//! PresenceStatus/* method handlers (JMAP Chat extension §PresenceStatus).
//!
//! PresenceStatus is a singleton — exactly one per account. Clients MUST NOT
//! create or destroy it; any attempt is rejected with `forbidden`. Only
//! `update` is permitted. `id` and `updatedAt` are server-set: `id` is
//! immutable and `updatedAt` is injected by the handler on every update.

use jmap_chat_types::PresenceStatus;
use jmap_types::{Id, Invocation, JmapError, State};
use serde_json::{json, Value};

use crate::backend::{BackendSetError, ChatBackend, SetError, SetErrorType};
use crate::helpers::{extract_account_id, not_found_json, now_utc_string, ser, set_error_value};

// ---------------------------------------------------------------------------
// PresenceStatus/get
// ---------------------------------------------------------------------------

/// Handle a `PresenceStatus/get` method call.
pub async fn handle_presence_get<B: ChatBackend>(
    backend: &B,
    args: Value,
) -> Result<(Value, Vec<Invocation>), JmapError> {
    let account_id = extract_account_id(&args)?;

    let Value::Object(mut args) = args else {
        return Err(JmapError::invalid_arguments(
            "arguments must be a JSON object",
        ));
    };

    let ids: Option<Vec<Id>> = match args.remove("ids").unwrap_or(Value::Null) {
        Value::Null => None,
        v => Some(
            serde_json::from_value(v)
                .map_err(|_| JmapError::invalid_arguments("ids must be an Id array"))?,
        ),
    };

    let ids_slice = ids.as_deref();
    let (list, not_found) = backend
        .get_objects::<PresenceStatus>(&account_id, ids_slice, None)
        .await
        .map_err(|e| JmapError::server_fail(e.to_string()))?;

    let state = backend
        .get_state::<PresenceStatus>(&account_id)
        .await
        .map_err(|e| JmapError::server_fail(e.to_string()))?;

    let list_json: Vec<Value> = list.iter().map(ser).collect::<Result<Vec<_>, _>>()?;

    Ok((
        json!({
            "accountId": account_id.as_ref(),
            "state": state.as_ref(),
            "list": list_json,
            "notFound": not_found_json(&not_found),
        }),
        vec![],
    ))
}

// ---------------------------------------------------------------------------
// PresenceStatus/changes
// ---------------------------------------------------------------------------

/// Handle a `PresenceStatus/changes` method call (RFC 8620 §5.2).
pub async fn handle_presence_changes<B: ChatBackend>(
    backend: &B,
    args: Value,
) -> Result<(Value, Vec<Invocation>), JmapError> {
    let account_id = extract_account_id(&args)?;

    let since_state: State = match args.get("sinceState").and_then(|v| v.as_str()) {
        Some(s) => State::from(s),
        None => return Err(JmapError::invalid_arguments("sinceState is required")),
    };

    let max_changes: Option<u64> = match args.get("maxChanges") {
        None | Some(Value::Null) => None,
        Some(v) => Some(v.as_u64().filter(|&n| n > 0).ok_or_else(|| {
            JmapError::invalid_arguments("maxChanges must be a positive integer")
        })?),
    };

    let result = backend
        .get_changes::<PresenceStatus>(&account_id, &since_state, max_changes)
        .await
        .map_err(JmapError::from)?;

    Ok((
        json!({
            "accountId": account_id.as_ref(),
            "oldState": since_state.as_ref(),
            "newState": result.new_state.as_ref(),
            "hasMoreChanges": result.has_more_changes,
            "updatedProperties": Value::Null,
            "created":   result.created.iter().map(|id| id.as_ref()).collect::<Vec<_>>(),
            "updated":   result.updated.iter().map(|id| id.as_ref()).collect::<Vec<_>>(),
            "destroyed": result.destroyed.iter().map(|id| id.as_ref()).collect::<Vec<_>>(),
        }),
        vec![],
    ))
}

// ---------------------------------------------------------------------------
// PresenceStatus/set
// ---------------------------------------------------------------------------

