"use client";

import React, { useState, useCallback, useEffect, useRef } from "react";
import {
    AdminPanelConfig,
    AdminPanelState,
    UseAdminPanelOptions,
    UseAdminPanelReturn,
    FieldConfig,
    ValidationRule
} from "@/types/admin-panel";

// Helper function to get nested value
function getNestedValue(obj: any, path: string): any {
    return path.split('.').reduce((current, key) => current?.[key], obj);
}

// Helper function to set nested value
function setNestedValue(obj: any, path: string, value: any): any {
    const keys = path.split('.');
    const result = { ...obj };
    let current = result;

    for (let i = 0; i < keys.length - 1; i++) {
        const key = keys[i];
        current[key] = current[key] ? { ...current[key] } : {};
        current = current[key];
    }

    current[keys[keys.length - 1]] = value;
    return result;
}

// Helper function to validate a field
function validateField(field: FieldConfig, value: any): string | null {
    if (!field.validation) return null;

    const { validation } = field;

    // Required validation
    if (validation.required && (value === undefined || value === null || value === '')) {
        return `${field.label}是必填项`;
    }

    // Skip other validations if value is empty and not required
    if (value === undefined || value === null || value === '') {
        return null;
    }

    // Min/Max validation for numbers
    if (typeof value === 'number') {
        if (validation.min !== undefined && value < validation.min) {
            return `${field.label}不能小于${validation.min}`;
        }
        if (validation.max !== undefined && value > validation.max) {
            return `${field.label}不能大于${validation.max}`;
        }
    }

    // Length validation for strings
    if (typeof value === 'string') {
        if (validation.minLength !== undefined && value.length < validation.minLength) {
            return `${field.label}长度不能少于${validation.minLength}个字符`;
        }
        if (validation.maxLength !== undefined && value.length > validation.maxLength) {
            return `${field.label}长度不能超过${validation.maxLength}个字符`;
        }
    }

    // Pattern validation
    if (validation.pattern && typeof value === 'string' && !validation.pattern.test(value)) {
        return `${field.label}格式不正确`;
    }

    // Custom validation
    if (validation.custom) {
        return validation.custom(value);
    }

    return null;
}

// Get all fields from config
function getAllFields(config: AdminPanelConfig): FieldConfig[] {
    return config.tabs.flatMap(tab =>
        tab.sections.flatMap(section => section.fields)
    );
}

export function useAdminPanel(options: UseAdminPanelOptions): UseAdminPanelReturn {
    const { config, initialValues = {}, onSubmit } = options;

    // State
    const [state, setState] = useState<AdminPanelState>({
        values: initialValues,
        errors: {},
        dirty: {},
        loading: false,
        saving: false,
    });

    // Auto-save timer
    const autoSaveTimer = useRef<NodeJS.Timeout | null>(null);
    const lastSavedValues = useRef<Record<string, any>>(initialValues);

    // Calculate initial values with memoization to prevent unnecessary recalculations
    const computedInitialValues = React.useMemo(() => {
        const fields = getAllFields(config);
        const values: Record<string, any> = { ...initialValues };

        fields.forEach(field => {
            if (getNestedValue(values, field.id) === undefined) {
                setNestedValue(values, field.id, field.value);
            }
        });

        return values;
    }, [config, initialValues]);

    // Initialize values only when computed initial values change
    useEffect(() => {
        setState(prev => {
            // Only update if values are actually different to prevent loops
            const currentJson = JSON.stringify(prev.values);
            const newJson = JSON.stringify(computedInitialValues);
            if (currentJson !== newJson) {
                lastSavedValues.current = computedInitialValues;
                return { ...prev, values: computedInitialValues };
            }
            return prev;
        });
    }, [computedInitialValues]); // Depend directly on memoized values

    // Auto-save functionality
    useEffect(() => {
        if (!config.autoSave || !onSubmit) return;

        const delay = config.autoSaveDelay || 2000;

        if (autoSaveTimer.current) {
            clearTimeout(autoSaveTimer.current);
        }

        // Check if values have changed
        const hasChanges = JSON.stringify(state.values) !== JSON.stringify(lastSavedValues.current);

        if (hasChanges && Object.keys(state.dirty).length > 0) {
            autoSaveTimer.current = setTimeout(async () => {
                try {
                    await onSubmit(state.values);
                    lastSavedValues.current = state.values;
                    setState(prev => ({ ...prev, dirty: {} }));
                } catch (error) {
                    console.error('Auto-save failed:', error);
                }
            }, delay);
        }

        return () => {
            if (autoSaveTimer.current) {
                clearTimeout(autoSaveTimer.current);
            }
        };
    }, [state.values, state.dirty, config.autoSave, config.autoSaveDelay, onSubmit]);

