zv 0.15.0

//! Mirrors management and types for Zig versions
//!
//! This module provides functionality for managing HTTP mirrors that host Zig releases.
//! It supports different mirror layouts (flat and versioned), caching strategies,
//! and automatic failover between mirrors.
//!
//! # Key Components
//!
//! - [`Mirror`]: Represents a single HTTP mirror with its URL and layout
//! - [`MirrorManager`]: Manages a collection of mirrors with caching and loading strategies
//! - [`MirrorsIndex`]: Cached representation of mirrors with TTL support
//! - [`Layout`]: Defines how files are organized on a mirror (flat vs versioned)
//!
//! # Cache Strategies
//!
//! The module supports three caching strategies via [`CacheStrategy`]:
//! - `AlwaysRefresh`: Always fetch fresh mirrors from network
//! - `PreferCache`: Use cache if available, fallback to network
//! - `RespectTtl`: Use cache only if not expired, otherwise refresh
//!
//! # Example Usage
//!
//! ```rust,no_run
//! use std::sync::Arc;
//! use reqwest::Client;
//! use crate::app::network::mirror::MirrorManager;
//! use crate::app::network::CacheStrategy;
//!
//! async fn example() -> Result<(), Box<dyn std::error::Error>> {
//!     let client = Arc::new(Client::new());
//!     let cache_path = "/tmp/mirrors.toml";
//!     
//!     let mut manager = MirrorManager::init_and_load(
//!         cache_path,
//!         CacheStrategy::RespectTtl,
//!         client
//!     ).await?;
//!     
//!     let random_mirror = manager.get_random_mirror().await?;
//!     println!("Using mirror: {}", random_mirror.base_url);
//!     
//!     Ok(())
//! }
//! ```

use std::{
    cmp::Ordering,
    collections::HashMap,
    convert::TryFrom,
    path::{Path, PathBuf},
    time::{Duration, Instant},
};

use super::download::download_file;
use super::{CacheStrategy, TARGET};
use crate::{
    CfgErr, NetErr,
    app::{
        MIRRORS_TTL_DAYS,
        constants::ZIG_COMMUNITY_MIRRORS,
        utils::{ProgressHandle, verify_checksum, zv_agent},
    },
};
use chrono::{DateTime, Utc};
use color_eyre::eyre::Result;
use futures::{StreamExt, stream};
use reqwest::{Client, StatusCode};
use semver::Version;
use serde::{Deserialize, Serialize};
use url::Url;

// ============================================================================
// LAYOUT AND MIRROR TYPES
// ============================================================================

#[derive(Debug, Clone, Copy, Default, Serialize, Deserialize, PartialEq)]
pub enum Layout {
    /// Flat layout: {url}/{tarball}
    Flat,
    /// Versioned layout: {url}/{semver}/{tarball}
    #[default]
    Versioned,
}

impl std::ops::Not for Layout {
    type Output = Self;

    fn not(self) -> Self::Output {
        match self {
            Layout::Flat => Layout::Versioned,
            Layout::Versioned => Layout::Flat,
        }
    }
}

impl From<&str> for Layout {
    fn from(s: &str) -> Self {
        match s {
            "flat" => Layout::Flat,
            "versioned" => Layout::Versioned,
            _ => Layout::default(),
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
/// A HTTP mirror for Zig releases
pub struct Mirror {
    pub base_url: Url,
    pub layout: Layout,
    pub rank: u8,
}

// ============================================================================
// MIRROR IMPLEMENTATION
// ============================================================================

impl Mirror {
    /// Attempt to download both tarball and minisig files using this mirror
    ///
    /// This function will automatically try both layouts (flat and versioned) if the first
    /// attempt fails with HTTP 404. If both layouts fail, it returns the error.
    ///
    /// # Arguments
    ///
    /// * `client` - HTTP client for making requests
    /// * `semver_version` - Version to download
    /// * `zig_tarball` - Name of the tarball file
    /// * `tarball_path` - Path where tarball should be saved
    /// * `minisig_path` - Path where minisig file should be saved
    /// * `expected_shasum` - Optional expected SHA256 checksum for verification
    /// * `expected_size` - Optional expected size of the tarball in bytes
    /// * `progress_handle` - Handle for progress reporting
    ///
    /// # Returns
    ///
    /// `Ok(Layout)` with the layout that was successfully used if download succeeds,
    /// otherwise returns the appropriate `NetErr` with detailed context about the failure.
    pub async fn download(
        &self,
        client: &reqwest::Client,
        semver_version: &semver::Version,
        zig_tarball: &str,
        tarball_path: &Path,
        minisig_path: &Path,
        expected_shasum: Option<&str>,
        expected_size: Option<u64>,
        progress_handle: &ProgressHandle,
    ) -> Result<Layout, NetErr> {
        const TARGET: &str = "zv::network::mirror::download";
        tracing::debug!(target: TARGET, "Starting download with mirror: {} (rank: {})", self.base_url, self.rank);

        // Try download with current layout, fall back to alternate on HTTP 404
        match self
            .try_download_with_layout(
                client,
                semver_version,
                zig_tarball,
                tarball_path,
                minisig_path,
                expected_shasum,
                expected_size,
                progress_handle,
                false,
            )
            .await
        {
            Ok(layout) => Ok(layout),
            Err(net_err) => {
                // If the failure was an HTTP 404, try the alternate layout
                if matches!(net_err, NetErr::HTTP(status) if status.as_u16() == 404) {
                    tracing::info!(target: TARGET,
                                  "Initial layout failed with HTTP 404. Trying alternate layout for mirror {}...",
                                  self.base_url);

                    return self
                        .try_download_with_layout(
                            client,
                            semver_version,
                            zig_tarball,
                            tarball_path,
                            minisig_path,
                            expected_shasum,
                            expected_size,
                            progress_handle,
                            true,
                        )
                        .await;
                }

