/**
 * Flow simulation engine — pure function, no React dependencies.
 *
 * Replaces the random-noise simulation with actual flow logic:
 *   inflow → overflow distribution → spending drain → outcome accumulation
 */

import type { FlowNode, FunnelNodeData, OutcomeNodeData, SourceNodeData } from './types'

export interface SimulationConfig {
  tickDivisor: number        // inflowRate divided by this per tick
  spendingRateHealthy: number  // drain multiplier in healthy zone
  spendingRateOverflow: number // drain multiplier above maxThreshold
  spendingRateCritical: number // drain multiplier below minThreshold
}

export const DEFAULT_CONFIG: SimulationConfig = {
  tickDivisor: 10,
  spendingRateHealthy: 0.5,
  spendingRateOverflow: 0.8,
  spendingRateCritical: 0.1,
}

export function simulateTick(
  nodes: FlowNode[],
  config: SimulationConfig = DEFAULT_CONFIG,
): FlowNode[] {
  const { tickDivisor, spendingRateHealthy, spendingRateOverflow, spendingRateCritical } = config

  // Separate funnels (sorted top-to-bottom) from outcomes
  const funnelNodes = nodes
    .filter((n) => n.type === 'funnel')
    .sort((a, b) => a.position.y - b.position.y)

  // Source nodes: sum allocations into funnel inflow
  const sourceInflow = new Map<string, number>()
  nodes.forEach((node) => {
    if (node.type !== 'source') return
    const data = node.data as SourceNodeData
    for (const alloc of data.targetAllocations) {
      const share = (data.flowRate / tickDivisor) * (alloc.percentage / 100)
      sourceInflow.set(alloc.targetId, (sourceInflow.get(alloc.targetId) ?? 0) + share)
    }
  })

  // Accumulators for inter-node transfers
  const overflowIncoming = new Map<string, number>()
  const spendingIncoming = new Map<string, number>()

  // Store updated funnel data
  const updatedFunnels = new Map<string, FunnelNodeData>()

  for (const node of funnelNodes) {
    const src = node.data as FunnelNodeData
    const data: FunnelNodeData = { ...src }

    // 1. Natural inflow + source node inflow
    let value = data.currentValue + data.inflowRate / tickDivisor + (sourceInflow.get(node.id) ?? 0)

    // 2. Overflow received from upstream funnels
    value += overflowIncoming.get(node.id) ?? 0

    // 3. Cap at maxCapacity
    value = Math.min(value, data.maxCapacity)

    // 4. Distribute overflow when above maxThreshold
    if (value > data.maxThreshold && data.overflowAllocations.length > 0) {
      const excess = value - data.maxThreshold
      for (const alloc of data.overflowAllocations) {
        const share = excess * (alloc.percentage / 100)
        overflowIncoming.set(
          alloc.targetId,
          (overflowIncoming.get(alloc.targetId) ?? 0) + share,
        )
      }
      value = data.maxThreshold
    }

    // 5. Spending drain (gated by zone)
    if (value > 0 && data.spendingAllocations.length > 0) {
      let rateMultiplier: number
      if (value > data.maxThreshold) {
        rateMultiplier = spendingRateOverflow
      } else if (value >= data.minThreshold) {
        rateMultiplier = spendingRateHealthy
      } else {
        rateMultiplier = spendingRateCritical
      }

      let drain = (data.inflowRate / tickDivisor) * rateMultiplier
      drain = Math.min(drain, value) // cannot drain below 0

      value -= drain

      for (const alloc of data.spendingAllocations) {
        const share = drain * (alloc.percentage / 100)
        spendingIncoming.set(
          alloc.targetId,
          (spendingIncoming.get(alloc.targetId) ?? 0) + share,
        )
      }
    }

    data.currentValue = Math.max(0, value)
    updatedFunnels.set(node.id, data)
  }

  // Rebuild node array with updated data
  return nodes.map((node) => {
    if (node.type === 'funnel' && updatedFunnels.has(node.id)) {
      return { ...node, data: updatedFunnels.get(node.id)! }
    }

    if (node.type === 'outcome') {
      const data = node.data as OutcomeNodeData
      const incoming = spendingIncoming.get(node.id) ?? 0
      if (incoming <= 0) return node

      const newReceived = Math.min(
        data.fundingTarget > 0 ? data.fundingTarget * 1.05 : Infinity,
        data.fundingReceived + incoming,
      )

      let newStatus = data.status
      if (newStatus === 'blocked') {
        // Don't auto-change blocked status
      } else if (data.phases && data.phases.length > 0) {
        // Phase-aware status
        const anyUnlocked = data.phases.some(p => newReceived >= p.fundingThreshold)
        const allUnlocked = data.phases.every(p => newReceived >= p.fundingThreshold)
        const allTasksDone = data.phases.every(p => p.tasks.every(t => t.completed))

        if (allUnlocked && allTasksDone) {
          newStatus = 'completed'
        } else if (anyUnlocked) {
          newStatus = 'in-progress'
        }
      } else {
        // Fallback: no phases defined
        if (data.fundingTarget > 0 && newReceived >= data.fundingTarget) {
          newStatus = 'completed'
        } else if (newReceived > 0 && newStatus === 'not-started') {
          newStatus = 'in-progress'
        }
      }

      return {
        ...node,
        data: { ...data, fundingReceived: newReceived, status: newStatus },
      }
    }

    return node
  })
}