//! HTTP API wrapper for bulk_download.
//!
//! Start this server, then create download jobs with:
//! POST /jobs {"date":20260224,"concurrent":50,"force":false}

use anyhow::{Context, Result as AnyResult};
use axum::{
    extract::{Path, State},
    http::StatusCode,
    response::{Html, IntoResponse},
    routing::{get, post},
    Json, Router,
};
use serde::{Deserialize, Serialize};
use std::{
    collections::HashMap,
    env,
    net::SocketAddr,
    path::PathBuf,
    sync::{
        atomic::{AtomicU64, Ordering},
        Arc,
    },
};
use tokio::{process::Command, sync::RwLock};
use tracing::{error, info};

#[derive(Clone)]
struct AppState {
    jobs: Arc<RwLock<HashMap<String, JobRecord>>>,
    counter: Arc<AtomicU64>,
    bulk_bin: PathBuf,
    workdir: PathBuf,
}

#[derive(Debug, Deserialize)]
struct CreateJobRequest {
    /// Trading date in YYYYMMDD format, for example 20260224.
    date: u32,
    /// Download concurrency. Defaults to 50.
    #[serde(default = "default_concurrent")]
    concurrent: usize,
    /// true = force re-download, false = resume/incremental mode.
    #[serde(default)]
    force: bool,
}

fn default_concurrent() -> usize {
    50
}

#[derive(Debug, Clone, Serialize)]
struct JobRecord {
    id: String,
    date: u32,
    concurrent: usize,
    force: bool,
    status: JobStatus,
    started_at: String,
    finished_at: Option<String>,
    exit_code: Option<i32>,
    stdout_tail: Option<String>,
    stderr_tail: Option<String>,
    error: Option<String>,
}

#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "snake_case")]
enum JobStatus {
    Running,
    Succeeded,
    Failed,
}

#[derive(Debug, Serialize)]
struct CreateJobResponse {
    job_id: String,
    status: JobStatus,
    status_url: String,
}

#[derive(Debug, Serialize)]
struct HealthResponse {
    status: &'static str,
    bulk_bin: String,
    workdir: String,
}

#[derive(Debug, Serialize)]
struct ErrorResponse {
    error: String,
}

#[tokio::main]
async fn main() -> AnyResult<()> {
    tracing_subscriber::fmt()
        .with_env_filter(env::var("RUST_LOG").unwrap_or_else(|_| "info".to_string()))
        .init();

    let bulk_bin = resolve_bulk_download_bin();
    let workdir = resolve_workdir()?;
    let state = AppState {
        jobs: Arc::new(RwLock::new(HashMap::new())),
        counter: Arc::new(AtomicU64::new(1)),
        bulk_bin,
        workdir,
    };

    let app = Router::new()
        .route("/", get(index))
        .route("/ui", get(index))
        .route("/health", get(health))
        .route("/jobs", post(create_job).get(list_jobs))
        .route("/jobs/:job_id", get(get_job))
        .with_state(state.clone());

    let host = env::var("API_HOST").unwrap_or_else(|_| "0.0.0.0".to_string());
    let port = env::var("PORT")
        .or_else(|_| env::var("API_PORT"))
        .unwrap_or_else(|_| "7860".to_string())
        .parse::<u16>()
        .context("PORT/API_PORT must be a valid u16")?;
    let addr: SocketAddr = format!("{}:{}", host, port)
        .parse()
        .context("invalid API_HOST/API_PORT")?;

    info!("API server listening on http://{}", addr);
    info!("bulk_download binary: {}", state.bulk_bin.display());
    info!("working directory: {}", state.workdir.display());

    let listener = tokio::net::TcpListener::bind(addr).await?;
    axum::serve(listener, app).await?;
    Ok(())
}

async fn index() -> Html<&'static str> {
    Html(include_str!("../../static/index.html"))
}

async fn health(State(state): State<AppState>) -> Json<HealthResponse> {
    Json(HealthResponse {
        status: "ok",
        bulk_bin: state.bulk_bin.display().to_string(),
        workdir: state.workdir.display().to_string(),
    })
}

async fn list_jobs(State(state): State<AppState>) -> Json<Vec<JobRecord>> {
    let jobs = state.jobs.read().await;
    let mut result: Vec<JobRecord> = jobs.values().cloned().collect();
    result.sort_by(|a, b| b.started_at.cmp(&a.started_at));
    Json(result)
}

async fn get_job(
    State(state): State<AppState>,
    Path(job_id): Path<String>,
) -> Result<Json<JobRecord>, (StatusCode, Json<ErrorResponse>)> {
    let jobs = state.jobs.read().await;
    match jobs.get(&job_id) {
        Some(job) => Ok(Json(job.clone())),
        None => Err(api_error(StatusCode::NOT_FOUND, "job not found")),
    }
}