                // Otherwise propagate the concrete network error
                Err(net_err)
            }
        }
    }

    /// Internal helper to try download with a specific layout
    async fn try_download_with_layout(
        &self,
        client: &reqwest::Client,
        semver_version: &semver::Version,
        zig_tarball: &str,
        tarball_path: &Path,
        minisig_path: &Path,
        expected_shasum: Option<&str>,
        expected_size: Option<u64>,
        progress_handle: &ProgressHandle,
        use_alternate_layout: bool,
    ) -> Result<Layout, NetErr> {
        const TARGET: &str = "zv::network::mirror::try_download_with_layout";

        // Determine which layout to use
        let mirror_for_download = if use_alternate_layout {
            let mut alternate = self.clone();
            alternate.layout = !alternate.layout;
            alternate
        } else {
            self.clone()
        };

        // Get download URLs
        let tarball_url = mirror_for_download.get_download_url(semver_version, zig_tarball);
        let minisig_filename = format!("{}.minisig", zig_tarball);
        let minisig_url = mirror_for_download.get_download_url(semver_version, &minisig_filename);

        tracing::trace!(target: TARGET, "Download URLs configured:");
        tracing::trace!(target: TARGET, "  Tarball: {}", tarball_url);
        tracing::trace!(target: TARGET, "  Minisig:  {}", minisig_url);
        if let Some(size) = expected_size {
            tracing::trace!(target: TARGET, "  Expected size: {} bytes ({:.1} MB)", size, size as f64 / 1_048_576.0);
        } else {
            tracing::trace!(target: TARGET, "  Expected size: unknown");
        }
        if let Some(shasum) = expected_shasum {
            tracing::trace!(target: TARGET, "  Expected checksum: {}", shasum);
        } else {
            tracing::trace!(target: TARGET, "  Expected checksum: unknown");
        }

        // Initialize progress reporting
        let progress_msg = format!(
            "Downloading {} from {}",
            zig_tarball, mirror_for_download.base_url
        );
        match progress_handle.start(&progress_msg).await {
            Ok(()) => {}
            Err(e) => {
                tracing::debug!(target: TARGET, "Failed to start progress reporting: {} - continuing without progress updates", e);
            }
        };

        // Phase 1: Download tarball
        match download_file(
            client,
            &tarball_url,
            tarball_path,
            expected_size.unwrap_or(0),
            progress_handle,
        )
        .await
        {
            Ok(()) => {
                tracing::debug!(target: TARGET, "Proceeding to checksum verification...");
            }
            Err(net_err) => {
                tracing::trace!(target: TARGET, "Tarball download failed from mirror {}: {}", mirror_for_download.base_url, net_err);

                match net_err {
                    crate::NetErr::HTTP(status) => {
                        tracing::trace!(target: TARGET, "HTTP error {} during tarball download - mirror may be experiencing issues", status);
                    }
                    crate::NetErr::Timeout(_) => {
                        tracing::trace!(target: TARGET, "Timeout during tarball download - network or mirror performance issues");
                    }
                    _ => {
                        tracing::trace!(target: TARGET, "Network error during tarball download: {}", net_err);
                    }
                }

                return Err(net_err);
            }
        }

        // Phase 2: Verify checksum (if available)
        if let Some(shasum) = expected_shasum {
            tracing::debug!(target: TARGET, "Verifying tarball integrity");
            match verify_checksum(tarball_path, shasum).await {
                Ok(()) => {
                    tracing::debug!(target: TARGET, "Checksum verification successful");
                }
                Err(e) => {
                    tracing::error!(target: TARGET, "Checksum verification failed for tarball from mirror {}: {}", mirror_for_download.base_url, e);
                    // Clean up the corrupted file
                    if tarball_path.exists() {
                        if let Err(cleanup_err) = tokio::fs::remove_file(tarball_path).await {
                            tracing::warn!(target: TARGET, "Failed to remove corrupted tarball file: {}", cleanup_err);
                        } else {
                            tracing::debug!(target: TARGET, "Removed corrupted tarball file");
                        }
                    }
                    return Err(NetErr::Checksum(e.into()));
                }
            }
        } else {
            tracing::debug!(target: TARGET, "Skipping checksum verification - no expected checksum provided");
        }

        // Phase 3: Download minisig file
        tracing::debug!(target: TARGET, "Downloading signature file from {}", minisig_url);
        match progress_handle
            .update("Downloading signature file...")
            .await
        {
            Ok(()) => {
                tracing::debug!(target: TARGET, "Progress updated for minisig download");
            }
            Err(e) => {
                tracing::warn!(target: TARGET, "Failed to update progress for minisig download: {} - continuing", e);
            }
        }

        // For minisig, we don't have size info, so use 0
        match download_file(client, &minisig_url, minisig_path, 0, progress_handle).await {
            Ok(()) => {
                tracing::debug!(target: TARGET, "Minisig download completed successfully");
            }
            Err(net_err) => {
                tracing::error!(target: TARGET, "Minisig download failed from mirror {}: {}", mirror_for_download.base_url, net_err);

