//! Central encrypted secret storage for provider/ACME credentials.
//! Plaintext exists only for the duration of an explicit read/write operation.
use anyhow::{ensure, Context, Result};
use rand::{rngs::OsRng, RngCore};
use ring::aead::{Aad, LessSafeKey, Nonce, UnboundKey, AES_256_GCM};
use serde::Serialize;
use sqlx::Row;
use std::{
    fs::{self, OpenOptions},
    io::{Read, Write},
    path::{Path, PathBuf},
};
use zeroize::{Zeroize, Zeroizing};

const KEY_BYTES: usize = 32;
const NONCE_BYTES: usize = 12;
const ENCRYPTION_VERSION: i64 = 1;
const MAX_SECRET_BYTES: usize = 64 * 1024;

#[derive(Debug, Clone, Serialize)]
pub struct SecretMetadata {
    pub secret_id: String,
    pub provider: String,
    pub encryption_version: i64,
    pub metadata: serde_json::Value,
    pub created_at: i64,
    pub updated_at: i64,
}

fn secrets_dir(data_dir: &Path) -> PathBuf {
    data_dir.join("secrets")
}
pub fn master_key_path(data_dir: &Path) -> PathBuf {
    secrets_dir(data_dir).join("master.key")
}

fn private_directory(path: &Path) -> Result<()> {
    if !path.exists() {
        fs::create_dir_all(path)?;
    }
    let metadata = fs::symlink_metadata(path)?;
    ensure!(
        metadata.is_dir() && !metadata.file_type().is_symlink(),
        "secret store directory must be a real directory"
    );
    #[cfg(unix)]
    {
        use std::os::unix::fs::PermissionsExt;
        if metadata.permissions().mode() & 0o077 != 0 {
            fs::set_permissions(path, fs::Permissions::from_mode(0o700))?;
        }
    }
    Ok(())
}

fn read_key(path: &Path) -> Result<Zeroizing<[u8; KEY_BYTES]>> {
    let metadata = fs::symlink_metadata(path).context("secret store master key is missing")?;
    ensure!(
        metadata.is_file() && !metadata.file_type().is_symlink(),
        "secret store master key must be a regular file"
    );
    ensure!(metadata.len() == KEY_BYTES as u64, "invalid secret store master key size");
    #[cfg(unix)]
    {
        use std::os::unix::fs::PermissionsExt;
        ensure!(
            metadata.permissions().mode() & 0o077 == 0,
            "secret store master key must have mode 0600"
        );
    }
    let mut bytes = Zeroizing::new([0u8; KEY_BYTES]);
    let mut options = OpenOptions::new();
    options.read(true);
    #[cfg(unix)]
    {
        use std::os::unix::fs::OpenOptionsExt;
        options.custom_flags(libc::O_NOFOLLOW);
    }
    let mut file = options.open(path)?;
    file.read_exact(bytes.as_mut())?;
    let mut extra = [0u8; 1];
    ensure!(file.read(&mut extra)? == 0, "invalid secret store master key size");
    Ok(bytes)
}

pub fn initialize(data_dir: &Path) -> Result<()> {
    let directory = secrets_dir(data_dir);
    private_directory(&directory)?;
    let path = master_key_path(data_dir);
    if path.exists() {
        let _ = read_key(&path)?;
        return Ok(());
    }
    let mut key = Zeroizing::new([0u8; KEY_BYTES]);
    OsRng.fill_bytes(key.as_mut());
    let mut options = OpenOptions::new();
    options.write(true).create_new(true);
    #[cfg(unix)]
    {
        use std::os::unix::fs::OpenOptionsExt;
        options.mode(0o600).custom_flags(libc::O_NOFOLLOW);
    }
    match options.open(&path) {
        Ok(mut file) => {
            file.write_all(key.as_ref())?;
            file.sync_all()?;
        }
        Err(error) if error.kind() == std::io::ErrorKind::AlreadyExists => {
            let _ = read_key(&path)?;
        }
        Err(error) => return Err(error.into()),
    }
    #[cfg(unix)]
    {
        use std::os::unix::fs::PermissionsExt;
        fs::set_permissions(&path, fs::Permissions::from_mode(0o600))?;
    }
    Ok(())
}

fn validate_identity(secret_id: &str, provider: &str) -> Result<()> {
    ensure!(
        !secret_id.is_empty()
            && secret_id.len() <= 256
            && secret_id
                .bytes()
                .all(|b| b.is_ascii_alphanumeric() || matches!(b, b'/' | b'_' | b'-' | b'.')),
        "invalid secret id"
    );
    ensure!(
        !provider.is_empty()
            && provider.len() <= 64
            && provider
                .bytes()
                .all(|b| b.is_ascii_alphanumeric() || matches!(b, b'_' | b'-' | b'.')),
        "invalid secret provider"
    );
    Ok(())
}

