hash::{DefaultHasher, Hash as _, Hasher as _},
    sync::LazyLock,
    sync::atomic::{AtomicBool, Ordering},
};
use tauri_plugin_shell::ShellExt as _;
use tokio::fs;

use crate::config::Config;
use crate::core::handle;
use crate::singleton;
use crate::utils::{dirs, help};
use clash_verge_logging::{Type, logging};

const SYNTAX_CHECK_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(5);

static LAST_VALIDATED: LazyLock<parking_lot::Mutex<Option<u64>>> = LazyLock::new(|| parking_lot::Mutex::new(None));

async fn validation_fingerprint(yaml: &str) -> u64 {
    let core = Config::verge().await.latest_arc().get_valid_clash_core();
    let mut hasher = DefaultHasher::new();
    yaml.hash(&mut hasher);
    core.as_str().hash(&mut hasher);
    let binary = std::env::current_exe()
        .into_iter()
        .map(|exe| exe.with_file_name(format!("{}{}", core.as_str(), std::env::consts::EXE_SUFFIX)));
    // The test run reads geo databases from the app dir; a geo update must revalidate.
    let geo = dirs::app_home_dir().into_iter().flat_map(|dir| {
        super::runtime_bundle::GEO_ASSETS
            .iter()
            .map(move |asset| dir.join(asset))
    });
    for path in binary.chain(geo) {
        match std::fs::metadata(&path) {
            Ok(meta) => {
                meta.len().hash(&mut hasher);
                meta.modified().ok().hash(&mut hasher);
            }
            Err(_) => 0u8.hash(&mut hasher),
        }
    }
    hasher.finish()
}

pub struct CoreConfigValidator {
    is_processing: AtomicBool,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
#[serde(rename_all = "camelCase")]
pub enum ValidationErrorKind {
    FileMissing,
    FileRead,
    YamlSyntax,
    YamlMapping,
    ScriptSyntax,
    ScriptMissingMain,
    CoreRejected,
    ProcessTerminated,
    Timeout,
}

impl ValidationErrorKind {
    pub fn from_message(message: &str) -> Self {
        let lower = message.to_ascii_lowercase();

        if lower.contains("file not found") {
            Self::FileMissing
        } else if lower.contains("failed to read") || lower.contains("无法读取") {
            Self::FileRead
        } else if lower.contains("script must contain a main function") {
            Self::ScriptMissingMain
        } else if lower.contains("script syntax error") {
            Self::ScriptSyntax
        } else if lower.contains("mapping values are not allowed")
            || lower.contains("failed to transform to yaml mapping")
            || lower.contains("failed to apply merge")
        {
            Self::YamlMapping
        } else if lower.contains("yaml syntax error") || lower.contains("did not find expected key") {
            Self::YamlSyntax
        } else if lower.contains("timeout") || lower.contains("超时") {
            Self::Timeout
        } else if lower.contains("terminated") || lower.contains("被终止") {
            Self::ProcessTerminated
        } else {
            Self::CoreRejected
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
#[serde(rename_all = "camelCase")]
pub enum ValidationSkipReason {
    Exiting,
    Debounced,
}

impl fmt::Display for ValidationSkipReason {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Exiting => write!(f, "application is exiting"),
            Self::Debounced => write!(f, "debounced"),
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
#[serde(tag = "status", rename_all = "camelCase")]
pub enum ValidationOutcome {
    Valid,
    Invalid { kind: ValidationErrorKind, message: String },
    Skipped { reason: ValidationSkipReason },
    Busy,
}

impl ValidationOutcome {
    pub fn invalid(kind: ValidationErrorKind, message: impl Into<String>) -> Self {
        Self::Invalid {
            kind,
            message: message.into(),
        }
    }

    pub fn invalid_from_message(message: impl Into<String>) -> Self {
        let message = message.into();
        Self::invalid(ValidationErrorKind::from_message(&message), message)
    }

    pub const fn is_valid(&self) -> bool {
        matches!(self, Self::Valid)
    }
}

