use std::collections::HashMap;
use std::path::PathBuf;
use std::time::Duration;

use crate::core::config::{AppConfig, RegionConfig, RegionProviderConfig};
use crate::core::errors::AssetExecutionError;
use crate::core::export_pipeline::extract_unity_asset_bundle;
use crate::core::regions::{compile_patterns, matches_any};
use crate::core::retry::retry_async;
use aes::cipher::block_padding::Pkcs7;
use aes::cipher::{BlockDecryptMut, KeyIvInit};
use chrono::FixedOffset;
use common::updater::{AssetCategory, DownloadTask, SyncContext};
use reqwest::header::{
    ACCEPT, ACCEPT_ENCODING, ACCEPT_LANGUAGE, CONNECTION, COOKIE, HeaderMap, HeaderValue,
    SET_COOKIE, USER_AGENT,
};
use serde::{Deserialize, Serialize};

type Aes128CbcDec = cbc::Decryptor<aes::Aes128>;
type Aes192CbcDec = cbc::Decryptor<aes::Aes192>;
type Aes256CbcDec = cbc::Decryptor<aes::Aes256>;

/// Deserializes a msgpack/JSON null or missing value as an empty String.
/// Go silently coerces nil → zero value for non-pointer types; this helper
/// mirrors that behavior for String fields.
fn de_null_as_empty_string<'de, D>(deserializer: D) -> Result<String, D::Error>
where
    D: serde::Deserializer<'de>,
{
    Ok(Option::<String>::deserialize(deserializer)?.unwrap_or_default())
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AssetBundleDetail {
    #[serde(rename = "bundleName", deserialize_with = "de_null_as_empty_string")]
    pub bundle_name: String,
    #[serde(rename = "cacheFileName", deserialize_with = "de_null_as_empty_string")]
    pub cache_file_name: String,
    #[serde(
        rename = "cacheDirectoryName",
        deserialize_with = "de_null_as_empty_string"
    )]
    pub cache_directory_name: String,
    // nuverse regions use `crc` instead of `hash`; the server may send nil here.
    #[serde(rename = "hash", deserialize_with = "de_null_as_empty_string")]
    pub hash: String,
    #[serde(rename = "category")]
    pub category: AssetCategory,
    #[serde(rename = "crc")]
    pub crc: i64,
    #[serde(rename = "fileSize")]
    pub file_size: i64,
    #[serde(rename = "dependencies")]
    pub dependencies: Vec<String>,
    #[serde(rename = "paths", default)]
    pub paths: Vec<String>,
    #[serde(rename = "isBuiltin")]
    pub is_builtin: bool,
    #[serde(rename = "isRelocate")]
    pub is_relocate: Option<bool>,
    #[serde(rename = "md5Hash")]
    pub md5_hash: Option<String>,
    #[serde(rename = "downloadPath")]
    pub download_path: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AssetBundleInfo {
    #[serde(rename = "version")]
    pub version: Option<String>,
    #[serde(rename = "os")]
    pub os: Option<String>,
    #[serde(rename = "bundles")]
    pub bundles: HashMap<String, AssetBundleDetail>,
}

#[derive(Debug, Clone)]
pub struct AssetExecutionContext {
    client: reqwest::Client,
    region_name: String,
    region: RegionConfig,
    retry: crate::core::config::RetryConfig,
    runtime_cookie: Option<String>,
    resolved_asset_version: Option<String>,
    pub sync_context: SyncContext,
}

impl AssetExecutionContext {
    pub fn new(
        app_config: &AppConfig,
        sync_context: &SyncContext,
        region: &RegionConfig,
    ) -> Result<Self, AssetExecutionError> {
        let mut headers = HeaderMap::new();
        headers.insert(ACCEPT, HeaderValue::from_static("*/*"));
        headers.insert(
            USER_AGENT,
            HeaderValue::from_static("ProductName/134 CFNetwork/1408.0.4 Darwin/22.5.0"),
        );
        headers.insert(CONNECTION, HeaderValue::from_static("keep-alive"));
        headers.insert(
            ACCEPT_ENCODING,
            HeaderValue::from_static("gzip, deflate, br"),
        );
        headers.insert(
            ACCEPT_LANGUAGE,
            HeaderValue::from_static("zh-CN,zh-Hans;q=0.9"),
        );
        headers.insert(
            "X-Unity-Version",
            HeaderValue::from_str(&region.runtime.unity_version)
                .map_err(|err| AssetExecutionError::HttpClient(err.to_string()))?,
        );

