//! REST HTTP API handlers for IAM
//!
//! Implements REST endpoints as specified in T050.S4:
//! - POST /api/v1/auth/token - Issue token
//! - POST /api/v1/auth/verify - Verify token
//! - GET /api/v1/users - List users
//! - POST /api/v1/users - Create user
//! - GET /api/v1/projects - List projects
//! - POST /api/v1/projects - Create project
//! - GET /health - Health check

use axum::{
    extract::State,
    http::StatusCode,
    routing::{get, post},
    Json, Router,
};
use iam_client::client::{IamClient, IamClientConfig};
use iam_types::{Principal, PrincipalKind, Scope};
use serde::{Deserialize, Serialize};

/// REST API state
#[derive(Clone)]
pub struct RestApiState {
    pub server_addr: String,
}

/// Standard REST error response
#[derive(Debug, Serialize)]
pub struct ErrorResponse {
    pub error: ErrorDetail,
    pub meta: ResponseMeta,
}

#[derive(Debug, Serialize)]
pub struct ErrorDetail {
    pub code: String,
    pub message: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub details: Option<serde_json::Value>,
}

#[derive(Debug, Serialize)]
pub struct ResponseMeta {
    pub request_id: String,
    pub timestamp: String,
}

impl ResponseMeta {
    fn new() -> Self {
        Self {
            request_id: uuid::Uuid::new_v4().to_string(),
            timestamp: chrono::Utc::now().to_rfc3339(),
        }
    }
}

/// Standard REST success response
#[derive(Debug, Serialize)]
pub struct SuccessResponse<T> {
    pub data: T,
    pub meta: ResponseMeta,
}

impl<T> SuccessResponse<T> {
    fn new(data: T) -> Self {
        Self {
            data,
            meta: ResponseMeta::new(),
        }
    }
}

/// Token issuance request
#[derive(Debug, Deserialize)]
pub struct TokenRequest {
    pub username: String,
    pub password: String,
    #[serde(default = "default_ttl")]
    pub ttl_seconds: u64,
}

fn default_ttl() -> u64 {
    3600 // 1 hour
}

/// Token response
#[derive(Debug, Serialize)]
pub struct TokenResponse {
    pub token: String,
    pub expires_at: String,
}

/// Token verification request
#[derive(Debug, Deserialize)]
pub struct VerifyRequest {
    pub token: String,
}

/// Token verification response
#[derive(Debug, Serialize)]
pub struct VerifyResponse {
    pub valid: bool,
    pub principal_id: Option<String>,
    pub principal_name: Option<String>,
    pub roles: Option<Vec<String>>,
}

/// User creation request
#[derive(Debug, Deserialize)]
pub struct CreateUserRequest {
    pub id: String,
    pub name: String,
}

/// User response
#[derive(Debug, Serialize)]
pub struct UserResponse {
    pub id: String,
    pub name: String,
    pub kind: String,
}

impl From<Principal> for UserResponse {
    fn from(p: Principal) -> Self {
        Self {
            id: p.id,
            name: p.name,
            kind: format!("{:?}", p.kind),
        }
    }
}

/// Users list response
#[derive(Debug, Serialize)]
pub struct UsersResponse {
    pub users: Vec<UserResponse>,
}

/// Project creation request (placeholder)
#[derive(Debug, Deserialize)]
pub struct CreateProjectRequest {
    pub id: String,
    pub name: String,
}

/// Project response (placeholder)
#[derive(Debug, Serialize)]
pub struct ProjectResponse {
    pub id: String,
    pub name: String,
}

/// Projects list response (placeholder)
#[derive(Debug, Serialize)]
pub struct ProjectsResponse {
    pub projects: Vec<ProjectResponse>,
}

/// Build the REST API router
pub fn build_router(state: RestApiState) -> Router {
    Router::new()
        .route("/api/v1/auth/token", post(issue_token))
        .route("/api/v1/auth/verify", post(verify_token))
        .route("/api/v1/users", get(list_users).post(create_user))
        .route("/api/v1/projects", get(list_projects).post(create_project))
        .route("/health", get(health_check))
        .with_state(state)
}

/// Health check endpoint
async fn health_check() -> (StatusCode, Json<SuccessResponse<serde_json::Value>>) {
    (
        StatusCode::OK,
        Json(SuccessResponse::new(
            serde_json::json!({ "status": "healthy" }),
        )),
    )
}

/// POST /api/v1/auth/token - Issue token
async fn issue_token(
    State(state): State<RestApiState>,
    Json(req): Json<TokenRequest>,
) -> Result<Json<SuccessResponse<TokenResponse>>, (StatusCode, Json<ErrorResponse>)> {
    let TokenRequest {
        username,
        password: _password,
        ttl_seconds,
    } = req;

    // Connect to IAM server
    let config = IamClientConfig::new(&state.server_addr).without_tls();
    let client = IamClient::connect(config).await.map_err(|e| {
        error_response(
            StatusCode::SERVICE_UNAVAILABLE,
            "SERVICE_UNAVAILABLE",
            &format!("Failed to connect: {}", e),
        )
    })?;

    // For demo purposes, create a user principal
    // In production, this would authenticate against a user store
    let principal = Principal {
        id: username.clone(),
        kind: PrincipalKind::User,
        name: username.clone(),
        org_id: None,
        project_id: None,
        email: None,
        oidc_sub: None,
        node_id: None,
        metadata: Default::default(),
        created_at: 0,
        updated_at: 0,
        enabled: true,
    };

