import { SETTINGS_KEYS, SYNCABLE_PARAMETERS } from '$lib/constants';
import { ParameterSource, SyncableParameterType } from '$lib/enums';
import type { ParameterInfo, ParameterRecord, ParameterValue } from '$lib/types';
import { normalizeFloatingPoint } from '$lib/utils';

export class ParameterSyncService {
	/**
	 *
	 *
	 * Extraction
	 *
	 *
	 */

	/**
	 * Round floating-point numbers to avoid JavaScript precision issues.
	 * E.g., 0.1 + 0.2 = 0.30000000000000004 → 0.3
	 *
	 * @param value - Parameter value to normalize
	 * @returns Precision-normalized value
	 */
	private static roundFloatingPoint(value: ParameterValue): ParameterValue {
		return normalizeFloatingPoint(value) as ParameterValue;
	}

	/**
	 * Extract server default parameters that can be synced from `/props` response.
	 * Handles both generation settings parameters and UI-specific settings.
	 * Converts samplers array to semicolon-delimited string for UI display.
	 *
	 * @param serverParams - Raw generation settings from server `/props` endpoint
	 * @returns Record of extracted parameter key-value pairs with normalized precision
	 */
	static extractServerDefaults(
		serverParams: ApiLlamaCppServerProps['default_generation_settings']['params'] | null
	): ParameterRecord {
		const extracted: ParameterRecord = {};

		if (serverParams) {
			for (const param of SYNCABLE_PARAMETERS) {
				if (param.canSync && param.serverKey in serverParams) {
					const value = (serverParams as unknown as Record<string, ParameterValue>)[
						param.serverKey
					];

					if (value !== undefined) {
						// Apply precision rounding to avoid JavaScript floating-point issues
						extracted[param.key] = this.roundFloatingPoint(value);
					}
				}
			}

			// Handle samplers array conversion to string
			if (serverParams.samplers && Array.isArray(serverParams.samplers)) {
				extracted[SETTINGS_KEYS.SAMPLERS] = serverParams.samplers.join(';');
			}
		}

		return extracted;
	}

	/**
	 *
	 *
	 * Merging
	 *
	 *
	 */

	/**
	 * Merge server defaults with current user settings.
	 * User overrides always take priority — only parameters not in `userOverrides`
	 * set will be updated from server defaults.
	 *
	 * @param currentSettings - Current parameter values in the settings store
	 * @param serverDefaults - Default values extracted from server props
	 * @param userOverrides - Set of parameter keys explicitly overridden by the user
	 * @returns Merged parameter record with user overrides preserved
	 */
	static mergeWithServerDefaults(
		currentSettings: ParameterRecord,
		serverDefaults: ParameterRecord,
		userOverrides: Set<string> = new Set()
	): ParameterRecord {
		const merged = { ...currentSettings };

		for (const [key, serverValue] of Object.entries(serverDefaults)) {
			// Only update if user hasn't explicitly overridden this parameter
			if (!userOverrides.has(key)) {
				merged[key] = this.roundFloatingPoint(serverValue);
			}
		}

		return merged;
	}

	/**
	 *
	 *
	 * Info
	 *
	 *
	 */

	/**
	 * Get parameter information including source and values.
	 * Used by SettingsChatParameterSourceIndicator to display the correct badge
	 * (Custom vs Default) for each parameter in the settings UI.
	 *
	 * @param key - The parameter key to get info for
	 * @param currentValue - The current value of the parameter
	 * @param propsDefaults - Server default values from `/props`
	 * @param userOverrides - Set of parameter keys explicitly overridden by the user
	 * @returns Parameter info with source, server default, and user override values
	 */
	static getParameterInfo(
		key: string,
		currentValue: ParameterValue,
		propsDefaults: ParameterRecord,
		userOverrides: Set<string>
	): ParameterInfo {
		const hasPropsDefault = propsDefaults[key] !== undefined;
		const isUserOverride = userOverrides.has(key);
		// Simple logic: either using default (from props) or custom (user override)
		const source = isUserOverride ? ParameterSource.CUSTOM : ParameterSource.DEFAULT;

		return {
			serverDefault: hasPropsDefault ? propsDefaults[key] : undefined, // Keep same field name for compatibility
			source,
			userOverride: isUserOverride ? currentValue : undefined,
			value: currentValue
		};
	}

	/**
	 * Check if a parameter can be synced from server.
	 *
	 * @param key - The parameter key to check
	 * @returns True if the parameter is in the syncable parameters list
	 */
	static canSyncParameter(key: string): boolean {
		return SYNCABLE_PARAMETERS.some((param) => param.key === key && param.canSync);
	}

	/**
	 * Get all syncable parameter keys.
	 *
	 * @returns Array of parameter keys that can be synced from server
	 */
	static getSyncableParameterKeys(): string[] {
		return SYNCABLE_PARAMETERS.filter((param) => param.canSync).map((param) => param.key);
	}

	/**
	 * Validate a server parameter value against its expected type.
	 *
	 * @param key - The parameter key to validate
	 * @param value - The value to validate
	 * @returns True if value matches the expected type for this parameter
	 */
	static validateServerParameter(key: string, value: ParameterValue): boolean {
		const param = SYNCABLE_PARAMETERS.find((p) => p.key === key);

		if (!param) return false;

		switch (param.type) {
			case SyncableParameterType.NUMBER:
				return typeof value === 'number' && !isNaN(value);
			case SyncableParameterType.STRING:
				return typeof value === 'string';
			case SyncableParameterType.BOOLEAN:
				return typeof value === 'boolean';
			default:
				return false;
		}
	}

	/**
	 *
	 *
	 * Diff
	 *
	 *
	 */

	/**
	 * Create a diff between current settings and server defaults.
	 * Shows which parameters differ from server values, useful for debugging
	 * and for the "Reset to defaults" functionality.
	 *
	 * @param currentSettings - Current parameter values in the settings store
	 * @param serverDefaults - Default values extracted from server props
	 * @returns Record of parameter diffs with current value, server value, and whether they differ
	 */
	static createParameterDiff(
		currentSettings: ParameterRecord,
		serverDefaults: ParameterRecord
	): Record<string, { current: ParameterValue; server: ParameterValue; differs: boolean }> {
		const diff: Record<
			string,
			{ current: ParameterValue; server: ParameterValue; differs: boolean }
		> = {};

		for (const key of this.getSyncableParameterKeys()) {
			const currentValue = currentSettings[key];
			const serverValue = serverDefaults[key];

			if (serverValue !== undefined) {
				diff[key] = {
					current: currentValue,
					differs: currentValue !== serverValue,
					server: serverValue
				};
			}
		}

		return diff;
	}
}