        let mut builder = reqwest::Client::builder()
            .default_headers(headers)
            .connect_timeout(Duration::from_secs(10))
            .timeout(Duration::from_secs(180))
            .pool_max_idle_per_host(100)
            .tcp_keepalive(Duration::from_secs(30));

        if let Some(proxy) = &app_config.execution.proxy
            && !proxy.is_empty()
        {
            builder = builder.proxy(
                reqwest::Proxy::all(proxy)
                    .map_err(|err| AssetExecutionError::HttpClient(err.to_string()))?,
            );
        }

        Ok(Self {
            client: builder
                .build()
                .map_err(|err| AssetExecutionError::HttpClient(err.to_string()))?,
            sync_context: sync_context.clone(),
            region_name: sync_context.region.clone(),
            region: region.clone(),
            retry: app_config.execution.retry.clone(),
            runtime_cookie: None,
            resolved_asset_version: sync_context.asset_version.clone(),
        })
    }

    pub async fn fetch_tasks(&mut self) -> Result<Vec<DownloadTask>, AssetExecutionError> {
        if self.requires_cookies() {
            self.fetch_runtime_cookies().await?;
        }

        let info = self.fetch_asset_bundle_info().await?;

        let tasks = self.build_download_tasks(&info);
        Ok(tasks)
    }

    pub async fn download(
        &self,
        task: &DownloadTask,
        app_config: &AppConfig,
    ) -> Result<(PathBuf, /*single file*/ bool), AssetExecutionError> {
        let ctx = self.clone();
        ctx.download_and_export_bundle(app_config, task).await
    }

    fn requires_cookies(&self) -> bool {
        match &self.region.provider {
            RegionProviderConfig::ColorfulPalette {
                required_cookies, ..
            } => *required_cookies,
            RegionProviderConfig::Nuverse {
                required_cookies, ..
            } => *required_cookies,
        }
    }

    async fn fetch_runtime_cookies(&mut self) -> Result<(), AssetExecutionError> {
        let url = match &self.region.provider {
            RegionProviderConfig::ColorfulPalette {
                cookie_bootstrap_url,
                ..
            }
            | RegionProviderConfig::Nuverse {
                cookie_bootstrap_url,
                ..
            } => cookie_bootstrap_url.clone().unwrap_or_else(|| {
                "https://issue.sekai.colorfulpalette.org/api/signature".to_string()
            }),
        };
        self.runtime_cookie = retry_async(
            &self.retry,
            "cookie bootstrap",
            |_| async {
                let response = self.client.post(&url).send().await?;
                if response.status().is_success() {
                    Ok(response
                        .headers()
                        .get(SET_COOKIE)
                        .and_then(|value| value.to_str().ok())
                        .map(str::to_string))
                } else {
                    Err(AssetExecutionError::HttpStatus {
                        url: url.clone(),
                        status: response.status().as_u16(),
                    })
                }
            },
            is_retryable_http_error,
        )
        .await?;
        Ok(())
    }

    async fn fetch_asset_bundle_info(&mut self) -> Result<AssetBundleInfo, AssetExecutionError> {
        let url = self.render_asset_info_url().await?;
        let body = self.get_with_retry(&url).await?;
        decrypt_asset_bundle_info(
            self.region.crypto.aes_key_hex.as_deref().ok_or_else(|| {
                AssetExecutionError::MissingCryptoConfig {
                    region: self.region_name.clone(),
                }
            })?,
            self.region.crypto.aes_iv_hex.as_deref().ok_or_else(|| {
                AssetExecutionError::MissingCryptoConfig {
                    region: self.region_name.clone(),
                }
            })?,
            &body,
        )
    }

