import { z } from 'zod'
import { TRPCError } from '@trpc/server'
import { Prisma } from '@prisma/client'
import { router, adminProcedure } from '../trpc'
import { logAudit } from '@/server/utils/audit'
import {
  previewRouting,
  evaluateRoutingRules,
  executeRouting,
} from '@/server/services/routing-engine'

export const routingRouter = router({
  /**
   * Preview routing: show where projects would land without executing.
   * Delegates to routing-engine service for proper predicate evaluation.
   */
  preview: adminProcedure
    .input(
      z.object({
        pipelineId: z.string(),
        projectIds: z.array(z.string()).min(1).max(500),
      })
    )
    .mutation(async ({ ctx, input }) => {
      const results = await previewRouting(
        input.projectIds,
        input.pipelineId,
        ctx.prisma
      )

      return {
        pipelineId: input.pipelineId,
        totalProjects: results.length,
        results: results.map((r) => ({
          projectId: r.projectId,
          projectTitle: r.projectTitle,
          matchedRuleId: r.matchedRule?.ruleId ?? null,
          matchedRuleName: r.matchedRule?.ruleName ?? null,
          targetTrackId: r.matchedRule?.destinationTrackId ?? null,
          targetTrackName: null as string | null,
          targetStageId: r.matchedRule?.destinationStageId ?? null,
          targetStageName: null as string | null,
          routingMode: r.matchedRule?.routingMode ?? null,
          reason: r.reason,
        })),
      }
    }),

  /**
   * Execute routing: evaluate rules and move projects into tracks/stages.
   * Delegates to routing-engine service which enforces PARALLEL/EXCLUSIVE/POST_MAIN modes.
   */
  execute: adminProcedure
    .input(
      z.object({
        pipelineId: z.string(),
        projectIds: z.array(z.string()).min(1).max(500),
      })
    )
    .mutation(async ({ ctx, input }) => {
      // Verify pipeline is ACTIVE
      const pipeline = await ctx.prisma.pipeline.findUniqueOrThrow({
        where: { id: input.pipelineId },
      })

      if (pipeline.status !== 'ACTIVE') {
        throw new TRPCError({
          code: 'PRECONDITION_FAILED',
          message: 'Pipeline must be ACTIVE to route projects',
        })
      }

      // Load projects to get their current active stage states
      const projects = await ctx.prisma.project.findMany({
        where: { id: { in: input.projectIds } },
        select: {
          id: true,
          title: true,
          projectStageStates: {
            where: { exitedAt: null },
            select: { stageId: true },
            take: 1,
          },
        },
      })

      if (projects.length === 0) {
        throw new TRPCError({
          code: 'NOT_FOUND',
          message: 'No matching projects found',
        })
      }

      let routedCount = 0
      let skippedCount = 0
      const errors: Array<{ projectId: string; error: string }> = []

      for (const project of projects) {
        const activePSS = project.projectStageStates[0]
        if (!activePSS) {
          skippedCount++
          continue
        }

        // Evaluate routing rules using the service
        const matchedRule = await evaluateRoutingRules(
          project.id,
          activePSS.stageId,
          input.pipelineId,
          ctx.prisma
        )

        if (!matchedRule) {
          skippedCount++
          continue
        }

        // Execute routing using the service (handles PARALLEL/EXCLUSIVE/POST_MAIN)
        const result = await executeRouting(
          project.id,
          matchedRule,
          ctx.user.id,
          ctx.prisma
        )

        if (result.success) {
          routedCount++
        } else {
          skippedCount++
          if (result.errors?.length) {
            errors.push({ projectId: project.id, error: result.errors[0] })
          }
        }
      }

      // Record batch-level audit log
      await logAudit({
        prisma: ctx.prisma,
        userId: ctx.user.id,
        action: 'ROUTING_EXECUTED',
        entityType: 'Pipeline',
        entityId: input.pipelineId,
        detailsJson: {
          projectCount: projects.length,
          routedCount,
          skippedCount,
          errors: errors.length > 0 ? errors : undefined,
        },
        ipAddress: ctx.ip,
        userAgent: ctx.userAgent,
      })

      return { routedCount, skippedCount, totalProjects: projects.length }
    }),

  /**
   * List routing rules for a pipeline
   */
  listRules: adminProcedure
    .input(z.object({ pipelineId: z.string() }))
    .query(async ({ ctx, input }) => {
      return ctx.prisma.routingRule.findMany({
        where: { pipelineId: input.pipelineId },
        orderBy: [{ isActive: 'desc' }, { priority: 'desc' }],
        include: {
          sourceTrack: { select: { id: true, name: true } },
          destinationTrack: { select: { id: true, name: true } },
        },
      })
    }),

  /**
   * Create or update a routing rule
   */
  upsertRule: adminProcedure
    .input(
      z.object({
        id: z.string().optional(), // If provided, update existing
        pipelineId: z.string(),
        name: z.string().min(1).max(255),
        scope: z.enum(['global', 'track', 'stage']).default('global'),
        sourceTrackId: z.string().optional().nullable(),
        destinationTrackId: z.string(),
        destinationStageId: z.string().optional().nullable(),
        predicateJson: z.record(z.unknown()),
        priority: z.number().int().min(0).max(1000).default(0),
        isActive: z.boolean().default(true),
      })
    )
    .mutation(async ({ ctx, input }) => {
      const { id, predicateJson, ...data } = input