    // Actions
    const setValue = useCallback((path: string, value: any) => {
        setState(prev => {
            const newValues = setNestedValue(prev.values, path, value);
            const newDirty = { ...prev.dirty, [path]: true };

            // Clear error for this field
            const newErrors = { ...prev.errors };
            delete newErrors[path];

            // Validate on change if enabled
            let validationErrors = newErrors;
            if (config.validateOnChange) {
                const fields = getAllFields(config);
                const field = fields.find(f => f.id === path);
                if (field) {
                    const error = validateField(field, value);
                    if (error) {
                        validationErrors = { ...validationErrors, [path]: error };
                    }
                }
            }

            // Call onChange callback
            if (config.onValueChange) {
                config.onValueChange(path, value, newValues);
            }

            return {
                ...prev,
                values: newValues,
                dirty: newDirty,
                errors: validationErrors,
            };
        });
    }, [config]);

    const setValues = useCallback((values: Record<string, any>) => {
        setState(prev => ({
            ...prev,
            values: { ...prev.values, ...values },
            dirty: Object.keys(values).reduce((acc, key) => ({ ...acc, [key]: true }), prev.dirty),
        }));
    }, []);

    const resetValue = useCallback((path: string) => {
        const fields = getAllFields(config);
        const field = fields.find(f => f.id === path);
        if (field) {
            setValue(path, field.value);
            setState(prev => {
                const newDirty = { ...prev.dirty };
                delete newDirty[path];
                const newErrors = { ...prev.errors };
                delete newErrors[path];
                return { ...prev, dirty: newDirty, errors: newErrors };
            });
        }
    }, [config, setValue]);

    const resetAll = useCallback(() => {
        setState(prev => ({
            ...prev,
            values: computedInitialValues,
            dirty: {},
            errors: {},
        }));
        if (config.onReset) {
            config.onReset();
        }
    }, [computedInitialValues, config]);

    const validate = useCallback((): boolean => {
        const fields = getAllFields(config);
        const errors: Record<string, string> = {};

        fields.forEach(field => {
            // Skip validation for disabled or readOnly fields
            if (field.disabled || field.readOnly) return;

            // Check conditional rendering
            if (field.showWhen && !field.showWhen(state.values)) return;

            const value = getNestedValue(state.values, field.id);
            const error = validateField(field, value);
            if (error) {
                errors[field.id] = error;
            }
        });

        // Custom validation
        if (config.onValidate) {
            const customErrors = config.onValidate(state.values);
            Object.assign(errors, customErrors);
        }

        setState(prev => ({ ...prev, errors }));
        return Object.keys(errors).length === 0;
    }, [config, state.values]);

    const save = useCallback(async () => {
        if (!onSubmit) return;

        // Validate if required
        if (config.validateOnSubmit !== false) {
            const isValid = validate();
            if (!isValid) return;
        }

        setState(prev => ({ ...prev, saving: true }));

        try {
            await onSubmit(state.values);
            lastSavedValues.current = state.values;
            setState(prev => ({
                ...prev,
                saving: false,
                dirty: {},
                errors: {}
            }));

            if (config.onSave) {
                await config.onSave(state.values);
            }
        } catch (error) {
            setState(prev => ({ ...prev, saving: false }));
            throw error;
        }
    }, [config, state.values, onSubmit, validate]);

    const clearErrors = useCallback(() => {
        setState(prev => ({ ...prev, errors: {} }));
    }, []);

    // Helpers
    const getValue = useCallback((path: string) => {
        return getNestedValue(state.values, path);
    }, [state.values]);

    const getError = useCallback((path: string) => {
        return state.errors[path];
    }, [state.errors]);

    const isDirty = useCallback((path?: string) => {
        if (path) {
            return Boolean(state.dirty[path]);
        }
        return Object.keys(state.dirty).length > 0;
    }, [state.dirty]);

    const isValid = useCallback((path?: string) => {
        if (path) {
            return !state.errors[path];
        }
        return Object.keys(state.errors).length === 0;
    }, [state.errors]);

    return {
        state,
        actions: {
            setValue,
            setValues,
            resetValue,
            resetAll,
            save,
            validate,
            clearErrors,
        },
        helpers: {
            getValue,
            getError,
            isDirty,
            isValid,
        },
    };
}