                // Provide context about the failure
                match net_err {
                    NetErr::HTTP(status) => {
                        tracing::error!(target: TARGET, "HTTP error {} during minisig download - signature file may not exist on this mirror", status);
                    }
                    NetErr::Timeout(_) => {
                        tracing::error!(target: TARGET, "Timeout during minisig download - network or mirror performance issues");
                    }
                    _ => {
                        tracing::error!(target: TARGET, "Network error during minisig download: {}", net_err);
                    }
                }

                // Clean up the tarball since we couldn't get the signature
                if tarball_path.exists() {
                    if let Err(cleanup_err) = tokio::fs::remove_file(tarball_path).await {
                        tracing::trace!(target: TARGET, "Failed to remove tarball after minisig failure: {}", cleanup_err);
                    } else {
                        tracing::trace!(target: TARGET, "Cleaned up tarball after minisig download failure");
                    }
                }
                return Err(net_err);
            }
        }

        // Verify both files exist and have reasonable sizes
        let tarball_size = match tokio::fs::metadata(tarball_path).await {
            Ok(metadata) => {
                let size = metadata.len();
                tracing::debug!(target: TARGET, "Final tarball size: {} bytes ({:.1} MB)", size, size as f64 / 1_048_576.0);

                if let Some(expected) = expected_size {
                    if size != expected {
                        tracing::warn!(target: TARGET, "Tarball size {} doesn't match expected size {} - this may indicate an issue", size, expected);
                    }
                } else {
                    tracing::debug!(target: TARGET, "No expected size provided for verification");
                }

                size
            }
            Err(e) => {
                tracing::error!(target: TARGET, "Failed to verify final tarball file: {}", e);
                return Err(NetErr::FileIo(e));
            }
        };

        let minisig_size = match tokio::fs::metadata(minisig_path).await {
            Ok(metadata) => {
                let size = metadata.len();
                tracing::debug!(target: TARGET, "Final minisig size: {} bytes", size);

                if size == 0 {
                    tracing::warn!(target: TARGET, "Minisig file is empty - this may indicate a download issue");
                } else if size > 1024 {
                    tracing::warn!(target: TARGET, "Minisig file is unusually large ({} bytes) - this may indicate an error page was downloaded", size);
                }

                size
            }
            Err(e) => {
                tracing::error!(target: TARGET, "Failed to verify final minisig file: {}", e);
                return Err(NetErr::FileIo(e));
            }
        };

        tracing::debug!(target: TARGET, "Download attempt completed successfully with mirror {} - tarball: {:.1} MB, minisig: {} bytes",
                     self.base_url, tarball_size as f64 / 1_048_576.0, minisig_size);

        Ok(mirror_for_download.layout)
    }

    /// Get the primary download URL based on layout
    pub fn get_download_url(&self, version: &Version, tarball: &str) -> String {
        match self.layout {
            Layout::Flat => format!(
                "{}/{tarball}?source={}",
                self.base_url.to_string().trim_end_matches('/'),
                zv_agent()
            ),
            Layout::Versioned => format!(
                "{}/{}/{}?source={}",
                self.base_url.to_string().trim_end_matches('/'),
                version,
                tarball,
                zv_agent()
            ),
        }
    }

    /// Get the download URL with layout inverted
    pub fn get_alternate_url(&self, version: &Version, tarball: &str) -> String {
        let alternate = Mirror {
            base_url: self.base_url.clone(),
            layout: !self.layout,
            rank: self.rank,
        };
        alternate.get_download_url(version, tarball)
    }
    pub fn promote(&mut self) {
        // Lower rank = better
        if self.rank > 1 {
            self.rank -= 1;
        }
    }

    pub fn demote(&mut self) {
        // Higher rank = worse
        self.rank = self.rank.saturating_add(1);
    }
}

impl TryFrom<&str> for Mirror {
    type Error = url::ParseError;

    fn try_from(input: &str) -> Result<Self, Self::Error> {
        let url_str = if input.starts_with("http://") || input.starts_with("https://") {
            input.to_string()
        } else {
            format!("https://{input}")
        };

        let base_url = Url::parse(&url_str)?;

        // Validate scheme
        match base_url.scheme() {
            "http" | "https" => {}
            _ => return Err(url::ParseError::RelativeUrlWithoutBase),
        }
        let layout = match base_url.as_str() {
            u if u.contains("zig.florent.dev") => Layout::Flat,
            u if u.contains("zig.squirl.dev") => Layout::Flat,
            u if u.contains("zigmirror.meox.dev") => Layout::Flat,
            u if u.contains("zig-mirror.tsimnet.eu") => Layout::Flat,
            u if u.contains("pkg.earth") => Layout::Flat,
            u if u.contains("ziglang.freetls.fastly.net") => Layout::Flat,
            u if u.contains("zig.tilok.dev") => Layout::Flat,
            _ => Layout::Versioned,
        };

        Ok(Mirror {
            layout,
            base_url,
            rank: 1,
        })
    }
}

// ============================================================================
// MIRRORS INDEX (CACHE REPRESENTATION)
// ============================================================================

#[derive(Debug, Clone, Serialize, Deserialize)]
/// Represents the cached mirrors.toml file
pub struct MirrorsIndex {
    /// List of community mirrors
    pub mirrors: Vec<Mirror>,
    /// Timestamp when mirrors were last synced
    pub last_synced: DateTime<Utc>,
}

// ============================================================================
// MIRROR BENCHMARKING
// ============================================================================

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum RankApplyPolicy {
    Overwrite,
    Blend,
}

