//! Voice message cache management.
//!
//! Caches downloaded OGG voice files in ~/.cache/tele-tui/voice/
//! with LRU eviction when cache size exceeds limit.

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

/// Cache for voice message files
pub struct VoiceCache {
    cache_dir: PathBuf,
    /// file_id -> (path, size_bytes, access_count)
    files: HashMap<String, (PathBuf, u64, usize)>,
    access_counter: usize,
    max_size_bytes: u64,
}

impl VoiceCache {
    /// Creates a new VoiceCache with the given max size in MB
    pub fn new(max_size_mb: u64) -> Result<Self, String> {
        let cache_dir = dirs::cache_dir()
            .ok_or("Failed to get cache directory")?
            .join("tele-tui")
            .join("voice");

        fs::create_dir_all(&cache_dir)
            .map_err(|e| format!("Failed to create cache directory: {}", e))?;

        Ok(Self {
            cache_dir,
            files: HashMap::new(),
            access_counter: 0,
            max_size_bytes: max_size_mb * 1024 * 1024,
        })
    }

    /// Gets the path for a cached voice file, if it exists
    pub fn get(&mut self, file_id: &str) -> Option<PathBuf> {
        if let Some((path, _, access)) = self.files.get_mut(file_id) {
            // Update access count for LRU
            self.access_counter += 1;
            *access = self.access_counter;
            Some(path.clone())
        } else {
            None
        }
    }

    /// Stores a voice file in the cache
    pub fn store(&mut self, file_id: &str, source_path: &Path) -> Result<PathBuf, String> {
        // Copy file to cache
        let filename = format!("{}.ogg", file_id.replace('/', "_"));
        let dest_path = self.cache_dir.join(&filename);

        fs::copy(source_path, &dest_path)
            .map_err(|e| format!("Failed to copy voice file to cache: {}", e))?;

        // Get file size
        let size = fs::metadata(&dest_path)
            .map_err(|e| format!("Failed to get file size: {}", e))?
            .len();

        // Store in cache
        self.access_counter += 1;
        self.files
            .insert(file_id.to_string(), (dest_path.clone(), size, self.access_counter));

        // Check if we need to evict
        self.evict_if_needed()?;

        Ok(dest_path)
    }

    /// Returns the total size of all cached files
    pub fn total_size(&self) -> u64 {
        self.files.values().map(|(_, size, _)| size).sum()
    }

    /// Evicts oldest files until cache is under max size
    fn evict_if_needed(&mut self) -> Result<(), String> {
        while self.total_size() > self.max_size_bytes && !self.files.is_empty() {
            // Find least recently accessed file
            let oldest_id = self
                .files
                .iter()
                .min_by_key(|(_, (_, _, access))| access)
                .map(|(id, _)| id.clone());

            if let Some(id) = oldest_id {
                self.evict(&id)?;
            }
        }
        Ok(())
    }

    /// Evicts a specific file from cache
    fn evict(&mut self, file_id: &str) -> Result<(), String> {
        if let Some((path, _, _)) = self.files.remove(file_id) {
            fs::remove_file(&path).map_err(|e| format!("Failed to remove cached file: {}", e))?;
        }
        Ok(())
    }

    /// Clears all cached files
    #[allow(dead_code)]
    pub fn clear(&mut self) -> Result<(), String> {
        for (path, _, _) in self.files.values() {
            let _ = fs::remove_file(path); // Ignore errors
        }
        self.files.clear();
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::Write;

    #[test]
    fn test_voice_cache_creation() {
        let cache = VoiceCache::new(100);
        assert!(cache.is_ok());
    }

    #[test]
    fn test_cache_get_nonexistent() {
        let mut cache = VoiceCache::new(100).unwrap();
        assert!(cache.get("nonexistent").is_none());
    }

    #[test]
    fn test_cache_store_and_get() {
        let mut cache = VoiceCache::new(100).unwrap();

        // Create temporary file
        let temp_dir = std::env::temp_dir();
        let temp_file = temp_dir.join("test_voice.ogg");
        let mut file = fs::File::create(&temp_file).unwrap();
        file.write_all(b"test audio data").unwrap();

        // Store in cache
        let result = cache.store("test123", &temp_file);
        assert!(result.is_ok());

        // Get from cache
        let cached_path = cache.get("test123");
        assert!(cached_path.is_some());
        assert!(cached_path.unwrap().exists());

        // Cleanup
        fs::remove_file(&temp_file).unwrap();
    }
}