impl fmt::Display for ValidationOutcome {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Valid => write!(f, "configuration is valid"),
            Self::Invalid { message, .. } => write!(f, "{message}"),
            Self::Skipped { reason } => write!(f, "Configuration validation skipped: {reason}"),
            Self::Busy => write!(f, "Configuration validation is already running"),
        }
    }
}

impl CoreConfigValidator {
    pub const fn new() -> Self {
        Self {
            is_processing: AtomicBool::new(false),
        }
    }

    pub fn try_start(&self) -> bool {
        !self.is_processing.swap(true, Ordering::AcqRel)
    }

    pub fn finish(&self) {
        self.is_processing.store(false, Ordering::Release)
    }
}

impl CoreConfigValidator {
    async fn is_script_file(path: &str) -> Result<bool> {
        if has_ext(path, "yaml") || has_ext(path, "yml") {
            return Ok(false);
        } else if has_ext(path, "js") {
            return Ok(true);
        }

        let content = match fs::read_to_string(path).await {
            Ok(content) => content,
            Err(err) => {
                logging!(warn, Type::Validate, "无法读取文件以检测类型: {}, 错误: {}", path, err);
                return Err(anyhow::anyhow!("Failed to read file to detect type: {}", err));
            }
        };

        let has_yaml_features = content.contains(": ")
            || content.contains("#")
            || content.contains("---")
            || content.lines().any(|line| line.trim().starts_with("- "));

        let has_js_features = content.contains("function ")
            || content.contains("const ")
            || content.contains("let ")
            || content.contains("var ")
            || content.contains("//")
            || content.contains("/*")
            || content.contains("*/")
            || content.contains("export ")
            || content.contains("import ");

        if has_yaml_features && !has_js_features {
            return Ok(false);
        } else if has_js_features && !has_yaml_features {
            return Ok(true);
        } else if has_yaml_features && has_js_features {
            if content.contains("function main")
                || content.contains("module.exports")
                || content.contains("export default")
            {
                return Ok(true);
            }

            let yaml_pattern_count = content.lines().filter(|line| line.contains(": ")).count();

            if yaml_pattern_count > 2 {
                return Ok(false);
            }
        }

        // Unknown files take the safer YAML validation path.
        logging!(debug, Type::Validate, "无法确定文件类型，默认当作YAML处理: {}", path);
        Ok(false)
    }

    async fn validate_file_syntax_outcome(config_path: &str) -> Result<ValidationOutcome> {
        logging!(info, Type::Validate, "开始检查文件: {}", config_path);

        let content = match fs::read_to_string(config_path).await {
            Ok(content) => content,
            Err(err) => {
                let error_msg: String = format!("Failed to read file: {err}").into();
                logging!(error, Type::Validate, "Failed to read file {config_path}: {err}");
                return Ok(ValidationOutcome::invalid_from_message(error_msg));
            }
        };
        logging!(info, Type::Validate, "进行YAML语法检查");
        match serde_yaml_ng::from_str::<serde_yaml_ng::Value>(&content) {
            Ok(_) => {
                logging!(info, Type::Validate, "YAML语法检查通过");
                Ok(ValidationOutcome::Valid)
            }
            Err(err) => {
                let error_msg: String = format!("YAML syntax error: {err}").into();
                logging!(error, Type::Validate, "YAML syntax error in {config_path}: {err}");
                Ok(ValidationOutcome::invalid_from_message(error_msg))
            }
        }
    }

    async fn validate_script_file_outcome(path: &str) -> Result<ValidationOutcome> {
        let content = match fs::read_to_string(path).await {
            Ok(content) => content,
            Err(err) => {
                let error_msg: String = format!("Failed to read script file: {err}").into();
                logging!(warn, Type::Validate, "Failed to read script file {path}: {err}");
                return Ok(ValidationOutcome::invalid_from_message(error_msg));
            }
        };

        logging!(debug, Type::Validate, "验证脚本文件: {}", path);
        let has_main =
            content.contains("function main") || content.contains("const main") || content.contains("let main");