#[derive(Debug, Clone, Serialize)]
pub struct MirrorBenchmarkResult {
    pub base_url: Url,
    pub old_rank: u8,
    pub old_layout: Layout,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub measured_layout: Option<Layout>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub bytes_read: Option<u64>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub elapsed_ms: Option<u128>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub bytes_per_second: Option<f64>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub error: Option<String>,
}

impl MirrorBenchmarkResult {
    pub fn is_success(&self) -> bool {
        self.bytes_per_second.is_some()
    }
}

#[derive(Debug)]
enum BenchmarkProbeError {
    Http(StatusCode),
    Network(reqwest::Error),
    EmptyBody,
}

impl std::fmt::Display for BenchmarkProbeError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Http(status) => write!(f, "HTTP {}", status),
            Self::Network(err) if err.is_timeout() => write!(f, "request timed out"),
            Self::Network(err) => write!(f, "{err}"),
            Self::EmptyBody => write!(f, "response body was empty"),
        }
    }
}

impl MirrorsIndex {
    /// Create a new index with current timestamp
    pub fn new(mirrors: Vec<Mirror>) -> Self {
        Self {
            mirrors,
            last_synced: Utc::now(),
        }
    }

    /// Check if the cache has expired based on TTL
    pub fn is_expired(&self) -> bool {
        self.last_synced + chrono::Duration::days(*MIRRORS_TTL_DAYS) < Utc::now()
    }

    /// Load mirrors index from disk (PreferCache strategy)
    pub async fn load_from_disk(path: impl AsRef<Path>) -> Result<Self, CfgErr> {
        let content = tokio::fs::read_to_string(path.as_ref())
            .await
            .map_err(|io_err| CfgErr::NotFound(io_err.into()))?;

        toml::from_str::<Self>(&content).map_err(|e| CfgErr::ParseFail(e.into()))
    }

    /// Load mirrors index from disk, failing if expired (RespectTtl strategy)
    #[allow(unused)]
    pub async fn load_from_disk_expire_checked(path: impl AsRef<Path>) -> Result<Self, CfgErr> {
        let index = Self::load_from_disk(path.as_ref()).await?;

        if index.is_expired() {
            return Err(CfgErr::CacheExpired(
                path.as_ref().to_string_lossy().to_string(),
            ));
        }

        Ok(index)
    }

    /// Save mirrors index to disk
    pub async fn save(&self, path: impl AsRef<Path>) -> Result<(), CfgErr> {
        let content = toml::to_string_pretty(self).map_err(CfgErr::SerializeFail)?;

        tokio::fs::write(path, content)
            .await
            .map_err(|io_err| CfgErr::WriteFail(io_err.into(), String::from("mirrors index")))?;

        Ok(())
    }
}

// ============================================================================
// MIRROR MANAGER
// ============================================================================

#[derive(Debug, Clone)]
pub struct MirrorManager {
    /// HTTP client for network requests
    client: Client,
    /// Currently loaded mirrors
    mirrors: Vec<Mirror>,
    /// Cached mirrors index (lazy loaded)
    mirrors_index: Option<MirrorsIndex>,
    /// Path to the mirrors cache file
    cache_path: PathBuf,
}

impl MirrorManager {
    // ============================================================================
    // MIRROR MANAGER - CONSTRUCTION AND INITIALIZATION
    // ============================================================================
    /// Create a new mirror manager (doesn't load mirrors yet)
    pub fn new(cache_path: impl AsRef<Path>) -> Result<Self> {
        Ok(Self {
            client: super::create_client()?,
            mirrors: Vec::with_capacity(7), // 7 mirrors listed as of September 2025
            mirrors_index: None,
            cache_path: cache_path.as_ref().to_path_buf(),
        })
    }

    /// Create manager and immediately load mirrors
    pub async fn init_and_load(
        cache_path: impl AsRef<Path>,
        cache_strategy: CacheStrategy,
    ) -> Result<Self, NetErr> {
        let mut manager = Self::new(cache_path)?;
        manager.load_mirrors(cache_strategy).await?;
        Ok(manager)
    }

    // ============================================================================
    // MIRROR MANAGER - LOADING AND CACHING
    // ============================================================================
    /// Load mirrors (self.mirrors) according to the specified cache strategy
    pub async fn load_mirrors(&mut self, cache_strategy: CacheStrategy) -> Result<(), NetErr> {
        match cache_strategy {
            CacheStrategy::AlwaysRefresh => {
                self.refresh_from_network().await?;
            }
            CacheStrategy::PreferCache => {
                if self.try_load_index_from_cache().await.is_err() {
                    tracing::warn!(target: TARGET, "Failed to load cached mirrors, fetching from network");
                    self.refresh_from_network().await?;
                }
            }
            CacheStrategy::OnlyCache => {
                if self.try_load_index_from_cache().await.is_err() {
                    tracing::warn!(target: TARGET, "mirrors cache not found. OnlyCache strategy... returning EmptyMirrors");
                    return Err(NetErr::EmptyMirrors);
                }
            }
            CacheStrategy::RespectTtl => match self.try_load_index_from_cache().await {
                Ok(()) => {
                    if self.is_cache_expired() {
                        tracing::debug!(target: TARGET, "Mirrors cache expired, refreshing");
                        self.refresh_from_network().await?;
                    } else {
                        tracing::debug!(target: TARGET, "Using cached mirrors");
                        self.apply_cached_mirrors_index();
                    }
                }
                Err(_) => {
                    tracing::debug!(target: TARGET, "No valid cache, fetching from network");
                    self.refresh_from_network().await?;
                }
            },
        }
        Ok(())
    }

