use std::{
  collections::{HashMap, HashSet},
  fs,
  path::{Path, PathBuf},
};

use indicatif::{ProgressBar, ProgressStyle};

use crate::{
  cli::SyncArgs,
  error::{PakkerError, Result},
  fetch::Fetcher,
  model::{Config, LockFile},
  platform::{CurseForgePlatform, ModrinthPlatform, PlatformClient},
};

enum SyncChange {
  Addition(PathBuf, String), // (file_path, project_name)
  Removal(String),           // project_pakku_id
}

#[expect(
  clippy::expect_used,
  reason = "spinner template is a string literal and is always valid"
)]
pub async fn execute(
  args: SyncArgs,
  global_yes: bool,
  lockfile_path: &Path,
  config_path: &Path,
) -> Result<()> {
  log::info!("Synchronizing with lockfile");

  let lockfile_dir = lockfile_path.parent().unwrap_or_else(|| Path::new("."));
  let config_dir = config_path.parent().unwrap_or_else(|| Path::new("."));

  let mut lockfile = LockFile::load(lockfile_dir)?;
  let config = Config::load(config_dir)?;

  // Detect changes
  let changes = detect_changes(&lockfile, &config);

  if changes.is_empty() {
    println!("✓ Everything is in sync");
    return Ok(());
  }

  // Filter changes based on flags
  let mut additions = Vec::new();
  let mut removals = Vec::new();

  for change in changes {
    match change {
      SyncChange::Addition(path, name) => additions.push((path, name)),
      SyncChange::Removal(id) => removals.push(id),
    }
  }

  // Apply filters
  let no_filter = !args.additions && !args.removals;

  let spinner = ProgressBar::new_spinner();
  spinner.set_style(
    ProgressStyle::default_spinner()
      .template("{spinner:.green} {msg}")
      .expect("spinner template is valid"),
  );

  if no_filter || args.additions {
    let mut file_hashes = Vec::new();

    for (file_path, _) in &additions {
      spinner
        .set_message(format!("Processing addition: {}", file_path.display()));
      if crate::ui_utils::prompt_yes_no(
        &format!("Add {} to lockfile?", file_path.display()),
        false,
        global_yes,
      )? && let Ok(file_data) = fs::read(file_path)
      {
        use sha1::Digest;
        let mut hasher = sha1::Sha1::new();
        hasher.update(&file_data);
        let hash =
          crate::utils::hash::hash_to_hex(hasher.finalize().as_slice());
        file_hashes.push(FileHash {
          path: file_path.clone(),
          hash,
        });
      }
    }

    if !file_hashes.is_empty() {
      let fallback_hashes = file_hashes.clone();
      let result = add_files_batch(&mut lockfile, file_hashes).await;
      if let Err(e) = result {
        log::warn!(
          "Batch lookup failed, falling back to individual lookups: {e}"
        );
        for fh in fallback_hashes {
          if let Err(e) =
            add_file_to_lockfile(&mut lockfile, &fh.path, &config).await
          {
            log::warn!("Failed to add {}: {}", fh.path.display(), e);
          }
        }
      }
    }
  }

  if no_filter || args.removals {
    for pakku_id in &removals {
      if let Some(project) = lockfile
        .projects
        .iter()
        .find(|p| p.pakku_id.as_ref() == Some(pakku_id))
      {
        let name = project
          .name
          .values()
          .next()
          .map(std::string::String::as_str)
          .or(project.pakku_id.as_deref())
          .unwrap_or("unknown");
        spinner.set_message(format!("Processing removal: {name}"));
        if crate::ui_utils::prompt_yes_no(
          &format!("Remove {name} from lockfile?"),
          false,
          global_yes,
        )? {
          lockfile
            .remove_project(pakku_id)
            .ok_or_else(|| PakkerError::ProjectNotFound(pakku_id.clone()))?;
        }
      }
    }
  }

  spinner.finish_and_clear();

  // Save changes
  lockfile.save(lockfile_dir)?;

  // Fetch missing files
  let fetcher = Fetcher::new(".");
  fetcher.sync(&lockfile, &config).await?;

  println!("✓ Sync complete");
  Ok(())
}

fn detect_changes(lockfile: &LockFile, config: &Config) -> Vec<SyncChange> {
  let mut changes = Vec::new();

  // Get paths for each project type
  let paths = config.paths.clone();
  let mods_path = paths
    .get("mods")
    .map_or("mods", std::string::String::as_str);

