//! Scene file schema versioning for `assets/levels/*.scn.ron`.
//!
//! Bevy dynamic scenes are stored as RON tuples. On save the editor stamps
//! `schema_version` as the first root field; loaders strip it before deserializing.

mod migrate;

use std::path::Path;

use serde::{Deserialize, Serialize};

pub use migrate::{migrate_v1_to_v2, DEFAULT_SUN_ILLUMINANCE_LUX};

pub const CURRENT_SCENE_SCHEMA_VERSION: u32 = 2;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SceneSchemaHeader {
    pub schema_version: u32,
}

impl Default for SceneSchemaHeader {
    fn default() -> Self {
        Self {
            schema_version: CURRENT_SCENE_SCHEMA_VERSION,
        }
    }
}

fn read_schema_version(text: &str) -> u32 {
    let trimmed = text.trim();
    if !trimmed.starts_with("(schema_version:") {
        return 1;
    }
    let inner = trimmed
        .strip_prefix('(')
        .and_then(|s| s.strip_prefix("schema_version:"))
        .unwrap_or("");
    let version_str = inner.trim().split(',').next().unwrap_or("1").trim();
    version_str.parse().unwrap_or(1)
}

/// Inserts `schema_version` as the first field of a Bevy dynamic-scene RON root tuple.
pub fn stamp_schema_version(text: &str) -> Result<String, String> {
    let trimmed = text.trim();
    if trimmed.starts_with("(schema_version:") {
        let version = read_schema_version(trimmed);
        if version == CURRENT_SCENE_SCHEMA_VERSION {
            return Ok(trimmed.to_string());
        }
        let body = strip_schema_version(trimmed)?;
        return stamp_schema_version(&body);
    }
    if !trimmed.starts_with('(') || !trimmed.ends_with(')') {
        return Err("expected scene RON root tuple".into());
    }
    Ok(format!(
        "(schema_version: {},{}",
        CURRENT_SCENE_SCHEMA_VERSION,
        &trimmed[1..]
    ))
}

/// Applies versioned migrations and stamps the current schema header.
pub fn migrate_scene_text(text: &str) -> Result<String, String> {
    let trimmed = text.trim();
    let version = read_schema_version(trimmed);
    let body = if trimmed.starts_with("(schema_version:") {
        strip_schema_version(trimmed)?
    } else {
        trimmed.to_string()
    };

    let migrated_body = match version {
        0 | 1 => migrate_v1_to_v2(&body),
        2 => body,
        _ => body,
    };

    stamp_schema_version(&migrated_body)
}

/// Removes the schema header so Bevy can deserialize the dynamic scene body.
pub fn strip_schema_version(text: &str) -> Result<String, String> {
    let trimmed = text.trim();
    if !trimmed.starts_with("(schema_version:") {
        return Ok(trimmed.to_string());
    }
    let inner = trimmed
        .strip_prefix('(')
        .ok_or_else(|| "invalid schema wrapper".to_string())?;
    let after_key = inner
        .strip_prefix("schema_version:")
        .ok_or_else(|| "invalid schema_version prefix".to_string())?;
    let comma = after_key
        .find(',')
        .ok_or_else(|| "schema_version tuple missing body".to_string())?;
    Ok(format!("({}", after_key[comma + 1..].trim_start()))
}

/// Hydrated/runtime component type names that must not appear in saved `.scn.ron` files.
pub const FORBIDDEN_SAVED_COMPONENT_MARKERS: &[&str] = &[
    "bevy_pbr::PointLight",
    "bevy_pbr::SpotLight",
    "bevy_pbr::DirectionalLight",
    "bevy_mesh::Mesh3d",
    "bevy_mesh::MeshMaterial3d",
    "avian3d::RigidBody",
    "avian3d::Collider",
    "bevy_scene::SceneRoot",
    "bevy_render::visibility::ComputedVisibility",
];

/// Ensures serialized scene text does not contain hydrated ECS component entries.
pub fn validate_scene_authoring_only(text: &str) -> Result<(), String> {
    for marker in FORBIDDEN_SAVED_COMPONENT_MARKERS {
        if text.contains(marker) {
            return Err(format!(
                "scene file contains hydrated component marker `{marker}` (save allowlist violation)"
            ));
        }
    }
    Ok(())
}

pub fn validate_level_text(text: &str) -> Result<(), String> {
    if text.trim().is_empty() {
        return Err("empty scene file".into());
    }
    let migrated = migrate_scene_text(text)?;
    strip_schema_version(&migrated)?;
    validate_scene_authoring_only(&migrated)?;
    Ok(())
}

pub fn validate_level_file(path: &Path) -> Result<(), String> {
    let text = std::fs::read_to_string(path).map_err(|e| e.to_string())?;
    validate_level_text(&text)
}

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

    #[test]
    fn stamp_and_strip_round_trip() {
        let body = "(resources: {}, entities: {})";
        let stamped = stamp_schema_version(body).unwrap();
        assert!(stamped.starts_with("(schema_version: 2,"));
        let stripped = strip_schema_version(&stamped).unwrap();
        assert_eq!(stripped, body);
    }

    #[test]
    fn legacy_scene_migrates_to_v2() {
        let legacy = "(resources: {}, entities: {4294967133: ()})";
        let migrated = migrate_scene_text(legacy).unwrap();
        assert!(migrated.contains("schema_version: 2"));
    }

    #[test]
    #[ignore = "run manually to rewrite assets/levels/editor_scene.scn.ron"]
    fn migrate_editor_scene_on_disk() {
        let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
            .join("../../assets/levels/editor_scene.scn.ron");
        let text = std::fs::read_to_string(&path).expect("read editor scene");
        let migrated = migrate_scene_text(&text).expect("migrate");
        std::fs::write(&path, migrated).expect("write migrated scene");
    }

    #[test]
    fn repo_editor_scene_has_no_hydrated_components() {
        let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
            .join("../../assets/levels/editor_scene.scn.ron");
        let text = std::fs::read_to_string(&path).expect("read editor scene");
        validate_scene_authoring_only(&text).expect("editor scene must be authoring-only");
    }

    #[test]
    fn v1_scene_gains_actor_kind_on_migrate() {
        let v1 = "(schema_version: 1,(resources: {}, entities: {
    1: (
      components: {
        \"shared::components::LevelObject\": (),
        \"shared::components::Primitive\": (
          shape: Box,
          size: (1.0, 1.0, 1.0),
        ),
      },
    ),
  }))";
        let migrated = migrate_scene_text(&v1).unwrap();
        assert!(migrated.contains("ActorKind"));
        assert!(migrated.contains("StaticMesh"));
    }
}