//! HTTP handlers for the `user_ai_prefs` settings surface.
//!
//! `GET /prefs` — the current row (or the empty shape when none exists).
//! `PUT /prefs` — partial update: an omitted field is unchanged, an explicit
//! null clears, a value sets. `display_tz` is validated against chrono-tz
//! (the same check as `camera_tz::display_zone_for`); an invalid zone name
//! → 400 and nothing is written.
//! `GET /timezones` — the IANA zone list from chrono-tz, for picker UIs
//! (unauthenticated; static data).
//!
//! Scope: existing columns only (voice, library, display_tz) — no migration.
//! The legacy `tz_offset_minutes` column is preserved verbatim on every
//! write. `POST /reels`'s `capture_prefs` stays as the incidental writer;
//! both writers hit the same single row, so they're idempotent. Owner
//! defaults (model/backend/persona/reels) are a separate follow-on ticket
//! that adds the columns.

use actix_web::{HttpResponse, web};
use chrono_tz::Tz;
use serde::{Deserialize, Serialize};
use serde_json::json;
use std::str::FromStr;
use std::time::{SystemTime, UNIX_EPOCH};

use crate::data::Claims;
use crate::database::models::{UpsertUserAiPrefs, UserAiPrefs};
use crate::state::AppState;

// ---------------------------------------------------------------------------
// Wire shapes — snake_case, matching the `display_tz` contract surface.
// ---------------------------------------------------------------------------

#[derive(Serialize, Deserialize, Debug)]
pub struct PrefsResponse {
    pub voice: Option<String>,
    pub library: Option<String>,
    pub display_tz: Option<String>,
    pub updated_at: Option<i64>,
}

/// One partial-update field. `Absent` = key omitted (unchanged), `Null` =
/// explicit JSON null (clear), `Val(v)` = set. serde's derive can't keep
/// explicit null and a missing key apart on `Option<Option<T>>` (both come
/// out as outer `None`), so this carries a hand-rolled visitor.
#[derive(Clone, Debug, Default)]
pub enum TriState {
    #[default]
    Absent,
    Null,
    Val(String),
}

impl<'de> Deserialize<'de> for TriState {
    fn deserialize<D>(deserializer: D) -> Result<TriState, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        struct Visitor;
        impl<'de> serde::de::Visitor<'de> for Visitor {
            type Value = TriState;
            fn expecting(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
                f.write_str("a string or null")
            }
            // serde_json routes an explicit JSON null to visit_unit/visit_none;
            // a missing key never calls deserialize — `#[serde(default)]`
            // supplies Absent instead.
            fn visit_unit<E: serde::de::Error>(self) -> Result<TriState, E> {
                Ok(TriState::Null)
            }
            fn visit_none<E: serde::de::Error>(self) -> Result<TriState, E> {
                Ok(TriState::Null)
            }
            fn visit_str<E: serde::de::Error>(self, v: &str) -> Result<TriState, E> {
                Ok(TriState::Val(v.to_string()))
            }
            fn visit_string<E: serde::de::Error>(self, v: String) -> Result<TriState, E> {
                Ok(TriState::Val(v))
            }
        }
        deserializer.deserialize_any(Visitor)
    }
}

/// Partial update: an omitted field is unchanged, an explicit null clears,
/// a value sets.
#[derive(Deserialize, Debug, Default)]
pub struct UpdatePrefsRequest {
    #[serde(default)]
    pub voice: TriState,
    #[serde(default)]
    pub library: TriState,
    #[serde(default)]
    pub display_tz: TriState,
}

#[derive(Serialize, Debug)]
pub struct TimezonesResponse {
    pub timezones: Vec<String>,
}

// ---------------------------------------------------------------------------
// Pure seams
// ---------------------------------------------------------------------------

/// The same zone-name check as `camera_tz::display_zone_for` (trim, then
/// chrono-tz parse). Used to reject writes with an unparseable zone before
/// any DB touch.
fn is_valid_display_tz(name: &str) -> bool {
    Tz::from_str(name.trim()).is_ok()
}