      // Verify destination track exists in this pipeline
      const destTrack = await ctx.prisma.track.findFirst({
        where: { id: input.destinationTrackId, pipelineId: input.pipelineId },
      })
      if (!destTrack) {
        throw new TRPCError({
          code: 'BAD_REQUEST',
          message: 'Destination track must belong to the same pipeline',
        })
      }

      if (id) {
        // Update existing rule
        const rule = await ctx.prisma.$transaction(async (tx) => {
          const updated = await tx.routingRule.update({
            where: { id },
            data: {
              ...data,
              predicateJson: predicateJson as Prisma.InputJsonValue,
            },
          })

          await logAudit({
            prisma: tx,
            userId: ctx.user.id,
            action: 'UPDATE',
            entityType: 'RoutingRule',
            entityId: id,
            detailsJson: { name: input.name, priority: input.priority },
            ipAddress: ctx.ip,
            userAgent: ctx.userAgent,
          })

          return updated
        })

        return rule
      } else {
        // Create new rule
        const rule = await ctx.prisma.$transaction(async (tx) => {
          const created = await tx.routingRule.create({
            data: {
              ...data,
              predicateJson: predicateJson as Prisma.InputJsonValue,
            },
          })

          await logAudit({
            prisma: tx,
            userId: ctx.user.id,
            action: 'CREATE',
            entityType: 'RoutingRule',
            entityId: created.id,
            detailsJson: { name: input.name, priority: input.priority },
            ipAddress: ctx.ip,
            userAgent: ctx.userAgent,
          })

          return created
        })

        return rule
      }
    }),

  /**
   * Delete a routing rule
   */
  deleteRule: adminProcedure
    .input(
      z.object({
        id: z.string(),
      })
    )
    .mutation(async ({ ctx, input }) => {
      const existing = await ctx.prisma.routingRule.findUniqueOrThrow({
        where: { id: input.id },
        select: { id: true, name: true, pipelineId: true },
      })

      await ctx.prisma.$transaction(async (tx) => {
        await tx.routingRule.delete({
          where: { id: input.id },
        })

        await logAudit({
          prisma: tx,
          userId: ctx.user.id,
          action: 'DELETE',
          entityType: 'RoutingRule',
          entityId: input.id,
          detailsJson: { name: existing.name, pipelineId: existing.pipelineId },
          ipAddress: ctx.ip,
          userAgent: ctx.userAgent,
        })
      })

      return { success: true }
    }),

  /**
   * Reorder routing rules by priority (highest first)
   */
  reorderRules: adminProcedure
    .input(
      z.object({
        pipelineId: z.string(),
        orderedIds: z.array(z.string()).min(1),
      })
    )
    .mutation(async ({ ctx, input }) => {
      const rules = await ctx.prisma.routingRule.findMany({
        where: { pipelineId: input.pipelineId },
        select: { id: true },
      })
      const ruleIds = new Set(rules.map((rule) => rule.id))

      for (const id of input.orderedIds) {
        if (!ruleIds.has(id)) {
          throw new TRPCError({
            code: 'BAD_REQUEST',
            message: `Routing rule ${id} does not belong to this pipeline`,
          })
        }
      }

      await ctx.prisma.$transaction(async (tx) => {
        const maxPriority = input.orderedIds.length
        await Promise.all(
          input.orderedIds.map((id, index) =>
            tx.routingRule.update({
              where: { id },
              data: {
                priority: maxPriority - index,
              },
            })
          )
        )

        await logAudit({
          prisma: tx,
          userId: ctx.user.id,
          action: 'UPDATE',
          entityType: 'Pipeline',
          entityId: input.pipelineId,
          detailsJson: {
            action: 'ROUTING_RULES_REORDERED',
            ruleCount: input.orderedIds.length,
          },
          ipAddress: ctx.ip,
          userAgent: ctx.userAgent,
        })
      })

      return { success: true }
    }),

  /**
   * Toggle a routing rule on/off
   */
  toggleRule: adminProcedure
    .input(
      z.object({
        id: z.string(),
        isActive: z.boolean(),
      })
    )
    .mutation(async ({ ctx, input }) => {
      const rule = await ctx.prisma.$transaction(async (tx) => {
        const updated = await tx.routingRule.update({
          where: { id: input.id },
          data: { isActive: input.isActive },
        })

        await logAudit({
          prisma: tx,
          userId: ctx.user.id,
          action: input.isActive ? 'ROUTING_RULE_ENABLED' : 'ROUTING_RULE_DISABLED',
          entityType: 'RoutingRule',
          entityId: input.id,
          detailsJson: { isActive: input.isActive, name: updated.name },
          ipAddress: ctx.ip,
          userAgent: ctx.userAgent,
        })

        return updated
      })

      return rule
    }),
})