    /// Try to load mirrors index from cache
    async fn try_load_index_from_cache(&mut self) -> Result<(), NetErr> {
        let index = MirrorsIndex::load_from_disk(&self.cache_path)
            .await
            .map_err(|err| {
                tracing::debug!(target: TARGET, "Failed to load mirrors cache from disk: {err}");
                NetErr::EmptyMirrors
            })?;

        self.mirrors_index = Some(index);
        Ok(())
    }

    /// Apply cached mirrors to active mirrors list
    fn apply_cached_mirrors_index(&mut self) {
        if let Some(ref index) = self.mirrors_index {
            self.mirrors = index.mirrors.clone();
        }
    }

    /// Refresh mirrors from network and cache them, preserving existing layouts and ranks
    async fn refresh_from_network(&mut self) -> Result<(), NetErr> {
        let fresh_mirrors = self.fetch_network_mirrors().await?;

        // Try to load existing cached mirrors to preserve layouts and ranks
        let merged_mirrors = match MirrorsIndex::load_from_disk(&self.cache_path).await {
            Ok(cached_index) => {
                let cached_mirrors_map: std::collections::HashMap<String, Mirror> = cached_index
                    .mirrors
                    .into_iter()
                    .map(|m| (m.base_url.to_string(), m))
                    .collect();

                let merged: Vec<Mirror> = fresh_mirrors
                    .into_iter()
                    .map(|mut fresh_mirror| {
                        if let Some(cached_mirror) =
                            cached_mirrors_map.get(fresh_mirror.base_url.as_str())
                        {
                            fresh_mirror.layout = cached_mirror.layout;
                            fresh_mirror.rank = cached_mirror.rank;
                        }
                        fresh_mirror
                    })
                    .collect();

                tracing::debug!(target: TARGET, "Merged layouts and ranks from {} cached mirrors into {} fresh mirrors",
                             cached_mirrors_map.len(), merged.len());
                merged
            }
            Err(_) => {
                tracing::debug!(target: TARGET, "No cached mirrors found, using fresh mirrors from network");
                fresh_mirrors
            }
        };

        self.mirrors = merged_mirrors;
        let index = MirrorsIndex::new(self.mirrors.clone());

        // Save to cache (log errors but don't fail)
        if let Err(e) = index.save(&self.cache_path).await {
            tracing::error!(target: TARGET, "Failed to save mirrors cache: {}", e);
        }

        self.mirrors_index = Some(index);
        Ok(())
    }

    /// Fetch mirrors from the network
    async fn fetch_network_mirrors(&self) -> Result<Vec<Mirror>, NetErr> {
        tracing::debug!(target: TARGET, "Fetching mirrors from {}", ZIG_COMMUNITY_MIRRORS);

        let mirrors: Vec<Mirror> = self
            .client
            .get(ZIG_COMMUNITY_MIRRORS)
            .send()
            .await
            .map_err(NetErr::Reqwest)?
            .text()
            .await
            .map_err(NetErr::Reqwest)?
            .lines()
            .filter(|line| !line.trim().is_empty()) // Skip empty lines
            .filter_map(|line| {
                Mirror::try_from(line.trim())
                    .inspect_err(|&e| {
                        tracing::warn!(target: TARGET, "Failed to parse mirror '{}': {}", line, e);
                    })
                    .ok()
            })
            .collect();

        if mirrors.is_empty() {
            tracing::error!(target: TARGET, "No valid mirrors found in response");
            return Err(NetErr::EmptyMirrors);
        }

        tracing::debug!(target: TARGET, "Successfully fetched {} mirrors", mirrors.len());
        Ok(mirrors)
    }
    // ============================================================================
    // MIRROR MANAGER - INTERNAL HELPERS
    // ============================================================================
    /// Ensure mirrors are loaded (no-op if mirrors-index is already loaded)
    async fn ensure_mirrors_loaded(&mut self) -> Result<(), NetErr> {
        if self.mirrors_index.is_none() {
            match MirrorsIndex::load_from_disk(&self.cache_path).await {
                Ok(index) => {
                    self.mirrors_index = Some(index);
                }
                Err(_) => {
                    // No cache exists, fetch from network
                    self.refresh_from_network().await?;
                }
            }
        }

        // Apply mirrors from index if we don't have them loaded
        if self.mirrors.is_empty() {
            self.apply_cached_mirrors_index();
        }

        Ok(())
    }
    /// Check if the cached mirrors have expired
    #[inline]
    fn is_cache_expired(&self) -> bool {
        match &self.mirrors_index {
            Some(index) => index.is_expired(),
            None => true, // No cache loaded means it's "expired"
        }
    }
    // ============================================================================
    // MIRROR MANAGER - PUBLIC API
    // ============================================================================
    /// Get all available mirrors from MirrorManager.mirrors (loading if needed)
    pub async fn all_mirrors_mut(&mut self) -> Result<&mut [Mirror], NetErr> {
        if self.mirrors.is_empty() {
            self.ensure_mirrors_loaded().await?;
        }
        Ok(&mut self.mirrors)
    }
    /// Get a random mirror for load balancing, preferring lower rank
    pub async fn get_random_mirror(&mut self) -> Result<&mut Mirror, NetErr> {
        use rand::Rng;
        let mirrors = self.all_mirrors_mut().await?;
        if mirrors.is_empty() {
            return Err(NetErr::EmptyMirrors);
        }

        // If only one mirror, return it
        if mirrors.len() == 1 {
            return Ok(&mut mirrors[0]);
        }

        // Calculate weights inversely proportional to rank
        // Lower rank = higher weight
        let weights: Vec<f64> = mirrors
            .iter()
            .map(|m| 1.0f64 / m.rank as f64) // Rank 1 = weight 1.0, rank 2 = 0.5, rank 5 = 0.2
            .collect();