/// The full set of zone names `PUT /prefs` will accept — `chrono_tz::TZ_VARIANTS`
/// is exactly the domain of `Tz::from_str`, so the picker list and the
/// validation check can never drift apart.
pub fn all_timezones() -> Vec<String> {
    chrono_tz::TZ_VARIANTS
        .iter()
        .map(|tz| tz.to_string())
        .collect()
}

/// Merge a partial update onto the existing row. Returns
/// `(voice, library, display_tz, changed)`. An omitted field keeps the
/// stored value (or `None` when there is no row); a present field wins.
fn tri_value(
    field: &TriState,
    existing: Option<&UserAiPrefs>,
    keep: impl FnOnce(&UserAiPrefs) -> Option<String>,
) -> Option<String> {
    match field {
        TriState::Absent => existing.and_then(keep),
        TriState::Null => None,
        TriState::Val(v) => Some(v.clone()),
    }
}

fn merge_patch(
    existing: Option<&UserAiPrefs>,
    patch: &UpdatePrefsRequest,
) -> (Option<String>, Option<String>, Option<String>, bool) {
    let voice = tri_value(&patch.voice, existing, |e| e.voice.clone());
    let library = tri_value(&patch.library, existing, |e| e.library.clone());
    let display_tz = tri_value(&patch.display_tz, existing, |e| e.display_tz.clone());
    let changed = !matches!(patch.voice, TriState::Absent)
        || !matches!(patch.library, TriState::Absent)
        || !matches!(patch.display_tz, TriState::Absent);
    (voice, library, display_tz, changed)
}

fn row_to_response(row: Option<&UserAiPrefs>) -> PrefsResponse {
    match row {
        Some(row) => PrefsResponse {
            voice: row.voice.clone(),
            library: row.library.clone(),
            display_tz: row.display_tz.clone(),
            updated_at: Some(row.updated_at),
        },
        None => PrefsResponse {
            voice: None,
            library: None,
            display_tz: None,
            updated_at: None,
        },
    }
}

// ---------------------------------------------------------------------------
// Handlers
// ---------------------------------------------------------------------------

pub async fn get_prefs(_claims: Claims, app_state: web::Data<AppState>) -> HttpResponse {
    let mut dao = match app_state.user_ai_prefs_dao.lock() {
        Ok(dao) => dao,
        Err(_) => {
            return HttpResponse::InternalServerError().json(json!({
                "error": "prefs store unavailable"
            }));
        }
    };
    match dao.get_prefs(&opentelemetry::Context::new()) {
        Ok(row) => HttpResponse::Ok().json(row_to_response(row.as_ref())),
        Err(e) => HttpResponse::InternalServerError().json(json!({
            "error": format!("failed to read prefs: {e}")
        })),
    }
}

pub async fn put_prefs(
    _claims: Claims,
    body: web::Json<UpdatePrefsRequest>,
    app_state: web::Data<AppState>,
) -> HttpResponse {
    let patch = body.0;

    // Validate before any write: an invalid zone name → 400, nothing written.
    if let TriState::Val(name) = &patch.display_tz
        && !is_valid_display_tz(name)
    {
        return HttpResponse::BadRequest().json(json!({
            "error": format!("invalid display_tz: {name}")
        }));
    }

    let mut dao = match app_state.user_ai_prefs_dao.lock() {
        Ok(dao) => dao,
        Err(_) => {
            return HttpResponse::InternalServerError().json(json!({
                "error": "prefs store unavailable"
            }));
        }
    };
    let ctx = opentelemetry::Context::new();
    let existing = match dao.get_prefs(&ctx) {
        Ok(row) => row,
        Err(e) => {
            return HttpResponse::InternalServerError().json(json!({
                "error": format!("failed to read prefs: {e}")
            }));
        }
    };

    let (voice, library, display_tz, changed) = merge_patch(existing.as_ref(), &patch);
    if !changed {
        // Empty body: no-op, return the current row without bumping updated_at.
        return HttpResponse::Ok().json(row_to_response(existing.as_ref()));
    }

    let now = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .expect("Time went backwards")
        .as_secs() as i64;