        // Boa parsing is pure CPU; keep it off the async worker, with a timeout.
        let syntax = crate::process::AsyncHandler::spawn_blocking(move || {
            use boa_engine::{Context, Source};

            let mut context = Context::default();
            let _ = context.eval(Source::from_bytes(
                "var console = Object.freeze({log(...data){},info(...data){},error(...data){},debug(...data){}});",
            ));
            context
                .eval(Source::from_bytes(&content))
                .map(|_| ())
                .map_err(|err| err.to_string())
        });
        let result = match tokio::time::timeout(SYNTAX_CHECK_TIMEOUT, syntax).await {
            Ok(Ok(evaluated)) => evaluated,
            Ok(Err(join_err)) => Err(format!("syntax check task failed: {join_err}")),
            Err(_) => Err("syntax check timed out".to_owned()),
        };

        match result {
            Ok(()) => {
                logging!(debug, Type::Validate, "脚本语法验证通过: {}", path);

                if !has_main {
                    let error_msg = "Script must contain a main function";
                    logging!(warn, Type::Validate, "脚本缺少main函数: {}", path);
                    return Ok(ValidationOutcome::invalid_from_message(error_msg));
                }

                Ok(ValidationOutcome::Valid)
            }
            Err(err) => {
                let error_msg: String = format!("Script syntax error: {err}").into();
                logging!(warn, Type::Validate, "Script syntax error in {path}: {err}");
                Ok(ValidationOutcome::invalid_from_message(error_msg))
            }
        }
    }

    pub async fn validate_config_file_outcome(
        config_path: &str,
        is_merge_file: Option<bool>,
    ) -> Result<ValidationOutcome> {
        if handle::Handle::global().is_exiting() {
            logging!(info, Type::Core, "应用正在退出，跳过验证");
            return Ok(ValidationOutcome::Skipped {
                reason: ValidationSkipReason::Exiting,
            });
        }

        if !std::path::Path::new(config_path).exists() {
            let error_msg: String = format!("File not found: {config_path}").into();
            return Ok(ValidationOutcome::invalid_from_message(error_msg));
        }

        if is_merge_file.unwrap_or(false) {
            logging!(info, Type::Validate, "检测到Merge文件，仅进行语法检查: {}", config_path);
            return Self::validate_file_syntax_outcome(config_path).await;
        }

        let is_script = match Self::is_script_file(config_path).await {
            Ok(result) => result,
            Err(err) => {
                logging!(warn, Type::Validate, "无法确定文件类型: {}, 错误: {}", config_path, err);
                return Self::validate_config_internal_outcome(config_path).await;
            }
        };

        if is_script {
            logging!(
                info,
                Type::Validate,
                "检测到脚本文件，使用JavaScript验证: {}",
                config_path
            );
            return Self::validate_script_file_outcome(config_path).await;
        }

        logging!(info, Type::Validate, "使用Clash内核验证配置文件: {}", config_path);
        Self::validate_config_internal_outcome(config_path).await
    }

    async fn validate_config_internal_outcome(config_path: &str) -> Result<ValidationOutcome> {
        if handle::Handle::global().is_exiting() {
            logging!(info, Type::Validate, "应用正在退出，跳过验证");
            return Ok(ValidationOutcome::Skipped {
                reason: ValidationSkipReason::Exiting,
            });
        }

        logging!(info, Type::Validate, "开始验证配置文件: {}", config_path);

        let clash_core = Config::verge().await.latest_arc().get_valid_clash_core();
        logging!(info, Type::Validate, "使用内核: {}", clash_core);

        let app_handle = handle::Handle::app_handle();
        let app_dir = dirs::app_home_dir()?;
        let app_dir_str = dirs::path_to_str(&app_dir)?;
        logging!(info, Type::Validate, "验证目录: {}", app_dir_str);