async fn create_job(
    State(state): State<AppState>,
    Json(req): Json<CreateJobRequest>,
) -> Result<impl IntoResponse, (StatusCode, Json<ErrorResponse>)> {
    validate_request(&req)?;

    let job_id = format!(
        "job-{}-{}",
        chrono::Utc::now().format("%Y%m%d%H%M%S"),
        state.counter.fetch_add(1, Ordering::Relaxed)
    );

    let record = JobRecord {
        id: job_id.clone(),
        date: req.date,
        concurrent: req.concurrent,
        force: req.force,
        status: JobStatus::Running,
        started_at: chrono::Utc::now().to_rfc3339(),
        finished_at: None,
        exit_code: None,
        stdout_tail: None,
        stderr_tail: None,
        error: None,
    };

    state.jobs.write().await.insert(job_id.clone(), record);

    let state_for_task = state.clone();
    let job_id_for_task = job_id.clone();
    tokio::spawn(async move {
        run_bulk_download_job(state_for_task, job_id_for_task, req).await;
    });

    Ok((
        StatusCode::ACCEPTED,
        Json(CreateJobResponse {
            job_id: job_id.clone(),
            status: JobStatus::Running,
            status_url: format!("/jobs/{}", job_id),
        }),
    ))
}

fn validate_request(req: &CreateJobRequest) -> Result<(), (StatusCode, Json<ErrorResponse>)> {
    let year = req.date / 10000;
    let month = (req.date / 100) % 100;
    let day = req.date % 100;

    if !(2000..=2099).contains(&year) || !(1..=12).contains(&month) || !(1..=31).contains(&day) {
        return Err(api_error(
            StatusCode::BAD_REQUEST,
            "date must be in YYYYMMDD format, for example 20260224",
        ));
    }

    if req.concurrent == 0 || req.concurrent > 1000 {
        return Err(api_error(
            StatusCode::BAD_REQUEST,
            "concurrent must be between 1 and 1000",
        ));
    }

    Ok(())
}

async fn run_bulk_download_job(state: AppState, job_id: String, req: CreateJobRequest) {
    let mut command = Command::new(&state.bulk_bin);
    command
        .arg(req.date.to_string())
        .arg(req.concurrent.to_string())
        .current_dir(&state.workdir);

    if req.force {
        command.arg("--force");
    }

    info!("starting job {}", job_id);
    let output = command.output().await;

    let mut jobs = state.jobs.write().await;
    if let Some(job) = jobs.get_mut(&job_id) {
        job.finished_at = Some(chrono::Utc::now().to_rfc3339());

        match output {
            Ok(output) => {
                let exit_code = output.status.code();
                job.exit_code = exit_code;
                job.stdout_tail = Some(tail_string(&String::from_utf8_lossy(&output.stdout), 64 * 1024));
                job.stderr_tail = Some(tail_string(&String::from_utf8_lossy(&output.stderr), 64 * 1024));
                job.status = if output.status.success() {
                    JobStatus::Succeeded
                } else {
                    JobStatus::Failed
                };

                info!("job {} finished with status {:?}", job_id, job.status);
            }
            Err(err) => {
                error!("job {} failed to start: {}", job_id, err);
                job.status = JobStatus::Failed;
                job.error = Some(err.to_string());
            }
        }
    }
}

fn api_error(status: StatusCode, message: impl Into<String>) -> (StatusCode, Json<ErrorResponse>) {
    (
        status,
        Json(ErrorResponse {
            error: message.into(),
        }),
    )
}

fn tail_string(s: &str, max_bytes: usize) -> String {
    if s.len() <= max_bytes {
        return s.to_string();
    }

    let mut start = s.len().saturating_sub(max_bytes);
    while start < s.len() && !s.is_char_boundary(start) {
        start += 1;
    }
    format!("...\n{}", &s[start..])
}

fn resolve_bulk_download_bin() -> PathBuf {
    if let Ok(path) = env::var("BULK_DOWNLOAD_BIN") {
        return PathBuf::from(path);
    }

    if let Ok(current_exe) = env::current_exe() {
        let sibling = current_exe.with_file_name("bulk_download");
        if sibling.exists() {
            return sibling;
        }
    }

    PathBuf::from("bulk_download")
}

fn resolve_workdir() -> AnyResult<PathBuf> {
    if let Ok(path) = env::var("BULK_DOWNLOAD_WORKDIR") {
        return Ok(PathBuf::from(path));
    }

    env::current_dir().context("cannot resolve current working directory")
}