    async fn render_asset_info_url(&mut self) -> Result<String, AssetExecutionError> {
        match &self.region.provider {
            RegionProviderConfig::ColorfulPalette {
                asset_info_url_template,
                profile,
                profile_hashes,
                ..
            } => {
                let asset_version =
                    self.sync_context.asset_version.as_deref().ok_or_else(|| {
                        AssetExecutionError::MissingAssetVersionOrHash {
                            region: self.region_name.clone(),
                        }
                    })?;
                let asset_hash = self.sync_context.asset_hash.as_deref().ok_or_else(|| {
                    AssetExecutionError::MissingAssetVersionOrHash {
                        region: self.region_name.clone(),
                    }
                })?;
                let profile_hash = profile_hashes.get(profile).ok_or_else(|| {
                    AssetExecutionError::MissingProfileHash {
                        region: self.region_name.clone(),
                        profile: profile.clone(),
                    }
                })?;
                Ok(asset_info_url_template
                    .replace("{env}", profile)
                    .replace("{hash}", profile_hash)
                    .replace("{asset_version}", asset_version)
                    .replace("{asset_hash}", asset_hash)
                    + &time_arg_jst())
            }
            RegionProviderConfig::Nuverse {
                asset_version_url,
                asset_info_url_template,
                ..
            } => {
                // For nuverse, always fetch the version from asset_version_url.
                // The incoming request.asset_version is intentionally ignored here
                // to match Go reference behavior.
                let app_version = self.sync_context.app_version.as_ref().ok_or_else(|| {
                    AssetExecutionError::MissingAppVersion {
                        region: self.region_name.clone(),
                    }
                })?;
                let version_url = asset_version_url.replace("{app_version}", app_version);
                let resolved_version =
                    String::from_utf8_lossy(&self.get_with_retry(&version_url).await?)
                        .trim()
                        .to_string();
                self.resolved_asset_version = Some(resolved_version.clone());
                Ok(asset_info_url_template
                    .replace("{app_version}", app_version)
                    .replace("{asset_version}", &resolved_version)
                    + &time_arg_jst())
            }
        }
    }

    fn render_bundle_url(&self, task: &DownloadTask) -> Result<String, AssetExecutionError> {
        match &self.region.provider {
            RegionProviderConfig::ColorfulPalette {
                asset_bundle_url_template,
                profile,
                profile_hashes,
                ..
            } => {
                let asset_version =
                    self.sync_context.asset_version.as_deref().ok_or_else(|| {
                        AssetExecutionError::MissingAssetVersionOrHash {
                            region: self.region_name.clone(),
                        }
                    })?;
                let asset_hash = self.sync_context.asset_hash.as_deref().ok_or_else(|| {
                    AssetExecutionError::MissingAssetVersionOrHash {
                        region: self.region_name.clone(),
                    }
                })?;
                let profile_hash = profile_hashes.get(profile).ok_or_else(|| {
                    AssetExecutionError::MissingProfileHash {
                        region: self.region_name.clone(),
                        profile: profile.clone(),
                    }
                })?;

                Ok(asset_bundle_url_template
                    .replace("{bundle_path}", &task.download_path)
                    .replace("{asset_version}", asset_version)
                    .replace("{asset_hash}", asset_hash)
                    .replace("{env}", profile)
                    .replace("{hash}", profile_hash)
                    + &time_arg_jst())
            }
            RegionProviderConfig::Nuverse {
                asset_bundle_url_template,
                ..
            } => {
                let app_version = self.sync_context.app_version.as_ref().ok_or_else(|| {
                    AssetExecutionError::MissingAppVersion {
                        region: self.region_name.clone(),
                    }
                })?;
                let asset_version = self
                    .resolved_asset_version
                    .as_deref()
                    .unwrap_or("<resolved-asset-version>");
                Ok(asset_bundle_url_template
                    .replace("{bundle_path}", &task.download_path)
                    .replace("{app_version}", app_version)
                    .replace("{asset_version}", asset_version)
                    + &time_arg_jst())
            }
        }
    }