        let command = app_handle.shell().sidecar(clash_core.as_str()).map_err(|error| {
            anyhow::anyhow!("failed to build validation command for core {clash_core:?}: {error:#}")
        })?;
        let command = command.args(["-t", "-d", app_dir_str, "-f", config_path]);
        let output = command.output().await.map_err(|error| {
            anyhow::anyhow!(
                "failed to run validation core {clash_core:?} for config {config_path:?} in data directory {}: {error:#}",
                app_dir.display()
            )
        })?;

        let status = &output.status;
        let stderr = &output.stderr;
        let stdout = &output.stdout;

        let error_keywords = ["FATA", "fatal", "Parse config error", "level=fatal"];
        let has_error = !status.success() || contains_any_keyword(stderr, &error_keywords);

        logging!(info, Type::Validate, "-------- 验证结果 --------");

        if !stderr.is_empty() {
            logging!(info, Type::Validate, "stderr输出:\n{:?}", stderr);
        }

        if has_error {
            logging!(info, Type::Validate, "发现错误，开始处理错误信息");
            let error_msg: String = if !stdout.is_empty() {
                str::from_utf8(stdout).unwrap_or_default().into()
            } else if !stderr.is_empty() {
                str::from_utf8(stderr).unwrap_or_default().into()
            } else if let Some(code) = status.code() {
                format!("验证进程异常退出，退出码: {code}").into()
            } else {
                "验证进程被终止，请检查是否有安全软件阻止了内核运行，或电脑 CPU/运行环境是否支持该内核程序。".into()
            };

            logging!(info, Type::Validate, "-------- 验证结束 --------");
            let outcome = if status.code().is_none() {
                ValidationOutcome::invalid(ValidationErrorKind::ProcessTerminated, error_msg)
            } else {
                ValidationOutcome::invalid_from_message(error_msg)
            };
            Ok(outcome)
        } else {
            logging!(info, Type::Validate, "验证成功");
            logging!(info, Type::Validate, "-------- 验证结束 --------");
            Ok(ValidationOutcome::Valid)
        }
    }

    /// Skips the subprocess when these bytes were already accepted by the same core build.
    pub async fn validate_config_outcome_with(&self, yaml: &str) -> Result<ValidationOutcome> {
        if !self.try_start() {
            logging!(info, Type::Validate, "验证已在进行中，跳过新的验证请求");
            return Ok(ValidationOutcome::Busy);
        }
        defer! {
            self.finish();
        }
        logging!(info, Type::Validate, "生成临时配置文件用于验证");

        let fingerprint = validation_fingerprint(yaml).await;
        if *LAST_VALIDATED.lock() == Some(fingerprint) {
            logging!(info, Type::Validate, "配置与上次通过验证的字节一致，跳过内核检查");
            return Ok(ValidationOutcome::Valid);
        }

        let check_path = dirs::app_home_dir()?.join(crate::constants::files::CHECK_CONFIG);
        help::save_yaml_str(&check_path, yaml).await?;
        let outcome = Self::validate_config_internal_outcome(dirs::path_to_str(&check_path)?).await?;
        if outcome.is_valid() {
            *LAST_VALIDATED.lock() = Some(fingerprint);
            let _ = fs::remove_file(&check_path).await;
        }
        Ok(outcome)
    }
}

fn has_ext<P: AsRef<std::path::Path>>(path: P, ext: &str) -> bool {
    path.as_ref()
        .extension()
        .and_then(|s| s.to_str())
        .map(|s| s.eq_ignore_ascii_case(ext))
        .unwrap_or(false)
}

fn contains_any_keyword<'a>(buf: &'a [u8], keywords: &'a [&str]) -> bool {
    for &kw in keywords {
        let needle = kw.as_bytes();
        if needle.is_empty() {
            continue;
        }
        let mut i = 0;
        while i + needle.len() <= buf.len() {
            if &buf[i..i + needle.len()] == needle {
                return true;
            }
            i += 1;
        }
    }
    false
}

singleton!(CoreConfigValidator, CORECONFIGVALIDATOR);