    let resp = PrefsResponse {
        voice: voice.clone(),
        library: library.clone(),
        display_tz: display_tz.clone(),
        updated_at: Some(now),
    };
    let upsert = UpsertUserAiPrefs {
        voice,
        // Frozen legacy column: preserved verbatim, never written by this
        // surface.
        tz_offset_minutes: existing.as_ref().and_then(|e| e.tz_offset_minutes),
        library,
        display_tz,
        updated_at: now,
    };
    match dao.upsert_prefs(&ctx, &upsert) {
        Ok(()) => HttpResponse::Ok().json(resp),
        Err(e) => HttpResponse::InternalServerError().json(json!({
            "error": format!("failed to write prefs: {e}")
        })),
    }
}

pub async fn list_timezones() -> HttpResponse {
    HttpResponse::Ok().json(TimezonesResponse {
        timezones: all_timezones(),
    })
}

#[cfg(test)]
mod tests {
    use super::*;
    use actix_web::App;
    use actix_web::test::{TestRequest, call_service, init_service, read_body_json};
    use std::sync::{Arc, Mutex};

    use crate::database::{SqliteUserAiPrefsDao, UserAiPrefsDao};

    /// AppState whose prefs DAO shares one in-memory connection, plus a
    /// second DAO handle on the same connection for seeding.
    fn prefs_state() -> (web::Data<AppState>, SqliteUserAiPrefsDao) {
        let conn = Arc::new(Mutex::new(crate::database::test::in_memory_db_connection()));
        let mut state = AppState::test_state();
        let state_dao: Arc<Mutex<Box<dyn UserAiPrefsDao>>> = Arc::new(Mutex::new(Box::new(
            SqliteUserAiPrefsDao::from_connection(conn.clone()),
        )));
        state.user_ai_prefs_dao = state_dao;
        let seed_dao = SqliteUserAiPrefsDao::from_connection(conn);
        (web::Data::new(state), seed_dao)
    }

    fn make_token() -> String {
        let claims = Claims::valid_user(String::from("1"));
        jsonwebtoken::encode(
            &jsonwebtoken::Header::default(),
            &claims,
            &jsonwebtoken::EncodingKey::from_secret(b"test_key"),
        )
        .unwrap()
    }

    fn auth() -> (&'static str, String) {
        ("Authorization", format!("Bearer {}", make_token()))
    }

    fn seed(dao: &mut SqliteUserAiPrefsDao, row: UpsertUserAiPrefs) {
        dao.upsert_prefs(&opentelemetry::Context::new(), &row)
            .expect("seed prefs");
    }

    fn seeded_row(
        voice: Option<&str>,
        library: Option<&str>,
        display_tz: Option<&str>,
    ) -> UpsertUserAiPrefs {
        UpsertUserAiPrefs {
            voice: voice.map(str::to_string),
            tz_offset_minutes: Some(-240),
            library: library.map(str::to_string),
            updated_at: 1_700_000_000,
            display_tz: display_tz.map(str::to_string),
        }
    }

    // --- GET /prefs ---------------------------------------------------------

    #[actix_rt::test]
    async fn get_prefs_requires_auth() {
        let (state, _seed) = prefs_state();
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let req = TestRequest::get().uri("/prefs").to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 401);
    }

    #[actix_rt::test]
    async fn get_prefs_returns_empty_shape_when_no_row() {
        let (state, _seed) = prefs_state();
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let (header, value) = auth();
        let req = TestRequest::get()
            .uri("/prefs")
            .insert_header((header, value))
            .to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 200);
        let body: serde_json::Value = read_body_json(resp).await;
        assert_eq!(
            body,
            serde_json::json!({
                "voice": null,
                "library": null,
                "display_tz": null,
                "updated_at": null
            })
        );
    }

    #[actix_rt::test]
    async fn get_prefs_returns_stored_row() {
        let (state, mut seed_dao) = prefs_state();
        seed(
            &mut seed_dao,
            seeded_row(Some("grandma"), Some("2"), Some("America/New_York")),
        );
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let (header, value) = auth();
        let req = TestRequest::get()
            .uri("/prefs")
            .insert_header((header, value))
            .to_request();
        let resp = call_service(&app, req).await;
        let body: serde_json::Value = read_body_json(resp).await;
        assert_eq!(body["voice"], "grandma");
        assert_eq!(body["library"], "2");
        assert_eq!(body["display_tz"], "America/New_York");
        assert_eq!(body["updated_at"], 1_700_000_000);
    }