    async fn get_with_retry(&self, url: &str) -> Result<Vec<u8>, AssetExecutionError> {
        retry_async(
            &self.retry,
            "http get",
            |_| async {
                let mut request = self.client.get(url);
                if let Some(cookie) = &self.runtime_cookie {
                    request = request.header(COOKIE, cookie);
                }
                match request.send().await {
                    Ok(response) if response.status().is_success() => {
                        Ok(response.bytes().await?.to_vec())
                    }
                    Ok(response) => Err(AssetExecutionError::HttpStatus {
                        url: url.to_string(),
                        status: response.status().as_u16(),
                    }),
                    Err(err) => Err(AssetExecutionError::Http(err)),
                }
            },
            is_retryable_http_error,
        )
        .await
    }

    fn build_download_tasks(&self, info: &AssetBundleInfo) -> Vec<DownloadTask> {
        let skip_patterns = compile_patterns(&self.sync_context.filters.skip);
        let start_app_patterns = compile_patterns(&self.sync_context.filters.start_app);
        let on_demand_patterns = compile_patterns(&self.sync_context.filters.on_demand);
        let mut tasks = Vec::new();

        for (bundle_name, detail) in &info.bundles {
            if matches_any(&skip_patterns, bundle_name) {
                continue;
            }
            let category_patterns = match &detail.category {
                AssetCategory::StartApp => &start_app_patterns,
                AssetCategory::OnDemand => &on_demand_patterns,
                AssetCategory::Other(_) => continue,
            };
            if category_patterns.is_empty() || !matches_any(category_patterns, bundle_name) {
                continue;
            }

            let bundle_hash = match self.region.provider {
                RegionProviderConfig::Nuverse { .. } => detail.crc.to_string(),
                RegionProviderConfig::ColorfulPalette { .. } => detail.hash.clone(),
            };

            tasks.push(DownloadTask {
                download_path: download_path_for_region(&self.region.provider, bundle_name, detail),
                bundle_path: bundle_name.clone(),
                bundle_hash,
                category: detail.category.clone(),
            });
        }

        tasks.sort_by(|a, b| a.bundle_path.cmp(&b.bundle_path));
        tasks
    }

    async fn download_and_export_bundle(
        &self,
        app_config: &AppConfig,
        task: &DownloadTask,
    ) -> Result<(PathBuf, bool), AssetExecutionError> {
        let bundle_url = self.render_bundle_url(task)?;
        let body = self.get_with_retry(&bundle_url).await?;
        let deobfuscated = deobfuscate(&body);

        let temp_file = std::env::temp_dir()
            .join("sekai-updater")
            .join("obf")
            .join(&self.region_name)
            .join(&task.bundle_path);
        if let Some(parent) = temp_file.parent() {
            std::fs::create_dir_all(parent).map_err(|source| {
                AssetExecutionError::CreateTempDir {
                    path: parent.to_path_buf(),
                    source,
                }
            })?;
        }
        std::fs::write(&temp_file, deobfuscated).map_err(|source| {
            AssetExecutionError::WriteTempFile {
                path: temp_file.clone(),
                source,
            }
        })?;
        let category = match task.category {
            AssetCategory::StartApp => "StartApp",
            AssetCategory::OnDemand => "OnDemand",
            AssetCategory::Other(_) => "OnDemand",
        };
        let export_result = extract_unity_asset_bundle(
            app_config,
            &self.sync_context,
            &self.region,
            &temp_file,
            &task.bundle_path,
            &task.download_path,
            category,
        )
        .await;
        let _ = std::fs::remove_file(&temp_file);
        export_result.map_err(Into::into)
    }
}

pub async fn fetch_live_asset_bundle_info(
    app_config: &AppConfig,
    sync_context: &SyncContext,
    region: &RegionConfig,
) -> Result<AssetBundleInfo, AssetExecutionError> {
    let mut context = AssetExecutionContext::new(app_config, sync_context, region)?;
    if context.requires_cookies() {
        context.fetch_runtime_cookies().await?;
    }
    context.fetch_asset_bundle_info().await
}

fn is_retryable_http_error(err: &AssetExecutionError) -> bool {
    match err {
        AssetExecutionError::Http(_) => true,
        AssetExecutionError::HttpStatus { status, .. } => *status >= 500,
        _ => false,
    }
}

