using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MW.WorkFlow
{
    /// <summary>
    /// 定义工作流的结构，包含所有活动及其跳转规则。
    /// </summary>
    public class WorkflowDefinition
    {
        private readonly Dictionary<string, WorkflowStep> _steps;
        public string InitialStepId { get; private set; }

        public WorkflowDefinition(string initialStepId)
        {
            InitialStepId = initialStepId ?? throw new ArgumentNullException(nameof(initialStepId));
            _steps = new Dictionary<string, WorkflowStep>();
        }

        /// <summary>
        /// 添加一个工作流步骤到定义中。
        /// </summary>
        /// <param name="step">要添加的步骤。</param>
        public void AddStep(WorkflowStep step)
        {
            if (step == null) throw new ArgumentNullException(nameof(step));
            if (_steps.ContainsKey(step.Id))
            {
                throw new ArgumentException($"工作流步骤ID '{step.Id}' 已存在。");
            }
            _steps.Add(step.Id, step);
        }

        /// <summary>
        /// 根据ID获取工作流步骤。
        /// </summary>
        /// <param name="stepId">步骤的唯一ID。</param>
        /// <returns>对应的 WorkflowStep。</returns>
        public WorkflowStep GetStep(string stepId)
        {
            if (_steps.TryGetValue(stepId, out var step))
            {
                return step;
            }
            throw new ArgumentException($"未找到ID为 '{stepId}' 的工作流步骤。");
        }

        public bool ContainsStep(string stepId)
        {
            return !string.IsNullOrWhiteSpace(stepId) && _steps.ContainsKey(stepId);
        }

        /// <summary>
        /// 获取所有步骤的ID列表。
        /// </summary>
        public IEnumerable<string> GetAllStepIds() => _steps.Keys;
    }

    /// <summary>
    /// 表示工作流中的一个步骤，包含一个活动和可能的条件跳转。
    /// </summary>
    public class WorkflowStep
    {
        public string Id { get; } // 步骤的唯一标识符
        public IActivity Activity { get; } // 该步骤要执行的活动
        public string FlowName { get; private set; } // 所属流程名称，用于界面显示和断点定位
        public string NextStepId { get; private set; } // 默认的下一个步骤ID
        public List<JumpCondition> JumpConditions { get; } // 条件跳转列表

        public WorkflowStep(string id, IActivity activity)
        {
            Id = id ?? throw new ArgumentNullException(nameof(id));
            Activity = activity ?? throw new ArgumentNullException(nameof(activity));
            JumpConditions = new List<JumpCondition>();
        }

        /// <summary>
        /// 设置默认的下一个步骤ID。
        /// </summary>
        public WorkflowStep WithNextStep(string nextStepId)
        {
            NextStepId = nextStepId;
            return this;
        }

        public WorkflowStep WithFlowName(string flowName)
        {
            FlowName = flowName;
            return this;
        }

        /// <summary>
        /// 添加一个条件跳转。
        /// </summary>
        /// <param name="condition">跳转条件。</param>
        /// <param name="targetStepId">满足条件时要跳转到的目标步骤ID。</param>
        public WorkflowStep AddJumpCondition(Func<WorkflowContext, ActivityResult, bool> condition, string targetStepId)
        {
            JumpConditions.Add(new JumpCondition(condition, targetStepId));
            return this;
        }

        public WorkflowStep AddDynamicJumpCondition(Func<WorkflowContext, ActivityResult, bool> condition, Func<WorkflowContext, ActivityResult, string> targetStepResolver)
        {
            JumpConditions.Add(new JumpCondition(condition, targetStepResolver));
            return this;
        }

        public WorkflowStep AddJumpOnContextValue<T>(string contextKey, T expectedValue, string targetStepId)
        {
            if (string.IsNullOrWhiteSpace(contextKey)) throw new ArgumentNullException(nameof(contextKey));

            return AddJumpCondition(
                (ctx, result) => ctx != null &&
                                 ctx.TryGetData<T>(contextKey, out var actualValue) &&
                                 EqualityComparer<T>.Default.Equals(actualValue, expectedValue),
                targetStepId);
        }

        public WorkflowStep AddJumpOnContextValueOnSuccess<T>(string contextKey, T expectedValue, string targetStepId)
        {
            if (string.IsNullOrWhiteSpace(contextKey)) throw new ArgumentNullException(nameof(contextKey));

            return AddJumpCondition(
                (ctx, result) => result == ActivityResult.Success &&
                                 ctx != null &&
                                 ctx.TryGetData<T>(contextKey, out var actualValue) &&
                                 EqualityComparer<T>.Default.Equals(actualValue, expectedValue),
                targetStepId);
        }

        public WorkflowStep AddJumpOnRouteValue<T>(string routeKey, T expectedValue, string targetStepId)
        {
            if (string.IsNullOrWhiteSpace(routeKey)) throw new ArgumentNullException(nameof(routeKey));

            return AddJumpCondition(
                (ctx, result) => ctx != null &&
                                 ctx.TryGetRoute<T>(routeKey, out var actualValue) &&
                                 EqualityComparer<T>.Default.Equals(actualValue, expectedValue),
                targetStepId);
        }

        public WorkflowStep AddJumpOnRouteValueOnSuccess<T>(string routeKey, T expectedValue, string targetStepId)
        {
            if (string.IsNullOrWhiteSpace(routeKey)) throw new ArgumentNullException(nameof(routeKey));

            return AddJumpCondition(
                (ctx, result) => result == ActivityResult.Success &&
                                 ctx != null &&
                                 ctx.TryGetRoute<T>(routeKey, out var actualValue) &&
                                 EqualityComparer<T>.Default.Equals(actualValue, expectedValue),
                targetStepId);
        }