        // Simple weighted random selection
        let mut rng = rand::rng();
        let total_weight: f64 = weights.iter().sum();
        let mut random_weight = rng.random::<f64>() * total_weight;

        for (i, &weight) in weights.iter().enumerate() {
            random_weight -= weight;
            if random_weight <= 0.0 {
                return Ok(&mut mirrors[i]);
            }
        }

        // Fallback to first mirror (should not happen with correct weights)
        Ok(&mut mirrors[0])
    }
    /// Sort mirrors by rank and return mutable reference to the sorted mirror list
    pub async fn sort_by_rank(&mut self) -> Result<&mut Vec<Mirror>, NetErr> {
        let mirrors = self.all_mirrors_mut().await?;
        mirrors.sort_by_key(|m| m.rank);
        Ok(&mut self.mirrors)
    }
    /// Save the current mirrors to disk (overwriting existing cache)
    /// If no mirrors are loaded, we return EmptyMirrors error
    pub async fn save_index_to_disk(&mut self) -> Result<(), NetErr> {
        // Ensure we have mirrors loaded
        if self.mirrors.is_empty() {
            tracing::debug!(target: TARGET, "No mirrors loaded, cannot save index to disk");
            Err(NetErr::EmptyMirrors)?;
        }

        // Create a fresh index with current mirrors and timestamp
        let index = MirrorsIndex::new(self.mirrors.clone());

        // Save to disk
        index.save(&self.cache_path).await.map_err(|cfg_err| {
            tracing::error!(target: TARGET, "Failed to save mirrors index to disk: {}", cfg_err);
            NetErr::Other(cfg_err.into())
        })?;

        // Update our cached index
        self.mirrors_index = Some(index);

        tracing::debug!(target: TARGET, "Successfully saved mirrors index to {}", self.cache_path.display());
        Ok(())
    }

    /// Benchmark all loaded mirrors using bounded partial downloads.
    pub async fn benchmark_mirrors(
        &mut self,
        semver_version: &Version,
        zig_tarball: &str,
        sample_size: u64,
        concurrency: usize,
    ) -> Result<Vec<MirrorBenchmarkResult>, NetErr> {
        let mirrors = self.all_mirrors_mut().await?.to_vec();
        if mirrors.is_empty() {
            return Err(NetErr::EmptyMirrors);
        }

        let sample_size = sample_size.max(1);
        let concurrency = concurrency.max(1);
        let client = self.client.clone();
        let semver_version = semver_version.clone();
        let zig_tarball = zig_tarball.to_string();

        let mut results = stream::iter(mirrors.into_iter().map(|mirror| {
            let client = client.clone();
            let semver_version = semver_version.clone();
            let zig_tarball = zig_tarball.clone();
            async move {
                benchmark_single_mirror(client, mirror, semver_version, zig_tarball, sample_size)
                    .await
            }
        }))
        .buffer_unordered(concurrency)
        .collect::<Vec<_>>()
        .await;

        results.sort_by(|a, b| {
            benchmark_result_sort_key(a, b)
                .then_with(|| a.base_url.as_str().cmp(b.base_url.as_str()))
        });

        Ok(results)
    }

    /// Apply benchmark results to in-memory mirrors and persist the updated mirror cache.
    pub async fn apply_benchmark_results(
        &mut self,
        results: &[MirrorBenchmarkResult],
        policy: RankApplyPolicy,
    ) -> Result<(), NetErr> {
        self.all_mirrors_mut().await?;

        let ordered = ordered_benchmark_results(results, policy);
        let rank_by_url: HashMap<String, u8> = ordered
            .iter()
            .enumerate()
            .map(|(idx, result)| (result.base_url.to_string(), rank_for_index(idx)))
            .collect();
        let layout_by_url: HashMap<String, Layout> = results
            .iter()
            .filter_map(|result| {
                result
                    .measured_layout
                    .map(|layout| (result.base_url.to_string(), layout))
            })
            .collect();

        for mirror in &mut self.mirrors {
            if let Some(rank) = rank_by_url.get(mirror.base_url.as_str()) {
                mirror.rank = *rank;
            }
            if let Some(layout) = layout_by_url.get(mirror.base_url.as_str()) {
                mirror.layout = *layout;
            }
        }

        self.mirrors.sort_by(|a, b| {
            a.rank
                .cmp(&b.rank)
                .then_with(|| a.base_url.cmp(&b.base_url))
        });
        self.save_index_to_disk().await
    }
}

async fn benchmark_single_mirror(
    client: Client,
    mirror: Mirror,
    semver_version: Version,
    zig_tarball: String,
    sample_size: u64,
) -> MirrorBenchmarkResult {
    let old_rank = mirror.rank;
    let old_layout = mirror.layout;

    match probe_mirror_layout(&client, &mirror, &semver_version, &zig_tarball, sample_size).await {
        Ok(measurement) => benchmark_success(mirror.base_url, old_rank, old_layout, measurement),
        Err(BenchmarkProbeError::Http(status)) if status.as_u16() == 404 => {
            let mut alternate = mirror.clone();
            alternate.layout = !alternate.layout;
            match probe_mirror_layout(
                &client,
                &alternate,
                &semver_version,
                &zig_tarball,
                sample_size,
            )
            .await
            {
                Ok(measurement) => {
                    benchmark_success(mirror.base_url, old_rank, old_layout, measurement)
                }
                Err(err) => benchmark_failure(mirror.base_url, old_rank, old_layout, err),
            }
        }
        Err(err) => benchmark_failure(mirror.base_url, old_rank, old_layout, err),
    }
}