    // --- PUT /prefs ---------------------------------------------------------

    #[actix_rt::test]
    async fn put_prefs_requires_auth() {
        let (state, _seed) = prefs_state();
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let req = TestRequest::put()
            .uri("/prefs")
            .set_json(serde_json::json!({"voice": "dad"}))
            .to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 401);
    }

    #[actix_rt::test]
    async fn put_prefs_partial_update_leaves_omitted_fields_untouched() {
        let (state, mut seed_dao) = prefs_state();
        seed(
            &mut seed_dao,
            seeded_row(Some("grandma"), Some("1"), Some("America/New_York")),
        );
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let (header, value) = auth();
        let req = TestRequest::put()
            .uri("/prefs")
            .insert_header((header, value))
            .set_json(serde_json::json!({"voice": "dad"}))
            .to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 200);

        let mut dao = state.user_ai_prefs_dao.lock().unwrap();
        let row = dao
            .get_prefs(&opentelemetry::Context::new())
            .unwrap()
            .unwrap();
        assert_eq!(row.voice.as_deref(), Some("dad"));
        assert_eq!(row.library.as_deref(), Some("1"));
        assert_eq!(row.display_tz.as_deref(), Some("America/New_York"));
        // The frozen legacy column survives the write.
        assert_eq!(row.tz_offset_minutes, Some(-240));
        assert!(row.updated_at > 1_700_000_000);
    }

    #[actix_rt::test]
    async fn put_prefs_explicit_null_clears_field() {
        let (state, mut seed_dao) = prefs_state();
        seed(
            &mut seed_dao,
            seeded_row(Some("grandma"), Some("1"), Some("America/New_York")),
        );
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let (header, value) = auth();
        let req = TestRequest::put()
            .uri("/prefs")
            .insert_header((header, value))
            .set_json(serde_json::json!({"voice": null}))
            .to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 200);

        let mut dao = state.user_ai_prefs_dao.lock().unwrap();
        let row = dao
            .get_prefs(&opentelemetry::Context::new())
            .unwrap()
            .unwrap();
        assert!(row.voice.is_none());
        assert_eq!(row.library.as_deref(), Some("1"));
        assert_eq!(row.display_tz.as_deref(), Some("America/New_York"));
    }

    #[actix_rt::test]
    async fn put_prefs_inserts_row_when_none_exists() {
        let (state, _seed) = prefs_state();
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let (header, value) = auth();
        let req = TestRequest::put()
            .uri("/prefs")
            .insert_header((header, value))
            .set_json(serde_json::json!({"library": "1"}))
            .to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 200);

        let mut dao = state.user_ai_prefs_dao.lock().unwrap();
        let row = dao
            .get_prefs(&opentelemetry::Context::new())
            .unwrap()
            .unwrap();
        assert_eq!(row.library.as_deref(), Some("1"));
        assert!(row.voice.is_none());
        assert!(row.display_tz.is_none());
    }

    #[actix_rt::test]
    async fn put_prefs_invalid_display_tz_returns_400_and_writes_nothing() {
        let (state, mut seed_dao) = prefs_state();
        seed(
            &mut seed_dao,
            seeded_row(Some("grandma"), Some("1"), Some("America/New_York")),
        );
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let (header, value) = auth();
        let req = TestRequest::put()
            .uri("/prefs")
            .insert_header((header, value))
            .set_json(serde_json::json!({"voice": "dad", "display_tz": "Not/A_Zone"}))
            .to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 400);

        // Nothing written — not even the valid field in the same body.
        let mut dao = state.user_ai_prefs_dao.lock().unwrap();
        let row = dao
            .get_prefs(&opentelemetry::Context::new())
            .unwrap()
            .unwrap();
        assert_eq!(row.voice.as_deref(), Some("grandma"));
        assert_eq!(row.display_tz.as_deref(), Some("America/New_York"));
        assert_eq!(row.updated_at, 1_700_000_000);
    }