  // Build map of lockfile projects by file path
  let mut lockfile_files: HashMap<PathBuf, String> = HashMap::new();
  for project in &lockfile.projects {
    for file in &project.files {
      let file_path = PathBuf::from(mods_path).join(&file.file_name);
      if let Some(ref pakku_id) = project.pakku_id {
        lockfile_files.insert(file_path, pakku_id.clone());
      }
    }
  }

  // Scan filesystem for additions
  if let Ok(entries) = fs::read_dir(mods_path) {
    for entry in entries.flatten() {
      let path = entry.path();
      if path.is_file()
        && let Some(ext) = path.extension()
        && ext == "jar"
        && !lockfile_files.contains_key(&path)
      {
        let name = path
          .file_name()
          .map(|n| n.to_string_lossy().to_string())
          .unwrap_or_default();
        changes.push(SyncChange::Addition(path, name));
      }
    }
  }

  // Check for removals (projects in lockfile but files missing)
  let filesystem_files: HashSet<_> = fs::read_dir(mods_path).map_or_else(
    |_| HashSet::new(),
    |entries| {
      entries
        .flatten()
        .map(|e| e.path())
        .filter(|p| p.is_file())
        .collect()
    },
  );

  for (lockfile_path, pakku_id) in &lockfile_files {
    if !filesystem_files.contains(lockfile_path) {
      changes.push(SyncChange::Removal(pakku_id.clone()));
    }
  }

  changes
}

async fn add_file_to_lockfile(
  lockfile: &mut LockFile,
  file_path: &Path,
  _config: &Config,
) -> Result<()> {
  use sha1::Digest;

  // Try to identify the file by hash lookup
  let modrinth = ModrinthPlatform::new();
  let curseforge = CurseForgePlatform::new(None);

  // Compute file hash
  let file_data = fs::read(file_path)?;
  let mut hasher = sha1::Sha1::new();
  hasher.update(&file_data);
  let hash = crate::utils::hash::hash_to_hex(hasher.finalize().as_slice());

  // Try Modrinth first (SHA-1 hash)
  if let Ok(Some(project)) = modrinth.lookup_by_hash(&hash).await {
    lockfile.add_project(project);
    println!("✓ Added {} (from Modrinth)", file_path.display());
    return Ok(());
  }

  // Try CurseForge (Murmur2 hash computed from file)
  if let Ok(Some(project)) = curseforge.lookup_by_hash(&hash).await {
    lockfile.add_project(project);
    println!("✓ Added {} (from CurseForge)", file_path.display());
    return Ok(());
  }

  println!("⚠ Could not identify {}, skipping", file_path.display());
  Ok(())
}

#[derive(Clone)]
struct FileHash {
  path: PathBuf,
  hash: String,
}

async fn add_files_batch(
  lockfile: &mut LockFile,
  file_hashes: Vec<FileHash>,
) -> Result<()> {
  if file_hashes.is_empty() {
    return Ok(());
  }

  let modrinth = ModrinthPlatform::new();

  let hashes: Vec<String> =
    file_hashes.iter().map(|fh| fh.hash.clone()).collect();

  let projects = modrinth
    .request_projects_from_hashes(&hashes, "sha1")
    .await?;

  let mut matched_indices: std::collections::HashSet<usize> =
    std::collections::HashSet::new();
  let mut added_pakku_ids: std::collections::HashSet<String> =
    std::collections::HashSet::new();

  for project in &projects {
    let pakku_id = match &project.pakku_id {
      Some(id) => id.clone(),
      None => continue,
    };
    if added_pakku_ids.contains(&pakku_id) {
      continue;
    }
    for file_info in &project.files {
      for (idx, fh) in file_hashes.iter().enumerate() {
        if !matched_indices.contains(&idx)
          && file_info
            .hashes
            .get("sha1")
            .map(std::string::String::as_str)
            == Some(&fh.hash)
        {
          lockfile.add_project(project.clone());
          added_pakku_ids.insert(pakku_id.clone());
          matched_indices.insert(idx);
          println!("✓ Added {} (from Modrinth)", fh.path.display());
          break;
        }
      }
    }
  }

  for (idx, fh) in file_hashes.iter().enumerate() {
    if matched_indices.contains(&idx) {
      continue;
    }
    println!("⚠ Could not identify {}, skipping", fh.path.display());
  }

  Ok(())
}