    // Issue token
    let token = client
        .issue_token(&principal, vec![], Scope::System, ttl_seconds)
        .await
        .map_err(|e| {
            error_response(
                StatusCode::INTERNAL_SERVER_ERROR,
                "TOKEN_ISSUE_FAILED",
                &e.to_string(),
            )
        })?;

    let expires_at = chrono::Utc::now() + chrono::Duration::seconds(ttl_seconds as i64);

    Ok(Json(SuccessResponse::new(TokenResponse {
        token,
        expires_at: expires_at.to_rfc3339(),
    })))
}

/// POST /api/v1/auth/verify - Verify token
async fn verify_token(
    State(state): State<RestApiState>,
    Json(req): Json<VerifyRequest>,
) -> Result<Json<SuccessResponse<VerifyResponse>>, (StatusCode, Json<ErrorResponse>)> {
    // Connect to IAM server
    let config = IamClientConfig::new(&state.server_addr).without_tls();
    let client = IamClient::connect(config).await.map_err(|e| {
        error_response(
            StatusCode::SERVICE_UNAVAILABLE,
            "SERVICE_UNAVAILABLE",
            &format!("Failed to connect: {}", e),
        )
    })?;

    // Validate token
    let result = client.validate_token(&req.token).await;

    match result {
        Ok(claims) => Ok(Json(SuccessResponse::new(VerifyResponse {
            valid: true,
            principal_id: Some(claims.principal_id),
            principal_name: Some(claims.principal_name),
            roles: Some(claims.roles),
        }))),
        Err(_) => Ok(Json(SuccessResponse::new(VerifyResponse {
            valid: false,
            principal_id: None,
            principal_name: None,
            roles: None,
        }))),
    }
}

/// POST /api/v1/users - Create user
async fn create_user(
    State(state): State<RestApiState>,
    Json(req): Json<CreateUserRequest>,
) -> Result<(StatusCode, Json<SuccessResponse<UserResponse>>), (StatusCode, Json<ErrorResponse>)> {
    // Connect to IAM server
    let config = IamClientConfig::new(&state.server_addr).without_tls();
    let client = IamClient::connect(config).await.map_err(|e| {
        error_response(
            StatusCode::SERVICE_UNAVAILABLE,
            "SERVICE_UNAVAILABLE",
            &format!("Failed to connect: {}", e),
        )
    })?;

    // Create user
    let principal = client.create_user(&req.id, &req.name).await.map_err(|e| {
        error_response(
            StatusCode::INTERNAL_SERVER_ERROR,
            "USER_CREATE_FAILED",
            &e.to_string(),
        )
    })?;

    Ok((
        StatusCode::CREATED,
        Json(SuccessResponse::new(UserResponse::from(principal))),
    ))
}

/// GET /api/v1/users - List users
async fn list_users(
    State(state): State<RestApiState>,
) -> Result<Json<SuccessResponse<UsersResponse>>, (StatusCode, Json<ErrorResponse>)> {
    // Connect to IAM server
    let config = IamClientConfig::new(&state.server_addr).without_tls();
    let client = IamClient::connect(config).await.map_err(|e| {
        error_response(
            StatusCode::SERVICE_UNAVAILABLE,
            "SERVICE_UNAVAILABLE",
            &format!("Failed to connect: {}", e),
        )
    })?;

    // List users
    let principals = client.list_users().await.map_err(|e| {
        error_response(
            StatusCode::INTERNAL_SERVER_ERROR,
            "USER_LIST_FAILED",
            &e.to_string(),
        )
    })?;

    let users: Vec<UserResponse> = principals.into_iter().map(UserResponse::from).collect();

    Ok(Json(SuccessResponse::new(UsersResponse { users })))
}

/// GET /api/v1/projects - List projects (placeholder)
async fn list_projects(
    State(_state): State<RestApiState>,
) -> Result<Json<SuccessResponse<ProjectsResponse>>, (StatusCode, Json<ErrorResponse>)> {
    // Project management not yet implemented in IAM
    // Return placeholder response
    Ok(Json(SuccessResponse::new(ProjectsResponse {
        projects: vec![ProjectResponse {
            id: "(placeholder)".to_string(),
            name: "Project management via REST not yet implemented - use gRPC IamAdminService for scope/binding management".to_string(),
        }],
    })))
}

/// POST /api/v1/projects - Create project (placeholder)
async fn create_project(
    State(_state): State<RestApiState>,
    Json(req): Json<CreateProjectRequest>,
) -> Result<(StatusCode, Json<SuccessResponse<ProjectResponse>>), (StatusCode, Json<ErrorResponse>)>
{
    // Project management not yet implemented in IAM
    // Return placeholder response
    Ok((
        StatusCode::NOT_IMPLEMENTED,
        Json(SuccessResponse::new(ProjectResponse {
            id: req.id,
            name: format!(
                "Project '{}' - management via REST not yet implemented",
                req.name
            ),
        })),
    ))
}

/// Helper to create error response
fn error_response(
    status: StatusCode,
    code: &str,
    message: &str,
) -> (StatusCode, Json<ErrorResponse>) {
    (
        status,
        Json(ErrorResponse {
            error: ErrorDetail {
                code: code.to_string(),
                message: message.to_string(),
                details: None,
            },
            meta: ResponseMeta::new(),
        }),
    )
}