use axum::{
    extract::{Path, Query, State},
    http::StatusCode,
    response::IntoResponse,
    Json,
};
use serde::Deserialize;
use serde_json::json;
use uuid::Uuid;
use validator::Validate;

use plc_platform_core::util::response::ApiErr;

use crate::{service::station as station_service, AppState};

const STATION_TYPES: &[&str] = &[
    "load",
    "dry_in",
    "dry_step",
    "dry_out",
    "fire_in",
    "fire_step",
    "fire_out",
    "transfer",
    "unload",
    "return",
];

const SIGNAL_ROLES: &[&str] = &[
    "presence", "vacancy", "arrived", "allow_in", "done", "fault",
];

fn validate_station_type(value: &str) -> Result<(), ApiErr> {
    if STATION_TYPES.contains(&value) {
        Ok(())
    } else {
        Err(ApiErr::BadRequest(
            format!("invalid station_type: {}", value),
            Some(json!({ "allowed": STATION_TYPES })),
        ))
    }
}

fn validate_signal_role(value: &str) -> Result<(), ApiErr> {
    if SIGNAL_ROLES.contains(&value) {
        Ok(())
    } else {
        Err(ApiErr::BadRequest(
            format!("invalid signal_role: {}", value),
            Some(json!({ "allowed": SIGNAL_ROLES })),
        ))
    }
}

#[derive(Debug, Deserialize, Validate)]
pub struct ListStationQuery {
    #[validate(length(min = 1, max = 50))]
    pub line_code: Option<String>,
}

pub async fn list_stations(
    State(state): State<AppState>,
    Query(query): Query<ListStationQuery>,
) -> Result<impl IntoResponse, ApiErr> {
    query.validate()?;
    let stations =
        station_service::list_stations(&state.platform.pool, query.line_code.as_deref()).await?;
    Ok(Json(stations))
}

pub async fn get_station(
    State(state): State<AppState>,
    Path(station_id): Path<Uuid>,
) -> Result<impl IntoResponse, ApiErr> {
    let station = station_service::get_station_by_id(&state.platform.pool, station_id)
        .await?
        .ok_or_else(|| ApiErr::NotFound("Station not found".to_string(), None))?;
    let signals = station_service::list_station_signals(&state.platform.pool, station_id).await?;
    Ok(Json(json!({
        "station": station,
        "signals": signals,
    })))
}

#[derive(Debug, Deserialize, Validate)]
pub struct CreateStationReq {
    #[validate(length(min = 1, max = 100))]
    pub code: String,
    #[validate(length(min = 1, max = 100))]
    pub name: String,
    #[validate(length(min = 1, max = 50))]
    pub line_code: Option<String>,
    #[validate(length(min = 1, max = 50))]
    pub segment_code: Option<String>,
    #[validate(length(min = 1, max = 32))]
    pub station_type: String,
    pub enabled: Option<bool>,
    pub description: Option<String>,
}

pub async fn create_station(
    State(state): State<AppState>,
    Json(payload): Json<CreateStationReq>,
) -> Result<impl IntoResponse, ApiErr> {
    payload.validate()?;
    validate_station_type(&payload.station_type)?;

    if station_service::get_station_by_code(&state.platform.pool, &payload.code)
        .await?
        .is_some()
    {
        return Err(ApiErr::BadRequest(
            "Station code already exists".to_string(),
            None,
        ));
    }

    let station_id = station_service::create_station(
        &state.platform.pool,
        station_service::CreateStationParams {
            code: &payload.code,
            name: &payload.name,
            line_code: payload.line_code.as_deref(),
            segment_code: payload.segment_code.as_deref(),
            station_type: &payload.station_type,
            enabled: payload.enabled.unwrap_or(true),
            description: payload.description.as_deref(),
        },
    )
    .await?;

    Ok((
        StatusCode::CREATED,
        Json(json!({ "id": station_id, "ok_msg": "Station created" })),
    ))
}

#[derive(Debug, Deserialize, Validate)]
pub struct UpdateStationReq {
    #[validate(length(min = 1, max = 100))]
    pub code: Option<String>,
    #[validate(length(min = 1, max = 100))]
    pub name: Option<String>,
    #[validate(length(min = 1, max = 50))]
    pub line_code: Option<String>,
    #[validate(length(min = 1, max = 50))]
    pub segment_code: Option<String>,
    #[validate(length(min = 1, max = 32))]
    pub station_type: Option<String>,
    pub enabled: Option<bool>,
    pub description: Option<String>,
}