/// Handle a `PresenceStatus/set` method call.
///
/// PresenceStatus is a singleton — create and destroy are forbidden. Only
/// `update` is permitted. `id` is immutable; `updatedAt` is always injected
/// server-side and MUST NOT be accepted from the client body.
pub async fn handle_presence_set<B: ChatBackend>(
    backend: &B,
    args: Value,
) -> Result<(Value, Vec<Invocation>), JmapError> {
    let account_id = extract_account_id(&args)?;
    let Value::Object(mut args) = args else {
        return Err(JmapError::invalid_arguments(
            "arguments must be a JSON object",
        ));
    };

    let old_state = backend
        .get_state::<PresenceStatus>(&account_id)
        .await
        .map_err(|e| JmapError::server_fail(e.to_string()))?;

    if let Some(if_in_state) = args.get("ifInState").and_then(|v| v.as_str()) {
        if if_in_state != old_state.as_ref() {
            return Err(JmapError::state_mismatch());
        }
    }

    let created = serde_json::Map::new();
    let mut not_created = serde_json::Map::new();
    let mut updated = serde_json::Map::new();
    let mut not_updated = serde_json::Map::new();
    let destroyed_list: Vec<Value> = Vec::new();
    let mut not_destroyed = serde_json::Map::new();
    let mut mutated = false;

    // -----------------------------------------------------------------------
    // create — forbidden: PresenceStatus is a server-managed singleton
    // -----------------------------------------------------------------------
    if let Some(create_map) = args.get("create").and_then(|v| v.as_object()) {
        for create_id in create_map.keys() {
            not_created.insert(
                create_id.clone(),
                set_error_value(&SetError::new(SetErrorType::Forbidden)),
            );
        }
    }

    // -----------------------------------------------------------------------
    // update
    // -----------------------------------------------------------------------
    if let Some(Value::Object(update_map)) = args.remove("update") {
        for (id_str, patch_val) in update_map {
            let id = Id::from(id_str.as_str());

            // Reject patches that include server-set readonly fields.
            const PRESENCE_READONLY: &[&str] = &["id", "updatedAt"];
            let bad_props: Vec<&str> = PRESENCE_READONLY
                .iter()
                .copied()
                .filter(|&field| patch_val.get(field).is_some())
                .collect();
            if !bad_props.is_empty() {
                not_updated.insert(
                    id_str,
                    json!({ "type": "invalidProperties", "properties": bad_props }),
                );
                continue;
            }

            // Inject server-set updatedAt before forwarding to backend.
            let mut patch = patch_val;
            if let Some(obj) = patch.as_object_mut() {
                obj.insert("updatedAt".to_owned(), json!(now_utc_string()));
            }

            match backend
                .update_object::<PresenceStatus>(&account_id, &id, patch)
                .await
            {
                Ok(Some(obj)) => {
                    mutated = true;
                    updated.insert(id_str, serde_json::to_value(&obj).unwrap_or_else(|e| serde_json::json!({ "type": "serverFail", "description": e.to_string() })));
                }
                Ok(None) => {
                    mutated = true;
                    updated.insert(id_str, Value::Null);
                }
                Err(BackendSetError::SetError(set_err)) => {
                    not_updated.insert(id_str, set_error_value(&set_err));
                }
                Err(BackendSetError::Other(e)) => {
                    not_updated.insert(
                        id_str,
                        json!({ "type": "serverFail", "description": e.to_string() }),
                    );
                }
            }
        }
    }

    // -----------------------------------------------------------------------
    // destroy — forbidden: PresenceStatus is a server-managed singleton
    // -----------------------------------------------------------------------
    if let Some(destroy_arr) = args.get("destroy").and_then(|v| v.as_array()) {
        for id_val in destroy_arr {
            let id_str = match id_val.as_str() {
                Some(s) => s,
                None => continue,
            };
            not_destroyed.insert(
                id_str.to_owned(),
                set_error_value(&SetError::new(SetErrorType::Forbidden)),
            );
        }
    }

    let new_state = if mutated {
        backend
            .get_state::<PresenceStatus>(&account_id)
            .await
            .map_err(|e| JmapError::server_fail(e.to_string()))?
    } else {
        old_state.clone()
    };

    Ok((
        json!({
            "accountId": account_id.as_ref(),
            "oldState": old_state.as_ref(),
            "newState": new_state.as_ref(),
            "created": if created.is_empty() { Value::Null } else { Value::Object(created) },
            "updated": if updated.is_empty() { Value::Null } else { Value::Object(updated) },
            "destroyed": if destroyed_list.is_empty() { Value::Null } else { Value::Array(destroyed_list) },
            "notCreated": if not_created.is_empty() { Value::Null } else { Value::Object(not_created) },
            "notUpdated": if not_updated.is_empty() { Value::Null } else { Value::Object(not_updated) },
            "notDestroyed": if not_destroyed.is_empty() { Value::Null } else { Value::Object(not_destroyed) },
        }),
        vec![],
    ))
}