    #[actix_rt::test]
    async fn put_prefs_valid_display_tz_persists() {
        let (state, _seed) = prefs_state();
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let (header, value) = auth();
        let req = TestRequest::put()
            .uri("/prefs")
            .insert_header((header, value))
            .set_json(serde_json::json!({"display_tz": "Europe/Berlin"}))
            .to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 200);

        let mut dao = state.user_ai_prefs_dao.lock().unwrap();
        let row = dao
            .get_prefs(&opentelemetry::Context::new())
            .unwrap()
            .unwrap();
        assert_eq!(row.display_tz.as_deref(), Some("Europe/Berlin"));
    }

    #[actix_rt::test]
    async fn put_prefs_empty_body_is_noop() {
        let (state, _seed) = prefs_state();
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let (header, value) = auth();
        let req = TestRequest::put()
            .uri("/prefs")
            .insert_header((header, value))
            .set_json(serde_json::json!({}))
            .to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 200);
        let body: serde_json::Value = read_body_json(resp).await;
        assert_eq!(body["updated_at"], serde_json::Value::Null);

        let mut dao = state.user_ai_prefs_dao.lock().unwrap();
        assert!(
            dao.get_prefs(&opentelemetry::Context::new())
                .unwrap()
                .is_none()
        );
    }

    // --- GET /timezones -----------------------------------------------------

    #[actix_rt::test]
    async fn list_timezones_is_unauthenticated_and_includes_iana_zones() {
        let (state, _seed) = prefs_state();
        let app = init_service(
            App::new()
                .service(
                    web::resource("/prefs")
                        .route(web::get().to(get_prefs))
                        .route(web::put().to(put_prefs)),
                )
                .service(web::resource("/timezones").route(web::get().to(list_timezones)))
                .app_data(state.clone()),
        )
        .await;
        let req = TestRequest::get().uri("/timezones").to_request();
        let resp = call_service(&app, req).await;
        assert_eq!(resp.status(), 200);
        let body: serde_json::Value = read_body_json(resp).await;
        let zones: Vec<&str> = body["timezones"]
            .as_array()
            .expect("timezones is an array")
            .iter()
            .map(|v| v.as_str().expect("zone is a string"))
            .collect();
        assert!(
            zones.contains(&"America/New_York"),
            "IANA list must include America/New_York"
        );
        assert!(zones.len() > 400, "IANA list looks truncated");
    }

    #[test]
    fn all_timezones_is_exactly_the_from_str_domain() {
        // The picker list and the PUT /prefs validation must never drift:
        // every listed name parses, and the list is the full variant set.
        let zones = all_timezones();
        assert_eq!(zones.len(), chrono_tz::TZ_VARIANTS.len());
        for z in &zones {
            assert!(Tz::from_str(z).is_ok(), "listed zone must parse: {z}");
        }
        assert!(zones.contains(&"America/New_York".to_string()));
    }

    // --- merge_patch (pure) --------------------------------------------------

    #[test]
    fn merge_patch_omitted_keeps_existing() {
        let row = UserAiPrefs {
            id: 1,
            voice: Some("a".into()),
            tz_offset_minutes: None,
            library: Some("b".into()),
            updated_at: 0,
            display_tz: Some("c".into()),
        };
        let (voice, library, display_tz, changed) =
            merge_patch(Some(&row), &UpdatePrefsRequest::default());
        assert_eq!(voice.as_deref(), Some("a"));
        assert_eq!(library.as_deref(), Some("b"));
        assert_eq!(display_tz.as_deref(), Some("c"));
        assert!(!changed);
    }

    #[test]
    fn merge_patch_present_field_wins_including_null() {
        let row = UserAiPrefs {
            id: 1,
            voice: Some("a".into()),
            tz_offset_minutes: None,
            library: None,
            updated_at: 0,
            display_tz: None,
        };
        let patch = UpdatePrefsRequest {
            voice: TriState::Null,                     // clear
            library: TriState::Val(String::from("x")), // set
            display_tz: TriState::Absent,
        };
        let (voice, library, display_tz, changed) = merge_patch(Some(&row), &patch);
        assert!(voice.is_none());
        assert_eq!(library.as_deref(), Some("x"));
        assert!(display_tz.is_none());
        assert!(changed);
    }
}