pub fn decrypt_asset_bundle_info(
    aes_key_hex: &str,
    aes_iv_hex: &str,
    content: &[u8],
) -> Result<AssetBundleInfo, AssetExecutionError> {
    if content.is_empty() {
        return Err(AssetExecutionError::EmptyEncryptedContent);
    }
    if !content.len().is_multiple_of(16) {
        return Err(AssetExecutionError::InvalidEncryptedBlockSize);
    }

    let key = hex::decode(aes_key_hex)
        .map_err(|err| AssetExecutionError::InvalidAesKeyHex(err.to_string()))?;
    let iv = hex::decode(aes_iv_hex)
        .map_err(|err| AssetExecutionError::InvalidAesIvHex(err.to_string()))?;
    if iv.len() != 16 {
        return Err(AssetExecutionError::InvalidAesIvLength { got: iv.len() });
    }

    let mut buf = content.to_vec();
    let decrypted = match key.len() {
        16 => Aes128CbcDec::new_from_slices(&key, &iv)
            .map_err(|err| AssetExecutionError::AssetInfoDecode(err.to_string()))?
            .decrypt_padded_mut::<Pkcs7>(&mut buf)
            .map_err(|err| AssetExecutionError::AssetInfoDecode(err.to_string()))?,
        24 => Aes192CbcDec::new_from_slices(&key, &iv)
            .map_err(|err| AssetExecutionError::AssetInfoDecode(err.to_string()))?
            .decrypt_padded_mut::<Pkcs7>(&mut buf)
            .map_err(|err| AssetExecutionError::AssetInfoDecode(err.to_string()))?,
        32 => Aes256CbcDec::new_from_slices(&key, &iv)
            .map_err(|err| AssetExecutionError::AssetInfoDecode(err.to_string()))?
            .decrypt_padded_mut::<Pkcs7>(&mut buf)
            .map_err(|err| AssetExecutionError::AssetInfoDecode(err.to_string()))?,
        _ => {
            return Err(AssetExecutionError::AssetInfoDecode(format!(
                "unsupported AES key length {}",
                key.len()
            )));
        }
    };

    rmp_serde::from_slice::<AssetBundleInfo>(decrypted)
        .map_err(|err| AssetExecutionError::AssetInfoDecode(err.to_string()))
}

pub fn deobfuscate(data: &[u8]) -> Vec<u8> {
    const SIMPLE: [u8; 4] = [0x20, 0x00, 0x00, 0x00];
    const XOR_HEADER: [u8; 4] = [0x10, 0x00, 0x00, 0x00];

    if data.starts_with(&SIMPLE) {
        return data[4..].to_vec();
    }

    if data.starts_with(&XOR_HEADER) {
        let body = &data[4..];
        if body.len() < 128 {
            return body.to_vec();
        }

        let mut header = vec![0u8; 128];
        let pattern = [0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x00];
        for idx in 0..128 {
            header[idx] = body[idx] ^ pattern[idx % pattern.len()];
        }
        let mut output = header;
        output.extend_from_slice(&body[128..]);
        return output;
    }

    data.to_vec()
}

pub fn should_download_bundle(
    sync_context: &SyncContext,
    bundle_name: &str,
    category: &AssetCategory,
) -> bool {
    let compiled = match category {
        AssetCategory::StartApp => compile_patterns(&sync_context.filters.start_app),
        AssetCategory::OnDemand => compile_patterns(&sync_context.filters.on_demand),
        AssetCategory::Other(_) => return false,
    };
    if compiled.is_empty() {
        return false;
    }
    matches_any(&compiled, bundle_name)
}

fn download_path_for_region(
    provider: &RegionProviderConfig,
    bundle_name: &str,
    detail: &AssetBundleDetail,
) -> String {
    match provider {
        RegionProviderConfig::ColorfulPalette { .. } => bundle_name.to_string(),
        RegionProviderConfig::Nuverse { .. } => detail
            .download_path
            .as_ref()
            .map(|prefix| format!("{prefix}/{bundle_name}"))
            .unwrap_or_else(|| bundle_name.to_string()),
    }
}

fn time_arg_jst() -> String {
    let tz = FixedOffset::east_opt(9 * 3600).unwrap();
    format!(
        "?t={}",
        chrono::Utc::now().with_timezone(&tz).format("%Y%m%d%H%M%S")
    )
}