pub async fn update_station(
    State(state): State<AppState>,
    Path(station_id): Path<Uuid>,
    Json(payload): Json<UpdateStationReq>,
) -> Result<impl IntoResponse, ApiErr> {
    payload.validate()?;
    if let Some(t) = payload.station_type.as_deref() {
        validate_station_type(t)?;
    }

    let existing = station_service::get_station_by_id(&state.platform.pool, station_id)
        .await?
        .ok_or_else(|| ApiErr::NotFound("Station not found".to_string(), None))?;

    if let Some(code) = payload.code.as_deref() {
        if let Some(other) =
            station_service::get_station_by_code(&state.platform.pool, code).await?
        {
            if other.id != existing.id {
                return Err(ApiErr::BadRequest(
                    "Station code already exists".to_string(),
                    None,
                ));
            }
        }
    }

    station_service::update_station(
        &state.platform.pool,
        station_id,
        station_service::UpdateStationParams {
            code: payload.code.as_deref(),
            name: payload.name.as_deref(),
            line_code: payload.line_code.as_deref(),
            segment_code: payload.segment_code.as_deref(),
            station_type: payload.station_type.as_deref(),
            enabled: payload.enabled,
            description: payload.description.as_deref(),
        },
    )
    .await?;

    Ok(Json(json!({ "ok_msg": "Station updated" })))
}

pub async fn delete_station(
    State(state): State<AppState>,
    Path(station_id): Path<Uuid>,
) -> Result<impl IntoResponse, ApiErr> {
    let deleted = station_service::delete_station(&state.platform.pool, station_id).await?;
    if !deleted {
        return Err(ApiErr::NotFound("Station not found".to_string(), None));
    }
    Ok(StatusCode::NO_CONTENT)
}

#[derive(Debug, Deserialize, Validate)]
pub struct UpsertStationSignalReq {
    #[validate(length(min = 1, max = 32))]
    pub signal_role: String,
    pub point_id: Option<Uuid>,
    #[validate(length(min = 1, max = 32))]
    pub derived_from_role: Option<String>,
    pub invert_value: Option<bool>,
}

pub async fn upsert_station_signal(
    State(state): State<AppState>,
    Path(station_id): Path<Uuid>,
    Json(payload): Json<UpsertStationSignalReq>,
) -> Result<impl IntoResponse, ApiErr> {
    payload.validate()?;
    validate_signal_role(&payload.signal_role)?;
    if let Some(role) = payload.derived_from_role.as_deref() {
        validate_signal_role(role)?;
    }
    if payload.point_id.is_none() && payload.derived_from_role.is_none() {
        return Err(ApiErr::BadRequest(
            "either point_id or derived_from_role must be provided".to_string(),
            None,
        ));
    }

    station_service::get_station_by_id(&state.platform.pool, station_id)
        .await?
        .ok_or_else(|| ApiErr::NotFound("Station not found".to_string(), None))?;

    let signal = station_service::upsert_station_signal(
        &state.platform.pool,
        station_id,
        station_service::UpsertStationSignalParams {
            signal_role: payload.signal_role,
            point_id: payload.point_id,
            derived_from_role: payload.derived_from_role,
            invert_value: payload.invert_value.unwrap_or(false),
        },
    )
    .await?;

    Ok(Json(signal))
}

pub async fn delete_station_signal(
    State(state): State<AppState>,
    Path((station_id, role)): Path<(Uuid, String)>,
) -> Result<impl IntoResponse, ApiErr> {
    validate_signal_role(&role)?;
    let deleted =
        station_service::delete_station_signal(&state.platform.pool, station_id, &role).await?;
    if !deleted {
        return Err(ApiErr::NotFound(
            "Station signal binding not found".to_string(),
            None,
        ));
    }
    Ok(StatusCode::NO_CONTENT)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::model::StationSignalRole;

    #[test]
    fn create_station_req_rejects_blank_code() {
        let payload = CreateStationReq {
            code: "".to_string(),
            name: "Dry-1 In".to_string(),
            line_code: None,
            segment_code: None,
            station_type: "dry_in".to_string(),
            enabled: None,
            description: None,
        };
        assert!(payload.validate().is_err());
    }

    #[test]
    fn validate_station_type_rejects_unknown() {
        assert!(validate_station_type("nope").is_err());
        assert!(validate_station_type("dry_in").is_ok());
    }

    #[test]
    fn station_signal_role_enum_covers_handler_allowlist() {
        let known = [
            StationSignalRole::Presence,
            StationSignalRole::Vacancy,
            StationSignalRole::Arrived,
            StationSignalRole::AllowIn,
            StationSignalRole::Done,
            StationSignalRole::Fault,
        ];
        for role in known {
            assert!(SIGNAL_ROLES.contains(&role.as_str()));
        }
    }
}