// Copyright (c) 2026 Volkov Pavel | DevITWay
// SPDX-License-Identifier: MIT

use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};
use std::fs;
use std::path::{Path, PathBuf};
use std::time::{SystemTime, UNIX_EPOCH};
use thiserror::Error;
use uuid::Uuid;

const TOKEN_PREFIX: &str = "nra_";

/// API Token metadata stored on disk
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TokenInfo {
    pub token_hash: String,
    pub user: String,
    pub created_at: u64,
    pub expires_at: u64,
    pub last_used: Option<u64>,
    pub description: Option<String>,
}

/// Token store for managing API tokens
#[derive(Clone)]
pub struct TokenStore {
    storage_path: PathBuf,
}

impl TokenStore {
    /// Create a new token store
    pub fn new(storage_path: &Path) -> Self {
        // Ensure directory exists
        let _ = fs::create_dir_all(storage_path);
        Self {
            storage_path: storage_path.to_path_buf(),
        }
    }

    /// Generate a new API token for a user
    pub fn create_token(
        &self,
        user: &str,
        ttl_days: u64,
        description: Option<String>,
    ) -> Result<String, TokenError> {
        // Generate random token
        let raw_token = format!(
            "{}{}",
            TOKEN_PREFIX,
            Uuid::new_v4().to_string().replace("-", "")
        );
        let token_hash = hash_token(&raw_token);

        let now = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap_or_default()
            .as_secs();

        let expires_at = now + (ttl_days * 24 * 60 * 60);

        let info = TokenInfo {
            token_hash: token_hash.clone(),
            user: user.to_string(),
            created_at: now,
            expires_at,
            last_used: None,
            description,
        };

        // Save to file
        let file_path = self
            .storage_path
            .join(format!("{}.json", &token_hash[..16]));
        let json =
            serde_json::to_string_pretty(&info).map_err(|e| TokenError::Storage(e.to_string()))?;
        fs::write(&file_path, json).map_err(|e| TokenError::Storage(e.to_string()))?;

        Ok(raw_token)
    }

    /// Verify a token and return user info if valid
    pub fn verify_token(&self, token: &str) -> Result<String, TokenError> {
        if !token.starts_with(TOKEN_PREFIX) {
            return Err(TokenError::InvalidFormat);
        }

        let token_hash = hash_token(token);
        let file_path = self
            .storage_path
            .join(format!("{}.json", &token_hash[..16]));

        if !file_path.exists() {
            return Err(TokenError::NotFound);
        }

        let content =
            fs::read_to_string(&file_path).map_err(|e| TokenError::Storage(e.to_string()))?;
        let mut info: TokenInfo =
            serde_json::from_str(&content).map_err(|e| TokenError::Storage(e.to_string()))?;

        // Verify hash matches
        if info.token_hash != token_hash {
            return Err(TokenError::NotFound);
        }

        // Check expiration
        let now = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap_or_default()
            .as_secs();

        if now > info.expires_at {
            return Err(TokenError::Expired);
        }

        // Update last_used
        info.last_used = Some(now);
        if let Ok(json) = serde_json::to_string_pretty(&info) {
            let _ = fs::write(&file_path, json);
        }

        Ok(info.user)
    }

    /// List all tokens for a user
    pub fn list_tokens(&self, user: &str) -> Vec<TokenInfo> {
        let mut tokens = Vec::new();

        if let Ok(entries) = fs::read_dir(&self.storage_path) {
            for entry in entries.flatten() {
                if let Ok(content) = fs::read_to_string(entry.path()) {
                    if let Ok(info) = serde_json::from_str::<TokenInfo>(&content) {
                        if info.user == user {
                            tokens.push(info);
                        }
                    }
                }
            }
        }

        tokens.sort_by(|a, b| b.created_at.cmp(&a.created_at));
        tokens
    }

    /// Revoke a token by its hash prefix
    pub fn revoke_token(&self, hash_prefix: &str) -> Result<(), TokenError> {
        let file_path = self.storage_path.join(format!("{}.json", hash_prefix));

        if !file_path.exists() {
            return Err(TokenError::NotFound);
        }

        fs::remove_file(&file_path).map_err(|e| TokenError::Storage(e.to_string()))?;

        Ok(())
    }

    /// Revoke all tokens for a user
    pub fn revoke_all_for_user(&self, user: &str) -> usize {
        let mut count = 0;

        if let Ok(entries) = fs::read_dir(&self.storage_path) {
            for entry in entries.flatten() {
                if let Ok(content) = fs::read_to_string(entry.path()) {
                    if let Ok(info) = serde_json::from_str::<TokenInfo>(&content) {
                        if info.user == user && fs::remove_file(entry.path()).is_ok() {
                            count += 1;
                        }
                    }
                }
            }
        }

        count
    }
}

/// Hash a token using SHA256
fn hash_token(token: &str) -> String {
    let mut hasher = Sha256::new();
    hasher.update(token.as_bytes());
    format!("{:x}", hasher.finalize())
}

