use crate::cartridge::{Capability, Cartridge, CartridgeDTO, CartridgeError, CartridgeManifest};
use crate::syscalls::{CapFlags, caps};
use std::collections::HashSet;
use std::fs;
use std::path::Path;

pub struct CartridgeLoader;

impl CartridgeLoader {
    pub fn load(path: impl AsRef<Path>) -> Result<Cartridge, CartridgeError> {
        let path = path.as_ref();
        if !path.exists() {
            return Err(CartridgeError::NotFound);
        }

        if path.is_dir() {
            DirectoryCartridgeLoader::load(path)
        } else if path.extension().is_some_and(|ext| ext == "pmc") {
            PackedCartridgeLoader::load(path)
        } else {
            Err(CartridgeError::InvalidFormat)
        }
    }
}

pub struct DirectoryCartridgeLoader;

impl DirectoryCartridgeLoader {
    pub fn load(path: &Path) -> Result<Cartridge, CartridgeError> {
        let manifest_path = path.join("manifest.json");
        if !manifest_path.exists() {
            return Err(CartridgeError::InvalidManifest);
        }

        let manifest_content =
            fs::read_to_string(manifest_path).map_err(|_| CartridgeError::IoError)?;
        let manifest: CartridgeManifest =
            serde_json::from_str(&manifest_content).map_err(|_| CartridgeError::InvalidManifest)?;

        // Additional validation as per requirements
        if manifest.magic != "PMTU" {
            return Err(CartridgeError::InvalidManifest);
        }
        if manifest.cartridge_version != 1 {
            return Err(CartridgeError::UnsupportedVersion);
        }

        let capabilities = normalize_capabilities(&manifest.capabilities)?;

        let program_path = path.join("program.pbx");
        if !program_path.exists() {
            return Err(CartridgeError::MissingProgram);
        }

        let program = fs::read(program_path).map_err(|_| CartridgeError::IoError)?;

        let assets_pa_path = path.join("assets.pa");
        let assets = if assets_pa_path.exists() {
            fs::read(assets_pa_path).map_err(|_| CartridgeError::IoError)?
        } else {
            Vec::new()
        };

        let dto = CartridgeDTO {
            app_id: manifest.app_id,
            title: manifest.title,
            app_version: manifest.app_version,
            app_mode: manifest.app_mode,
            entrypoint: manifest.entrypoint,
            capabilities,
            program,
            assets,
            asset_table: manifest.asset_table,
            preload: manifest.preload,
        };

        Ok(Cartridge::from(dto))
    }
}

pub struct PackedCartridgeLoader;

impl PackedCartridgeLoader {
    pub fn load(_path: &Path) -> Result<Cartridge, CartridgeError> {
        Err(CartridgeError::InvalidFormat)
    }
}

fn normalize_capabilities(capabilities: &[Capability]) -> Result<CapFlags, CartridgeError> {
    let mut seen = HashSet::new();
    let mut normalized = caps::NONE;

    for capability in capabilities {
        if !seen.insert(*capability) {
            return Err(CartridgeError::InvalidManifest);
        }

        normalized |= match capability {
            Capability::None => caps::NONE,
            Capability::System => caps::SYSTEM,
            Capability::Gfx => caps::GFX,
            Capability::Audio => caps::AUDIO,
            Capability::Fs => caps::FS,
            Capability::Log => caps::LOG,
            Capability::Asset => caps::ASSET,
            Capability::Bank => caps::BANK,
            Capability::All => caps::ALL,
        };
    }

    Ok(normalized)
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde_json::json;
    use std::path::{Path, PathBuf};
    use std::sync::atomic::{AtomicU64, Ordering};
    use std::time::{SystemTime, UNIX_EPOCH};

    static TEST_DIR_COUNTER: AtomicU64 = AtomicU64::new(0);

    struct TestCartridgeDir {
        path: PathBuf,
    }

    impl TestCartridgeDir {
        fn new(manifest: serde_json::Value) -> Self {
            let unique = TEST_DIR_COUNTER.fetch_add(1, Ordering::Relaxed);
            let timestamp = SystemTime::now()
                .duration_since(UNIX_EPOCH)
                .expect("system time must be after unix epoch")
                .as_nanos();
            let path = std::env::temp_dir()
                .join(format!("prometeu-hal-cartridge-loader-{}-{}", timestamp, unique));

            fs::create_dir_all(&path).expect("must create temporary cartridge directory");
            fs::write(
                path.join("manifest.json"),
                serde_json::to_vec_pretty(&manifest).expect("manifest must serialize"),
            )
            .expect("must write manifest.json");
            fs::write(path.join("program.pbx"), [0x01_u8, 0x02, 0x03]).expect("must write program");