struct BenchmarkMeasurement {
    layout: Layout,
    bytes_read: u64,
    elapsed: Duration,
}

async fn probe_mirror_layout(
    client: &Client,
    mirror: &Mirror,
    semver_version: &Version,
    zig_tarball: &str,
    sample_size: u64,
) -> Result<BenchmarkMeasurement, BenchmarkProbeError> {
    let url = mirror.get_download_url(semver_version, zig_tarball);
    let range_end = sample_size.saturating_sub(1);
    let start = Instant::now();
    let response = client
        .get(url)
        .header(reqwest::header::RANGE, format!("bytes=0-{range_end}"))
        .timeout(Duration::from_secs(15))
        .send()
        .await
        .map_err(BenchmarkProbeError::Network)?;

    match response.status() {
        StatusCode::OK | StatusCode::PARTIAL_CONTENT => {}
        status => return Err(BenchmarkProbeError::Http(status)),
    }

    let mut stream = response.bytes_stream();
    let mut bytes_read = 0u64;

    while let Some(chunk) = stream.next().await {
        let chunk = chunk.map_err(BenchmarkProbeError::Network)?;
        let remaining = sample_size.saturating_sub(bytes_read);
        if remaining == 0 {
            break;
        }
        bytes_read += (chunk.len() as u64).min(remaining);
        if bytes_read >= sample_size {
            break;
        }
    }

    if bytes_read == 0 {
        return Err(BenchmarkProbeError::EmptyBody);
    }

    Ok(BenchmarkMeasurement {
        layout: mirror.layout,
        bytes_read,
        elapsed: start.elapsed(),
    })
}

fn benchmark_success(
    base_url: Url,
    old_rank: u8,
    old_layout: Layout,
    measurement: BenchmarkMeasurement,
) -> MirrorBenchmarkResult {
    let elapsed_secs = measurement.elapsed.as_secs_f64().max(0.001);
    MirrorBenchmarkResult {
        base_url,
        old_rank,
        old_layout,
        measured_layout: Some(measurement.layout),
        bytes_read: Some(measurement.bytes_read),
        elapsed_ms: Some(measurement.elapsed.as_millis()),
        bytes_per_second: Some(measurement.bytes_read as f64 / elapsed_secs),
        error: None,
    }
}

fn benchmark_failure(
    base_url: Url,
    old_rank: u8,
    old_layout: Layout,
    err: BenchmarkProbeError,
) -> MirrorBenchmarkResult {
    MirrorBenchmarkResult {
        base_url,
        old_rank,
        old_layout,
        measured_layout: None,
        bytes_read: None,
        elapsed_ms: None,
        bytes_per_second: None,
        error: Some(err.to_string()),
    }
}

fn benchmark_result_sort_key(a: &MirrorBenchmarkResult, b: &MirrorBenchmarkResult) -> Ordering {
    match (a.bytes_per_second, b.bytes_per_second) {
        (Some(a_bps), Some(b_bps)) => b_bps.partial_cmp(&a_bps).unwrap_or(Ordering::Equal),
        (Some(_), None) => Ordering::Less,
        (None, Some(_)) => Ordering::Greater,
        (None, None) => a.old_rank.cmp(&b.old_rank),
    }
}

fn ordered_benchmark_results(
    results: &[MirrorBenchmarkResult],
    policy: RankApplyPolicy,
) -> Vec<&MirrorBenchmarkResult> {
    match policy {
        RankApplyPolicy::Overwrite => {
            let mut ordered = results.iter().collect::<Vec<_>>();
            ordered.sort_by(|a, b| {
                benchmark_result_sort_key(a, b)
                    .then_with(|| a.base_url.as_str().cmp(b.base_url.as_str()))
            });
            ordered
        }
        RankApplyPolicy::Blend => {
            let mut successes = results
                .iter()
                .filter(|result| result.is_success())
                .collect::<Vec<_>>();
            successes.sort_by(|a, b| {
                benchmark_result_sort_key(a, b)
                    .then_with(|| a.base_url.as_str().cmp(b.base_url.as_str()))
            });

            let speed_rank_by_url: HashMap<String, usize> = successes
                .iter()
                .enumerate()
                .map(|(idx, result)| (result.base_url.to_string(), idx + 1))
                .collect();

            let mut failures = results
                .iter()
                .filter(|result| !result.is_success())
                .collect::<Vec<_>>();
            failures.sort_by(|a, b| {
                a.old_rank
                    .cmp(&b.old_rank)
                    .then_with(|| a.base_url.as_str().cmp(b.base_url.as_str()))
            });

            successes.sort_by(|a, b| {
                let a_speed_rank = speed_rank_by_url
                    .get(a.base_url.as_str())
                    .copied()
                    .unwrap_or(usize::MAX);
                let b_speed_rank = speed_rank_by_url
                    .get(b.base_url.as_str())
                    .copied()
                    .unwrap_or(usize::MAX);
                let a_score = a.old_rank as f64 + a_speed_rank as f64;
                let b_score = b.old_rank as f64 + b_speed_rank as f64;
                a_score
                    .partial_cmp(&b_score)
                    .unwrap_or(Ordering::Equal)
                    .then_with(|| a.base_url.as_str().cmp(b.base_url.as_str()))
            });

            successes.extend(failures);
            successes
        }
    }
}

fn rank_for_index(idx: usize) -> u8 {
    u8::try_from(idx + 1).unwrap_or(u8::MAX)
}

