//! Point of Interest data model (#148).
//!
//! POIs are discoverable world locations: quest-relevant places, hidden
//! areas, landmarks, vendors, etc. They integrate with the knowledge
//! graph via `FactId("poi.*")` namespace per D-079.
//!
//! Discovery system (#149) uses `KnowledgeEventType::KnowledgeGranted`
//! with `Fact` variant to grant POI facts to observers.

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

use crate::knowledge::types::FactId;
use crate::simulation::movement::TilePosition;

/// Category of point of interest. Determines client-side icon and color.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub enum PoiCategory {
    /// Named location (dock, bar, office, residential block).
    Location,
    /// Vendor or service provider (fixer, medic, data broker).
    Service,
    /// Quest-relevant target (drop point, meeting place, evidence site).
    QuestTarget,
    /// Hidden area (secret passage, concealed cache, restricted zone).
    Hidden,
    /// Navigation landmark visible from a distance.
    Landmark,
}

/// How a POI was placed in the world (content provenance).
///
/// Distinct from visibility rules: discovery_source tracks *why* the POI
/// exists; visibility tracks *how* it can be found.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub enum PoiDiscoverySource {
    /// Part of the map template — always present on this map.
    MapTemplate,
    /// Procedurally generated at world creation.
    Procedural,
    /// Created by a quest or storyline event at runtime.
    QuestGenerated,
    /// Revealed by NPC testimony via knowledge grant.
    NpcRevealed,
}

/// Rules governing when an observer can discover this POI.
///
/// Discovery adds `FactId("poi.{poi_id}")` to the observer's knowledge
/// graph. The discovery system (#149) evaluates these rules each tick
/// for POIs not yet known to the observer.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum PoiVisibility {
    /// Discoverable when within line of sight (standard LOS rules).
    LineOfSight,
    /// Discoverable only within a specific tile range (Manhattan distance).
    Proximity { range: u32 },
    /// Not discoverable by observation. Requires a `KnowledgeGranted`
    /// event from dialogue, evidence, or NPC testimony.
    KnowledgeOnly,
    /// Discoverable by LOS, but only if the observer already knows a
    /// prerequisite fact. Example: a hidden door visible only if the
    /// observer knows `"quest.secret_passage_hint"`.
    RequiresFact { fact_id: String },
}

/// Point of Interest ECS component (#148).
///
/// Attached to world entities that represent discoverable locations.
/// When an observer discovers a POI, `FactId("poi.{poi_id}")` is added
/// to their `KnowledgeGraph` via the discovery system (#149).
///
/// BTreeMap ordering note: POI entities use `StableEntityId` like all
/// other entities. The `poi_id` string is for the fact namespace only.
#[derive(Component, Debug, Clone, Serialize, Deserialize)]
pub struct PointOfInterest {
    /// Unique identifier within the `poi.*` fact namespace.
    /// Format: `lowercase_snake_case`. Example: `"docking_bay_7"`.
    /// Must be unique across all POIs in the world.
    pub poi_id: String,
    /// Display name shown to the player after discovery.
    pub name: String,
    /// World position of the POI (center tile).
    pub position: TilePosition,
    /// Category for client-side rendering (icon, minimap marker).
    pub category: PoiCategory,
    /// Content provenance — how this POI was placed in the world.
    pub discovery_source: PoiDiscoverySource,
    /// Rules for when/how an observer can discover this POI.
    pub visibility: PoiVisibility,
}

impl PointOfInterest {
    /// Generate the `FactId` for this POI in the knowledge graph.
    /// Format: `"poi.{poi_id}"` per D-079 namespace convention.
    pub fn fact_id(&self) -> FactId {
        FactId(format!("poi.{}", self.poi_id))
    }
}

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

    fn make_poi(id: &str, category: PoiCategory, visibility: PoiVisibility) -> PointOfInterest {
        PointOfInterest {
            poi_id: id.to_string(),
            name: format!("Test POI {}", id),
            position: TilePosition::new(10, 20, 0),
            category,
            discovery_source: PoiDiscoverySource::MapTemplate,
            visibility,
        }
    }

    #[test]
    fn fact_id_uses_poi_namespace() {
        let poi = make_poi("docking_bay_7", PoiCategory::Location, PoiVisibility::LineOfSight);
        assert_eq!(poi.fact_id(), FactId("poi.docking_bay_7".to_string()));
    }

    #[test]
    fn fact_id_format_is_deterministic() {
        let poi1 = make_poi("cargo_hold", PoiCategory::Hidden, PoiVisibility::KnowledgeOnly);
        let poi2 = make_poi("cargo_hold", PoiCategory::Hidden, PoiVisibility::KnowledgeOnly);
        assert_eq!(poi1.fact_id(), poi2.fact_id());
    }

    #[test]
    fn different_poi_ids_produce_different_fact_ids() {
        let poi1 = make_poi("bay_alpha", PoiCategory::Location, PoiVisibility::LineOfSight);
        let poi2 = make_poi("bay_beta", PoiCategory::Location, PoiVisibility::LineOfSight);
        assert_ne!(poi1.fact_id(), poi2.fact_id());
    }

    #[test]
    fn proximity_visibility_stores_range() {
        let poi = make_poi(
            "hidden_cache",
            PoiCategory::Hidden,
            PoiVisibility::Proximity { range: 5 },
        );
        match poi.visibility {
            PoiVisibility::Proximity { range } => assert_eq!(range, 5),
            _ => panic!("Expected Proximity visibility"),
        }
    }

    #[test]
    fn requires_fact_visibility_stores_fact_id() {
        let poi = make_poi(
            "secret_door",
            PoiCategory::Hidden,
            PoiVisibility::RequiresFact {
                fact_id: "quest.secret_passage_hint".to_string(),
            },
        );
        match &poi.visibility {
            PoiVisibility::RequiresFact { fact_id } => {
                assert_eq!(fact_id, "quest.secret_passage_hint");
            }
            _ => panic!("Expected RequiresFact visibility"),
        }
    }

    #[test]
    fn poi_categories_are_distinct() {
        assert_ne!(PoiCategory::Location, PoiCategory::Service);
        assert_ne!(PoiCategory::QuestTarget, PoiCategory::Hidden);
        assert_ne!(PoiCategory::Hidden, PoiCategory::Landmark);
    }

    #[test]
    fn poi_discovery_sources_are_distinct() {
        assert_ne!(PoiDiscoverySource::MapTemplate, PoiDiscoverySource::Procedural);
        assert_ne!(
            PoiDiscoverySource::QuestGenerated,
            PoiDiscoverySource::NpcRevealed
        );
    }

    #[test]
    fn poi_serialization_roundtrip() {
        let poi = make_poi("med_bay", PoiCategory::Service, PoiVisibility::LineOfSight);
        let serialized = serde_yaml::to_string(&poi).expect("serialize");
        let deserialized: PointOfInterest =
            serde_yaml::from_str(&serialized).expect("deserialize");
        assert_eq!(deserialized.poi_id, "med_bay");
        assert_eq!(deserialized.category, PoiCategory::Service);
    }
}