        public WorkflowStep AddRouteBranchOnSuccess<T>(string routeKey, IDictionary<T, string> routeTargets)
        {
            if (string.IsNullOrWhiteSpace(routeKey)) throw new ArgumentNullException(nameof(routeKey));
            if (routeTargets == null) throw new ArgumentNullException(nameof(routeTargets));

            return AddDynamicJumpCondition(
                (ctx, result) => result == ActivityResult.Success && TryResolveRouteBranchTarget(ctx, routeKey, routeTargets, out var _),
                (ctx, result) => ResolveRouteBranchTarget(ctx, routeKey, routeTargets));
        }

        public WorkflowStep AddRouteBranch<T>(ActivityResult expectedResult, string routeKey, IDictionary<T, string> routeTargets)
        {
            if (string.IsNullOrWhiteSpace(routeKey)) throw new ArgumentNullException(nameof(routeKey));
            if (routeTargets == null) throw new ArgumentNullException(nameof(routeTargets));

            return AddDynamicJumpCondition(
                (ctx, result) => result == expectedResult && TryResolveRouteBranchTarget(ctx, routeKey, routeTargets, out var _),
                (ctx, result) => ResolveRouteBranchTarget(ctx, routeKey, routeTargets));
        }

        public WorkflowStep AddRouteJump(string routeContextKey = "WorkflowRoutes")
        {
            return AddDynamicJumpCondition(
                (ctx, result) => TryResolveRouteTarget(ctx, routeContextKey, out var _),
                (ctx, result) => ResolveRouteTarget(ctx, routeContextKey));
        }

        public WorkflowStep AddRouteJumpOnSuccess(string routeContextKey = "WorkflowRoutes")
        {
            return AddDynamicJumpCondition(
                (ctx, result) => result == ActivityResult.Success && TryResolveRouteTarget(ctx, routeContextKey, out var _),
                (ctx, result) => ResolveRouteTarget(ctx, routeContextKey));
        }

        // 可以添加更多方便的条件方法，例如：
        public WorkflowStep AddJumpOnSuccess(string targetStepId)
        {
            return AddJumpCondition((ctx, result) => result == ActivityResult.Success, targetStepId);
        }

        public WorkflowStep AddJumpOnFailure(string targetStepId)
        {
            return AddJumpCondition((ctx, result) => result == ActivityResult.Failure, targetStepId);
        }

        public WorkflowStep AddJumpOnCanceled(string targetStepId)
        {
            return AddJumpCondition((ctx, result) => result == ActivityResult.Canceled, targetStepId);
        }

        private bool TryResolveRouteTarget(WorkflowContext context, string routeContextKey, out string targetStepId)
        {
            if (context != null &&
                context.TryGetData<IDictionary<string, string>>(routeContextKey, out var routes) &&
                routes != null &&
                routes.TryGetValue(Id, out targetStepId) &&
                !string.IsNullOrWhiteSpace(targetStepId))
            {
                return true;
            }

            targetStepId = null;
            return false;
        }

        private string ResolveRouteTarget(WorkflowContext context, string routeContextKey)
        {
            if (TryResolveRouteTarget(context, routeContextKey, out var targetStepId))
            {
                return targetStepId;
            }

            throw new InvalidOperationException($"步骤 '{Id}' 未找到有效的路由目标。上下文键: '{routeContextKey}'。");
        }

        private bool TryResolveRouteBranchTarget<T>(WorkflowContext context, string routeKey, IDictionary<T, string> routeTargets, out string targetStepId)
        {
            if (context != null &&
                context.TryGetRoute<T>(routeKey, out var routeValue) &&
                routeTargets != null &&
                routeTargets.TryGetValue(routeValue, out targetStepId) &&
                !string.IsNullOrWhiteSpace(targetStepId))
            {
                return true;
            }

            targetStepId = null;
            return false;
        }

        private string ResolveRouteBranchTarget<T>(WorkflowContext context, string routeKey, IDictionary<T, string> routeTargets)
        {
            if (TryResolveRouteBranchTarget(context, routeKey, routeTargets, out var targetStepId))
            {
                return targetStepId;
            }

            throw new InvalidOperationException($"步骤 '{Id}' 未找到匹配的路由分支。路由键: '{routeKey}'。");
        }
    }

    /// <summary>
    /// 定义一个条件跳转规则。
    /// </summary>
    public class JumpCondition
    {
        public Func<WorkflowContext, ActivityResult, bool> Condition { get; } // 判断是否跳转的条件
        public string TargetStepId { get; } // 满足条件时跳转到的目标步骤ID
        private readonly Func<WorkflowContext, ActivityResult, string> _targetStepResolver;

        public JumpCondition(Func<WorkflowContext, ActivityResult, bool> condition, string targetStepId)
            : this(condition, (ctx, result) => targetStepId)
        {
            TargetStepId = targetStepId ?? throw new ArgumentNullException(nameof(targetStepId));
        }

        public JumpCondition(Func<WorkflowContext, ActivityResult, bool> condition, Func<WorkflowContext, ActivityResult, string> targetStepResolver)
        {
            Condition = condition ?? throw new ArgumentNullException(nameof(condition));
            _targetStepResolver = targetStepResolver ?? throw new ArgumentNullException(nameof(targetStepResolver));
        }

        public string ResolveTargetStepId(WorkflowContext context, ActivityResult result)
        {
            var targetStepId = _targetStepResolver(context, result);
            if (string.IsNullOrWhiteSpace(targetStepId))
            {
                throw new InvalidOperationException("跳转目标步骤ID不能为空。");
            }

            return targetStepId;
        }
    }
}