//! Durable, queryable storage for submitted answers - the KV-backed
//! counterpart to the ephemeral `events::AnswerSubmitted` every
//! submission already publishes. The runtime here has no notion of
//! "applicant" or any other specific workflow: an `Alternative.record_as`
//! names a NATS KV bucket (nothing more); on submit, the response gets
//! wrapped in the same envelope (`Answer`) regardless of what content
//! produced it. `resource::get_resource` reads it back generically, and
//! `transition_answer` below moves an answer between states named in
//! content (`ResourceSpec.transitions`), never states hardcoded here.
//! Whatever workflow this ends up powering - applicant review, order
//! triage, comment moderation - is entirely a property of some
//! `portal-content` YAML, not of this file.

use leptos::prelude::*;
use serde::{Deserialize, Serialize};

/// An answer's starting state - content decides what it may transition
/// to (`ResourceSpec.transitions`), never this file.
pub const OPEN_STATE: &str = "open";

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct Answer {
    /// The submission's chain hash - stable, unique, and already what
    /// ties this answer back into the DAG a transition later extends.
    pub id: String,
    pub question_id: String,
    pub alternative: String,
    /// The submitted form fields, verbatim - the runtime never inspects
    /// these keys, only content (via its own copy/labels) gives them
    /// meaning.
    pub responses: serde_json::Value,
    pub state: String,
    pub submitted_ms: i64,
    #[serde(default)]
    pub decided_ms: Option<i64>,
    #[serde(default)]
    pub decided_by: Option<String>,
}

/// Writes a submitted answer into `bucket`, creating it on first use -
/// there's no fixed, pre-declared list of buckets, since content can
/// name any.
#[cfg(feature = "ssr")]
pub async fn store_answer(
    js: &async_nats::jetstream::Context,
    bucket: &str,
    id: String,
    question_id: &str,
    alternative: &str,
    responses: &serde_json::Value,
    submitted_ms: i64,
) -> anyhow::Result<()> {
    let store = match js.get_key_value(bucket).await {
        Ok(store) => store,
        Err(_) => {
            js.create_key_value(async_nats::jetstream::kv::Config {
                bucket: bucket.to_string(),
                ..Default::default()
            })
            .await?
        }
    };
    let answer = Answer {
        id: id.clone(),
        question_id: question_id.to_string(),
        alternative: alternative.to_string(),
        responses: responses.clone(),
        state: OPEN_STATE.to_string(),
        submitted_ms,
        decided_ms: None,
        decided_by: None,
    };
    let data = serde_json::to_vec(&answer)?;
    store.put(id, data.into()).await?;
    Ok(())
}

/// Moves a stored answer from `open` to one of the target states its
/// own resource spec declares (`ResourceSpec.transitions`) - `to` is
/// checked against that content-declared allow-list, never accepted as
/// an arbitrary string. Requires a signed-in member of the resource's
/// `requires_group`, regardless of whether the resource is otherwise
/// `public` - reads can be public, mutations always need identity.
#[server]
pub async fn transition_answer(
    question_id: String,
    feature_name: String,
    item_id: String,
    to: String,
) -> Result<(), ServerFnError> {
    use crate::auth::{User, SESSION_USER_KEY};
    use crate::chain::hash_node;
    use crate::events::{emit_answer_submitted, AnswerSubmitted};
    use crate::server::AppState;

    let state = expect_context::<AppState>();
    let question = state
        .questions
        .load()
        .get(&question_id)
        .cloned()
        .ok_or_else(|| ServerFnError::new("unknown question"))?;
    let feature = question
        .alternatives
        .iter()
        .flat_map(|a| &a.features)
        .find(|f| f.name == feature_name)
        .ok_or_else(|| ServerFnError::new("unknown feature"))?;
    let resource = feature
        .resource
        .as_ref()
        .ok_or_else(|| ServerFnError::new("feature has no resource"))?;
    let transition = resource
        .transitions
        .iter()
        .find(|t| t.to == to)
        .ok_or_else(|| ServerFnError::new("no such transition"))?
        .clone();
    let group = resource
        .requires_group
        .as_deref()
        .ok_or_else(|| ServerFnError::new("resource has no transitions available"))?;

    let session: tower_sessions::Session = leptos_axum::extract().await?;
    let user = session
        .get::<User>(SESSION_USER_KEY)
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))?
        .ok_or_else(|| ServerFnError::new("not signed in"))?;
    if !user.groups.iter().any(|g| g == group) {
        return Err(ServerFnError::new("not authorized"));
    }

    let store = state
        .jetstream
        .get_key_value(&resource.bucket)
        .await
        .map_err(|e| ServerFnError::new(format!("resource bucket unavailable: {e}")))?;
    let bytes = store
        .get(&item_id)
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))?
        .ok_or_else(|| ServerFnError::new("unknown answer"))?;
    let mut answer: Answer =
        serde_json::from_slice(&bytes).map_err(|e| ServerFnError::new(e.to_string()))?;
    if answer.state != OPEN_STATE {
        return Err(ServerFnError::new("already decided"));
    }

    let decided_ms = chrono::Utc::now().timestamp_millis();
    answer.state = to.clone();
    answer.decided_ms = Some(decided_ms);
    answer.decided_by = Some(user.username.clone());

    let data = serde_json::to_vec(&answer).map_err(|e| ServerFnError::new(e.to_string()))?;
    store
        .put(&item_id, data.into())
        .await
        .map_err(|e| ServerFnError::new(e.to_string()))?;

    // Extend the DAG: the decision is a child node of the answer's own
    // submission hash, published the same way any other answer is -
    // question_id/alternative come from this call's own arguments and
    // the content-declared transition label, never a hardcoded value.
    let decision_payload = serde_json::json!({ "to": to, "item": item_id, "by": user.username });
    let parent_hashes = vec![item_id.clone()];
    let chain_hash = hash_node(&question_id, &parent_hashes, &decision_payload, decided_ms);
    let event = AnswerSubmitted {
        chain_hash,
        parent_hashes,
        question_id,
        alternative: transition.label,
        responses: decision_payload,
        timestamp_ms: decided_ms,
    };
    emit_answer_submitted(&state.nats, &event)
        .await
        .map_err(|e| ServerFnError::new(format!("nats publish failed: {e}")))?;

    Ok(())
}