fn aad(secret_id: &str, provider: &str) -> Vec<u8> {
    format!("rustproxy-secret-v{ENCRYPTION_VERSION}\0{secret_id}\0{provider}").into_bytes()
}

fn key(data_dir: &Path) -> Result<LessSafeKey> {
    let bytes = read_key(&master_key_path(data_dir))?;
    let unbound = UnboundKey::new(&AES_256_GCM, bytes.as_ref())
        .map_err(|_| anyhow::anyhow!("cannot initialize secret store cipher"))?;
    Ok(LessSafeKey::new(unbound))
}

pub async fn put(
    store: &crate::db::Store,
    data_dir: &Path,
    secret_id: &str,
    provider: &str,
    plaintext: &[u8],
    metadata: serde_json::Value,
) -> Result<()> {
    validate_identity(secret_id, provider)?;
    ensure!(!plaintext.is_empty() && plaintext.len() <= MAX_SECRET_BYTES, "invalid secret size");
    let metadata = serde_json::to_string(&metadata)?;
    ensure!(metadata.len() <= 4096, "secret metadata is too large");
    initialize(data_dir)?;
    let cipher = key(data_dir)?;
    let mut nonce = [0u8; NONCE_BYTES];
    OsRng.fill_bytes(&mut nonce);
    let mut ciphertext = Zeroizing::new(plaintext.to_vec());
    cipher
        .seal_in_place_append_tag(
            Nonce::assume_unique_for_key(nonce),
            Aad::from(aad(secret_id, provider)),
            &mut *ciphertext,
        )
        .map_err(|_| anyhow::anyhow!("secret encryption failed"))?;
    let now = crate::auth::now();
    sqlx::query(
        "INSERT INTO secret_store(secret_id, provider, encryption_version, nonce, ciphertext, metadata, created_at, updated_at) \
         VALUES(?, ?, ?, ?, ?, ?, ?, ?) \
         ON CONFLICT(secret_id) DO UPDATE SET provider=excluded.provider, encryption_version=excluded.encryption_version, \
         nonce=excluded.nonce, ciphertext=excluded.ciphertext, metadata=excluded.metadata, updated_at=excluded.updated_at",
    )
    .bind(secret_id)
    .bind(provider)
    .bind(ENCRYPTION_VERSION)
    .bind(nonce.to_vec())
    .bind(ciphertext.as_slice())
    .bind(metadata)
    .bind(now)
    .bind(now)
    .execute(&store.pool)
    .await?;
    Ok(())
}

pub async fn get(
    store: &crate::db::Store,
    data_dir: &Path,
    secret_id: &str,
    expected_provider: Option<&str>,
) -> Result<Zeroizing<Vec<u8>>> {
    let row = sqlx::query(
        "SELECT provider, encryption_version, nonce, ciphertext FROM secret_store WHERE secret_id = ?",
    )
    .bind(secret_id)
    .fetch_optional(&store.pool)
    .await?
    .ok_or_else(|| anyhow::anyhow!("secret not found"))?;
    let provider: String = row.try_get("provider")?;
    if let Some(expected) = expected_provider {
        ensure!(provider == expected, "secret provider mismatch");
    }
    validate_identity(secret_id, &provider)?;
    let version: i64 = row.try_get("encryption_version")?;
    ensure!(version == ENCRYPTION_VERSION, "unsupported secret encryption version");
    let nonce: Vec<u8> = row.try_get("nonce")?;
    ensure!(nonce.len() == NONCE_BYTES, "invalid secret nonce");
    let mut ciphertext = Zeroizing::new(row.try_get::<Vec<u8>, _>("ciphertext")?);
    ensure!(
        ciphertext.len() >= AES_256_GCM.tag_len() && ciphertext.len() <= MAX_SECRET_BYTES + AES_256_GCM.tag_len(),
        "invalid encrypted secret size"
    );
    let mut nonce_bytes = [0u8; NONCE_BYTES];
    nonce_bytes.copy_from_slice(&nonce);
    let cipher = key(data_dir)?;
    let plaintext = cipher
        .open_in_place(
            Nonce::assume_unique_for_key(nonce_bytes),
            Aad::from(aad(secret_id, &provider)),
            ciphertext.as_mut(),
        )
        .map_err(|_| anyhow::anyhow!("secret authentication failed"))?;
    let output = Zeroizing::new(plaintext.to_vec());
    ciphertext.zeroize();
    Ok(output)
}

pub async fn delete(store: &crate::db::Store, secret_id: &str) -> Result<bool> {
    let result = sqlx::query("DELETE FROM secret_store WHERE secret_id = ?")
        .bind(secret_id)
        .execute(&store.pool)
        .await?;
    Ok(result.rows_affected() > 0)
}