#[derive(Debug, Error)]
pub enum TokenError {
    #[error("Invalid token format")]
    InvalidFormat,

    #[error("Token not found")]
    NotFound,

    #[error("Token expired")]
    Expired,

    #[error("Storage error: {0}")]
    Storage(String),
}

#[cfg(test)]
mod tests {
    use super::*;
    use tempfile::TempDir;

    #[test]
    fn test_create_token() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        let token = store
            .create_token("testuser", 30, Some("Test token".to_string()))
            .unwrap();

        assert!(token.starts_with("nra_"));
        assert_eq!(token.len(), 4 + 32); // prefix + uuid without dashes
    }

    #[test]
    fn test_verify_valid_token() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        let token = store.create_token("testuser", 30, None).unwrap();
        let user = store.verify_token(&token).unwrap();

        assert_eq!(user, "testuser");
    }

    #[test]
    fn test_verify_invalid_format() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        let result = store.verify_token("invalid_token");
        assert!(matches!(result, Err(TokenError::InvalidFormat)));
    }

    #[test]
    fn test_verify_not_found() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        let result = store.verify_token("nra_00000000000000000000000000000000");
        assert!(matches!(result, Err(TokenError::NotFound)));
    }

    #[test]
    fn test_verify_expired_token() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        // Create token and manually set it as expired
        let token = store.create_token("testuser", 1, None).unwrap();
        let token_hash = hash_token(&token);
        let file_path = temp_dir.path().join(format!("{}.json", &token_hash[..16]));

        // Read and modify the token to be expired
        let content = std::fs::read_to_string(&file_path).unwrap();
        let mut info: TokenInfo = serde_json::from_str(&content).unwrap();
        info.expires_at = 0; // Set to epoch (definitely expired)
        std::fs::write(&file_path, serde_json::to_string(&info).unwrap()).unwrap();

        // Token should now be expired
        let result = store.verify_token(&token);
        assert!(matches!(result, Err(TokenError::Expired)));
    }

    #[test]
    fn test_list_tokens() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        store.create_token("user1", 30, None).unwrap();
        store.create_token("user1", 30, None).unwrap();
        store.create_token("user2", 30, None).unwrap();

        let user1_tokens = store.list_tokens("user1");
        assert_eq!(user1_tokens.len(), 2);

        let user2_tokens = store.list_tokens("user2");
        assert_eq!(user2_tokens.len(), 1);

        let unknown_tokens = store.list_tokens("unknown");
        assert_eq!(unknown_tokens.len(), 0);
    }

    #[test]
    fn test_revoke_token() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        let token = store.create_token("testuser", 30, None).unwrap();
        let token_hash = hash_token(&token);
        let hash_prefix = &token_hash[..16];

        // Verify token works
        assert!(store.verify_token(&token).is_ok());

        // Revoke
        store.revoke_token(hash_prefix).unwrap();

        // Verify token no longer works
        let result = store.verify_token(&token);
        assert!(matches!(result, Err(TokenError::NotFound)));
    }

    #[test]
    fn test_revoke_nonexistent_token() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        let result = store.revoke_token("nonexistent12345");
        assert!(matches!(result, Err(TokenError::NotFound)));
    }

    #[test]
    fn test_revoke_all_for_user() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        store.create_token("user1", 30, None).unwrap();
        store.create_token("user1", 30, None).unwrap();
        store.create_token("user2", 30, None).unwrap();

        let revoked = store.revoke_all_for_user("user1");
        assert_eq!(revoked, 2);

        assert_eq!(store.list_tokens("user1").len(), 0);
        assert_eq!(store.list_tokens("user2").len(), 1);
    }

    #[test]
    fn test_token_updates_last_used() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        let token = store.create_token("testuser", 30, None).unwrap();

        // First verification
        store.verify_token(&token).unwrap();

        // Check last_used is set
        let tokens = store.list_tokens("testuser");
        assert!(tokens[0].last_used.is_some());
    }

    #[test]
    fn test_token_with_description() {
        let temp_dir = TempDir::new().unwrap();
        let store = TokenStore::new(temp_dir.path());

        store
            .create_token("testuser", 30, Some("CI/CD Pipeline".to_string()))
            .unwrap();

        let tokens = store.list_tokens("testuser");
        assert_eq!(tokens[0].description, Some("CI/CD Pipeline".to_string()));
    }
}