#[cfg(test)]
mod tests {
    use super::*;
    use chrono::Utc;
    use tempfile::tempdir;
    use wiremock::{
        Mock, MockServer, ResponseTemplate,
        matchers::{header, method, path},
    };

    fn test_mirror(url: &str, rank: u8) -> Mirror {
        Mirror {
            base_url: Url::parse(url).unwrap(),
            layout: Layout::Flat,
            rank,
        }
    }

    fn benchmark_result(
        url: &str,
        old_rank: u8,
        bytes_per_second: Option<f64>,
    ) -> MirrorBenchmarkResult {
        MirrorBenchmarkResult {
            base_url: Url::parse(url).unwrap(),
            old_rank,
            old_layout: Layout::Flat,
            measured_layout: bytes_per_second.map(|_| Layout::Flat),
            bytes_read: bytes_per_second.map(|_| 1024),
            elapsed_ms: bytes_per_second.map(|_| 10),
            bytes_per_second,
            error: if bytes_per_second.is_some() {
                None
            } else {
                Some("failed".to_string())
            },
        }
    }

    #[tokio::test]
    async fn overwrite_policy_sets_speed_order_and_places_failures_last() {
        let dir = tempdir().unwrap();
        let cache_path = dir.path().join("mirrors.toml");
        let mut manager = MirrorManager::new(&cache_path).unwrap();
        manager.mirrors = vec![
            test_mirror("https://slow.example", 1),
            test_mirror("https://fast.example", 5),
            test_mirror("https://failed.example", 2),
        ];
        manager.mirrors_index = Some(MirrorsIndex {
            mirrors: manager.mirrors.clone(),
            last_synced: Utc::now(),
        });

        let results = vec![
            benchmark_result("https://slow.example/", 1, Some(10.0)),
            benchmark_result("https://fast.example/", 5, Some(100.0)),
            benchmark_result("https://failed.example/", 2, None),
        ];

        manager
            .apply_benchmark_results(&results, RankApplyPolicy::Overwrite)
            .await
            .unwrap();

        let ranks = manager
            .mirrors
            .iter()
            .map(|m| (m.base_url.as_str().to_string(), m.rank))
            .collect::<HashMap<_, _>>();

        assert_eq!(ranks["https://fast.example/"], 1);
        assert_eq!(ranks["https://slow.example/"], 2);
        assert_eq!(ranks["https://failed.example/"], 3);
        assert!(cache_path.is_file());
    }

    #[test]
    fn blend_policy_keeps_existing_rank_signal() {
        let results = vec![
            benchmark_result("https://current-best.example/", 1, Some(50.0)),
            benchmark_result("https://fast-but-low-priority.example/", 10, Some(100.0)),
            benchmark_result("https://middle.example/", 5, Some(75.0)),
        ];

        let ordered = ordered_benchmark_results(&results, RankApplyPolicy::Blend);
        let urls = ordered
            .iter()
            .map(|result| result.base_url.as_str())
            .collect::<Vec<_>>();

        assert_eq!(
            urls,
            vec![
                "https://current-best.example/",
                "https://middle.example/",
                "https://fast-but-low-priority.example/"
            ]
        );
    }

    #[tokio::test]
    async fn benchmark_uses_range_requests_and_records_throughput() {
        let server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/zig.tar.xz"))
            .and(header("range", "bytes=0-9"))
            .respond_with(ResponseTemplate::new(206).set_body_bytes(vec![7; 10]))
            .mount(&server)
            .await;

        let cache_path = tempdir().unwrap().path().join("mirrors.toml");
        let mut manager = MirrorManager::new(cache_path).unwrap();
        manager.mirrors = vec![test_mirror(&server.uri(), 1)];
        manager.mirrors_index = Some(MirrorsIndex {
            mirrors: manager.mirrors.clone(),
            last_synced: Utc::now(),
        });

        let results = manager
            .benchmark_mirrors(&Version::new(0, 15, 1), "zig.tar.xz", 10, 1)
            .await
            .unwrap();

        assert_eq!(results.len(), 1);
        assert!(results[0].is_success());
        assert_eq!(results[0].bytes_read, Some(10));
        assert_eq!(results[0].measured_layout, Some(Layout::Flat));
    }

    #[tokio::test]
    async fn benchmark_tries_alternate_layout_after_404() {
        let server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/0.15.1/zig.tar.xz"))
            .respond_with(ResponseTemplate::new(404))
            .mount(&server)
            .await;
        Mock::given(method("GET"))
            .and(path("/zig.tar.xz"))
            .respond_with(ResponseTemplate::new(206).set_body_bytes(vec![7; 10]))
            .mount(&server)
            .await;

        let cache_path = tempdir().unwrap().path().join("mirrors.toml");
        let mut manager = MirrorManager::new(cache_path).unwrap();
        let mut mirror = test_mirror(&server.uri(), 1);
        mirror.layout = Layout::Versioned;
        manager.mirrors = vec![mirror];
        manager.mirrors_index = Some(MirrorsIndex {
            mirrors: manager.mirrors.clone(),
            last_synced: Utc::now(),
        });

        let results = manager
            .benchmark_mirrors(&Version::new(0, 15, 1), "zig.tar.xz", 10, 1)
            .await
            .unwrap();

        assert!(results[0].is_success());
        assert_eq!(results[0].old_layout, Layout::Versioned);
        assert_eq!(results[0].measured_layout, Some(Layout::Flat));
        assert_eq!(manager.mirrors[0].layout, Layout::Versioned);
    }
}