//! /v1/validate — gateway-side artifact validation endpoint.
//!
//! Phase 43 v3 part 2: makes the validator crate network-callable.
//! Any caller (scrum loop, test harness, future agent) can POST a
//! generated artifact and get back a Report (success) or
//! ValidationError (failure with structured field/reason).
//!
//! Request shape:
//!   POST /v1/validate
//!   {
//!     "kind": "fill" | "email" | "playbook",
//!     "artifact": { ... },
//!     "context": { ... }   // optional — folded into artifact._context
//!   }
//!
//! Response on success: 200 + Report JSON
//! Response on failure: 422 + ValidationError JSON
//! Response on bad request: 400 + plain-text error
//!
//! The shared WorkerLookup is loaded once at gateway startup from
//! workers_500k.parquet (path configurable via LH_WORKERS_PARQUET
//! env, defaults to data/datasets/workers_500k.parquet). Falls back
//! to an empty InMemoryWorkerLookup if the file is missing — the
//! validators will still run schema/length/PII checks but worker-
//! existence checks will all fail (Consistency error), which is the
//! correct behavior when the roster isn't configured.

use axum::{extract::State, http::StatusCode, response::IntoResponse, Json};
use serde::Deserialize;
use validator::{
    Artifact, Validator, ValidationError,
    staffing::{
        fill::FillValidator,
        email::EmailValidator,
        playbook::PlaybookValidator,
    },
};

#[derive(Deserialize)]
pub struct ValidateRequest {
    /// `"fill" | "email" | "playbook"` — picks which validator runs.
    pub kind: String,
    /// The artifact JSON (free-form; shape depends on `kind`).
    pub artifact: serde_json::Value,
    /// Optional context bag — merged into `artifact._context` so the
    /// validator can read fields like `target_count`, `city`,
    /// `client_id`, `candidate_id` without callers having to embed
    /// `_context` in the artifact themselves.
    #[serde(default)]
    pub context: Option<serde_json::Value>,
}

pub async fn validate(
    State(state): State<super::V1State>,
    Json(req): Json<ValidateRequest>,
) -> impl IntoResponse {
    // Merge context into artifact under `_context` so validators can
    // pull contract metadata uniformly.
    let mut artifact_value = req.artifact;
    if let Some(ctx) = req.context {
        if let Some(obj) = artifact_value.as_object_mut() {
            obj.insert("_context".to_string(), ctx);
        }
    }

    // Dispatch.
    let workers = state.validate_workers.clone();
    let result: Result<validator::Report, ValidationError> = match req.kind.as_str() {
        "fill" => FillValidator::new(workers).validate(&Artifact::FillProposal(artifact_value)),
        "email" => EmailValidator::new(workers).validate(&Artifact::EmailDraft(artifact_value)),
        "playbook" => PlaybookValidator.validate(&Artifact::Playbook(artifact_value)),
        other => return (
            StatusCode::BAD_REQUEST,
            format!("unknown kind '{other}' — expected fill | email | playbook"),
        ).into_response(),
    };

    match result {
        Ok(report) => (StatusCode::OK, Json(report)).into_response(),
        Err(e) => (StatusCode::UNPROCESSABLE_ENTITY, Json(e)).into_response(),
    }
}