use graphite_editor::messages::frontend::utility_types::PersistedState;
use graphite_editor::messages::prelude::DocumentId;
use std::path::PathBuf;

const APP_DIRECTORY_NAME: &str = if cfg!(target_os = "linux") { "graphite" } else { "Graphite" };
const STATE_FILE_NAME: &str = "state.json";
const PREFERENCES_FILE_NAME: &str = "preferences.json";
const DOCUMENTS_DIRECTORY_NAME: &str = "documents";
const DOCUMENT_FILE_EXTENSION: &str = "graphite";

fn root_dir() -> Option<PathBuf> {
	let base = dirs::config_local_dir().or_else(dirs::data_local_dir)?;
	let path = base.join(APP_DIRECTORY_NAME);
	if let Err(e) = std::fs::create_dir_all(&path) {
		tracing::warn!("failed to create graphite config directory at {path:?}: {e}");
		return None;
	}
	Some(path)
}

fn documents_dir() -> Option<PathBuf> {
	let path = root_dir()?.join(DOCUMENTS_DIRECTORY_NAME);
	if let Err(e) = std::fs::create_dir_all(&path) {
		tracing::warn!("failed to create documents directory at {path:?}: {e}");
		return None;
	}
	Some(path)
}

fn state_path() -> Option<PathBuf> {
	Some(root_dir()?.join(STATE_FILE_NAME))
}

fn preferences_path() -> Option<PathBuf> {
	Some(root_dir()?.join(PREFERENCES_FILE_NAME))
}

fn document_path(id: DocumentId) -> Option<PathBuf> {
	Some(documents_dir()?.join(format!("{:x}.{}", id.0, DOCUMENT_FILE_EXTENSION)))
}

pub fn read_state() -> Option<PersistedState> {
	let path = state_path()?;
	let raw = match std::fs::read_to_string(&path) {
		Ok(raw) => raw,
		Err(e) if e.kind() == std::io::ErrorKind::NotFound => return None,
		Err(e) => {
			tracing::warn!("failed to read persisted state from {path:?}: {e}");
			return None;
		}
	};
	match serde_json::from_str::<PersistedState>(&raw) {
		Ok(state) => Some(state),
		Err(e) => {
			tracing::warn!("failed to parse persisted state at {path:?}: {e}");
			None
		}
	}
}

pub fn write_state(state: &PersistedState) {
	let Some(path) = state_path() else { return };
	let serialized = match serde_json::to_string_pretty(state) {
		Ok(s) => s,
		Err(e) => {
			tracing::warn!("failed to serialize persisted state: {e}");
			return;
		}
	};
	if let Err(e) = std::fs::write(&path, serialized) {
		tracing::warn!("failed to write persisted state to {path:?}: {e}");
		return;
	}
	garbage_collect_documents(state);
}

pub fn read_document(document_id: DocumentId) -> Option<String> {
	let path = document_path(document_id)?;
	match std::fs::read_to_string(&path) {
		Ok(content) => Some(content),
		Err(e) if e.kind() == std::io::ErrorKind::NotFound => None,
		Err(e) => {
			tracing::warn!("failed to read document {document_id:?} from {path:?}: {e}");
			None
		}
	}
}

pub fn write_document(document_id: DocumentId, content: &str) {
	let Some(path) = document_path(document_id) else { return };
	if let Err(e) = std::fs::write(&path, content) {
		tracing::warn!("failed to write document {document_id:?} to {path:?}: {e}");
	}
}

pub fn delete_document(document_id: DocumentId) {
	let Some(path) = document_path(document_id) else { return };
	match std::fs::remove_file(&path) {
		Ok(()) => {}
		Err(e) if e.kind() == std::io::ErrorKind::NotFound => {}
		Err(e) => tracing::warn!("failed to delete document {document_id:?} at {path:?}: {e}"),
	}
}

pub fn read_preferences() -> Option<String> {
	let path = preferences_path()?;
	match std::fs::read_to_string(&path) {
		Ok(raw) => Some(raw),
		Err(e) if e.kind() == std::io::ErrorKind::NotFound => None,
		Err(e) => {
			tracing::warn!("failed to read preferences from {path:?}: {e}");
			None
		}
	}
}

pub fn write_preferences(json: &str) {
	let Some(path) = preferences_path() else { return };
	if let Err(e) = std::fs::write(&path, json) {
		tracing::warn!("failed to write preferences to {path:?}: {e}");
	}
}

fn garbage_collect_documents(state: &PersistedState) {
	let Some(dir) = documents_dir() else { return };
	let valid: std::collections::HashSet<PathBuf> = state.documents.iter().filter_map(|doc| document_path(doc.id)).collect();
	let entries = match std::fs::read_dir(&dir) {
		Ok(entries) => entries,
		Err(e) if e.kind() == std::io::ErrorKind::NotFound => return,
		Err(e) => {
			tracing::warn!("failed to scan documents directory at {dir:?}: {e}");
			return;
		}
	};
	for entry in entries.flatten() {
		let path = entry.path();
		if path.is_file() && !valid.contains(&path) {
			if let Err(e) = std::fs::remove_file(&path) {
				tracing::warn!("failed to remove orphaned document at {path:?}: {e}");
			}
		}
	}
}