            Self { path }
        }

        fn path(&self) -> &Path {
            &self.path
        }
    }

    impl Drop for TestCartridgeDir {
        fn drop(&mut self) {
            let _ = fs::remove_dir_all(&self.path);
        }
    }

    fn manifest_with_capabilities(capabilities: Option<Vec<&str>>) -> serde_json::Value {
        let mut manifest = json!({
            "magic": "PMTU",
            "cartridge_version": 1,
            "app_id": 1001,
            "title": "Example",
            "app_version": "1.0.0",
            "app_mode": "Game",
            "entrypoint": "main"
        });

        if let Some(capabilities) = capabilities {
            manifest["capabilities"] = json!(capabilities);
        }

        manifest
    }

    #[test]
    fn load_without_capabilities_defaults_to_none() {
        let dir = TestCartridgeDir::new(manifest_with_capabilities(None));

        let cartridge = DirectoryCartridgeLoader::load(dir.path()).expect("cartridge must load");

        assert_eq!(cartridge.capabilities, caps::NONE);
    }

    #[test]
    fn load_with_single_capability_normalizes_to_flag() {
        let dir = TestCartridgeDir::new(manifest_with_capabilities(Some(vec!["gfx"])));

        let cartridge = DirectoryCartridgeLoader::load(dir.path()).expect("cartridge must load");

        assert_eq!(cartridge.capabilities, caps::GFX);
    }

    #[test]
    fn load_with_multiple_capabilities_combines_flags() {
        let dir = TestCartridgeDir::new(manifest_with_capabilities(Some(vec!["gfx", "audio"])));

        let cartridge = DirectoryCartridgeLoader::load(dir.path()).expect("cartridge must load");

        assert_eq!(cartridge.capabilities, caps::GFX | caps::AUDIO);
    }

    #[test]
    fn load_with_all_capability_normalizes_to_all_flags() {
        let dir = TestCartridgeDir::new(manifest_with_capabilities(Some(vec!["all"])));

        let cartridge = DirectoryCartridgeLoader::load(dir.path()).expect("cartridge must load");

        assert_eq!(cartridge.capabilities, caps::ALL);
    }

    #[test]
    fn load_with_none_capability_keeps_zero_flags() {
        let dir = TestCartridgeDir::new(manifest_with_capabilities(Some(vec!["none"])));

        let cartridge = DirectoryCartridgeLoader::load(dir.path()).expect("cartridge must load");

        assert_eq!(cartridge.capabilities, caps::NONE);
    }

    #[test]
    fn load_with_duplicate_capabilities_fails() {
        let dir = TestCartridgeDir::new(manifest_with_capabilities(Some(vec!["gfx", "gfx"])));

        let error = DirectoryCartridgeLoader::load(dir.path()).unwrap_err();

        assert!(matches!(error, CartridgeError::InvalidManifest));
    }

    #[test]
    fn load_with_unknown_capability_fails() {
        let dir = TestCartridgeDir::new(manifest_with_capabilities(Some(vec!["network"])));

        let error = DirectoryCartridgeLoader::load(dir.path()).unwrap_err();

        assert!(matches!(error, CartridgeError::InvalidManifest));
    }

    #[test]
    fn load_with_legacy_input_capability_fails() {
        let dir = TestCartridgeDir::new(manifest_with_capabilities(Some(vec!["input"])));

        let error = DirectoryCartridgeLoader::load(dir.path()).unwrap_err();

        assert!(matches!(error, CartridgeError::InvalidManifest));
    }
}