pub async fn metadata(store: &crate::db::Store) -> Result<Vec<SecretMetadata>> {
    let rows = sqlx::query(
        "SELECT secret_id, provider, encryption_version, metadata, created_at, updated_at FROM secret_store ORDER BY secret_id",
    )
    .fetch_all(&store.pool)
    .await?;
    rows.into_iter()
        .map(|row| {
            let raw: String = row.try_get("metadata")?;
            Ok(SecretMetadata {
                secret_id: row.try_get("secret_id")?,
                provider: row.try_get("provider")?,
                encryption_version: row.try_get("encryption_version")?,
                metadata: serde_json::from_str(&raw).unwrap_or(serde_json::Value::Null),
                created_at: row.try_get("created_at")?,
                updated_at: row.try_get("updated_at")?,
            })
        })
        .collect()
}

pub async fn validate_all(store: &crate::db::Store, data_dir: &Path) -> Result<()> {
    for item in metadata(store).await? {
        let value = get(store, data_dir, &item.secret_id, Some(&item.provider)).await?;
        ensure!(!value.is_empty(), "empty secret store record");
    }
    Ok(())
}

pub fn acme_secret_id(certificate_id: &str, provider: &str) -> String {
    format!("acme/{certificate_id}/{provider}/credential")
}

pub async fn migrate_acme_credentials(
    store: &crate::db::Store,
    data_dir: &Path,
    cert_dir: &Path,
) -> Result<usize> {
    initialize(data_dir)?;
    let root = cert_dir.join("acme");
    if !root.exists() {
        return Ok(0);
    }
    let root_meta = fs::symlink_metadata(&root)?;
    ensure!(root_meta.is_dir() && !root_meta.file_type().is_symlink(), "invalid ACME directory");
    let mut migrated = 0usize;
    for entry in fs::read_dir(&root)? {
        let entry = entry?;
        let profile_dir = entry.path();
        let meta = fs::symlink_metadata(&profile_dir)?;
        if !meta.is_dir() || meta.file_type().is_symlink() {
            continue;
        }
        let profile_path = profile_dir.join("profile.json");
        if !profile_path.is_file() {
            continue;
        }
        let profile: serde_json::Value = serde_json::from_slice(&fs::read(&profile_path)?)?;
        let provider = profile.get("provider").and_then(serde_json::Value::as_str).unwrap_or("");
        let certificate_id = profile
            .get("certificate_id")
            .and_then(serde_json::Value::as_str)
            .unwrap_or("");
        if provider == "http01" {
            continue;
        }
        validate_identity(&acme_secret_id(certificate_id, provider), provider)?;
        let credential_path = profile_dir.join(format!("{provider}.ini"));
        if !credential_path.exists() {
            continue;
        }
        let credential_meta = fs::symlink_metadata(&credential_path)?;
        ensure!(
            credential_meta.is_file()
                && !credential_meta.file_type().is_symlink()
                && credential_meta.len() <= MAX_SECRET_BYTES as u64,
            "unsafe legacy ACME credential file"
        );
        #[cfg(unix)]
        {
            use std::os::unix::fs::PermissionsExt;
            ensure!(
                credential_meta.permissions().mode() & 0o077 == 0,
                "legacy ACME credential file must be private"
            );
        }
        let mut plaintext = Zeroizing::new(fs::read(&credential_path)?);
        ensure!(!plaintext.is_empty(), "empty legacy ACME credential file");
        put(
            store,
            data_dir,
            &acme_secret_id(certificate_id, provider),
            provider,
            plaintext.as_ref(),
            serde_json::json!({"source":"acme_credential_migration","certificate_id":certificate_id}),
        )
        .await?;
        plaintext.zeroize();
        fs::remove_file(&credential_path).context("legacy ACME credential was encrypted but could not be removed")?;
        migrated += 1;
    }
    Ok(migrated)
}

pub fn read_master_key_for_backup(data_dir: &Path) -> Result<Zeroizing<[u8; KEY_BYTES]>> {
    initialize(data_dir)?;
    read_key(&master_key_path(data_dir))
}

pub fn write_restored_master_key(data_dir: &Path, key: &[u8]) -> Result<()> {
    ensure!(key.len() == KEY_BYTES, "invalid restored secret store key");
    let directory = secrets_dir(data_dir);
    private_directory(&directory)?;
    let path = master_key_path(data_dir);
    ensure!(!path.exists(), "restored secret store key already exists");
    let mut options = OpenOptions::new();
    options.write(true).create_new(true);
    #[cfg(unix)]
    {
        use std::os::unix::fs::OpenOptionsExt;
        options.mode(0o600).custom_flags(libc::O_NOFOLLOW);
    }
    let mut file = options.open(&path)?;
    file.write_all(key)?;
    file.sync_all()?;
    Ok(())
}

#[cfg(test)]
include!("secret_store/tests.rs");