// Pure task-engine model (spec §3–§4): the task types and the duration formula. No lib/db
// imports — the frontend imports this for the live duration preview in the crew picker
// (same precedent as tech.ts / ship-costs.ts).
import { MISMATCH_CANCEL_TRAIT, PREFERRED_ROLES, TRAIT_DURATION_MODIFIERS, WORK_POINTS } from './crew-costs'
import type { CrewMember } from './crew'
import type { CrewDto, InventoryItemDto } from './save'
import { BUILD_PART_COST, expandCost, totalQty, upgradeCost } from './ship-costs'
import { TECHS } from './tech'

export type TaskType = 'JUMP' | 'EXPLORE' | 'SHIP_UPGRADE' | 'SHIP_EXPAND' | 'SHIP_BUILD' | 'RESEARCH'

export type TaskStatus = 'ACTIVE' | 'PENDING' | 'DONE'

// One queued/active/done action (spec §3). `payload` is a JSON string whose shape depends on
// the TaskType: JUMP {systemId, hops} · SHIP_UPGRADE/EXPAND {systemId} · SHIP_BUILD {type} ·
// RESEARCH {techId} · EXPLORE {planetId}.
export interface Task {
  id: number
  saveId: number
  type: TaskType
  payload: string
  leadCrewId: number
  helpers: number[]
  duration: number
  remaining: number
  status: TaskStatus
  queuedAtTurn: number
}

// Work points per action (spec §4): JUMP scales with hop count, the rest are flat.
function workPoints(type: TaskType, hopCount: number): number {
  switch (type) {
    case 'JUMP':
      return hopCount * WORK_POINTS.JUMP_PER_HOP
    case 'EXPLORE':
      return WORK_POINTS.EXPLORE
    case 'RESEARCH':
      return WORK_POINTS.RESEARCH
    default:
      return WORK_POINTS.SHIP_WORK // SHIP_UPGRADE | SHIP_EXPAND | SHIP_BUILD
  }
}

// One trait's modifier for a lead on an action type: its per-type entry plus the 'ANY' entry.
// Traits without a map entry contribute 0.
function traitModifier(trait: string, type: TaskType): number {
  const mods = TRAIT_DURATION_MODIFIERS[trait]
  if (!mods) return 0
  return (mods[type] ?? 0) + (mods['ANY'] ?? 0)
}

// duration = max(1, ceil(work / totalPower) + mismatchPenalty + traitModifierSum) — spec §4.
// totalPower = Σ powerOf over the WHOLE team (lead + helpers); the default powerOf is the
// constant 1 until PR B feeds the skill band. The mismatch penalty and the trait modifiers
// apply to the LEAD only — helpers contribute power, are never penalised, and their traits do
// not apply. `hopCount` is only meaningful for JUMP (pass 1 for the other types).
export function computeDuration(
  type: TaskType,
  hopCount: number,
  lead: CrewMember,
  helpers: CrewMember[],
  powerOf: (m: CrewMember) => number = () => 1,
): number {
  const totalPower = Math.max(1, [lead, ...helpers].reduce((sum, m) => sum + powerOf(m), 0))
  const mismatchPenalty = lead.traitGood === MISMATCH_CANCEL_TRAIT || PREFERRED_ROLES[type].includes(lead.role) ? 0 : 1
  const traitModifierSum = traitModifier(lead.traitGood, type) + traitModifier(lead.traitBad, type)
  return Math.max(1, Math.ceil(workPoints(type, hopCount) / totalPower) + mismatchPenalty + traitModifierSum)
}

// --- Queueing: validation + row construction (pure, no DB) -------------------------------
//
// queueTask runs over a plain snapshot of the save (QueueState) and decides whether a new
// task can be queued and what row it becomes. Pure like crew.ts / ship-costs.ts — the route
// (a later task) maps schema rows into QueueState, calls queueTask, and persists the result:
// insert the task row (adding `id` + `saveId` at the DB boundary) and the deducted hold.

// Carries an HTTP status so route handlers can map failures to responses without re-parsing
// (same pattern as JumpError / ShipError / ResearchError / ExploreError).
export class TaskError extends Error {
  constructor(
    public readonly status: number,
    message: string,
  ) {
    super(message)
  }
}

// The queueing request — the existing endpoints' bodies plus the crew team. Payload field
// names follow the routes (the spec's names differ):
//   JUMP { systemId, hops }  — the route computes `hops` with jumpToSystem's logic
//   (reachableWithin + NAV AI) and passes it in; the body field is `systemId`, not `toSystemId`
//   EXPLORE { planetId }
//   SHIP_UPGRADE { systemId } · SHIP_EXPAND { systemId } · SHIP_BUILD { type }
//   RESEARCH { techId }      — the tech row's id, not the slug
export interface QueueTaskRequest {
  type: TaskType
  payload: Record<string, unknown>
  leadCrewId: number
  helperCrewIds: number[]
}

// Plain per-save snapshot the decision runs over — the route maps schema rows into these
// (same row↔domain boundary as the tasks table in save.ts).
export interface QueueState {
  turn: number
  crew: CrewDto[]
  tasks: Task[]
  inventory: InventoryItemDto[] // cargo hold, id order (oldest first)
  shipSystems: { id: number; type: string; level: number; capacity: number }[] // UPGRADE/EXPAND costs scale with the target's current level/capacity
  tech: { id: number; slug: string }[] // RESEARCH cost comes from the matching TECHS def, like research.ts
}

// The new row minus the two values only the DB boundary knows: `id` (autoincrement) and
// `saveId` (filled in by save.ts's row↔Task mapping on insert).
export interface QueueResult {
  task: Omit<Task, 'id' | 'saveId'>
  inventory: InventoryItemDto[] // unchanged for JUMP/EXPLORE; deducted for SHIP_* / RESEARCH
}

// Queue a task. Validation order: unknown crew (404) → busy (409) → in transit (409, all
// types) → second jump (409) → cost (422, SHIP_* / RESEARCH only). Never advances the turn.
export function queueTask(state: QueueState, req: QueueTaskRequest): QueueResult {
  const lead = state.crew.find((c) => c.id === req.leadCrewId)
  if (!lead) throw new TaskError(404, `Unknown crew member ${req.leadCrewId}`)
  const helpers: CrewDto[] = []
  for (const id of req.helperCrewIds) {
    const helper = state.crew.find((c) => c.id === id)
    if (!helper) throw new TaskError(404, `Unknown crew member ${id}`)
    helpers.push(helper)
  }

  // Busy (409). Spec §3: one ACTIVE task per crew member, and a lead may chain one PENDING
  // task behind it (FIFO — auto-starts when the current one completes). So: any crew member
  // committed to a PENDING task is blocked; a helper on an ACTIVE task is blocked; a lead on
  // an ACTIVE task passes and the new task is queued PENDING behind it.
  const inStatus = (id: number, status: TaskStatus) => state.tasks.some((t) => t.status === status && (t.leadCrewId === id || t.helpers.includes(id)))
  const checkBusy = (c: CrewDto, isLead: boolean) => {
    if (inStatus(c.id, 'PENDING')) throw new TaskError(409, `${c.name} is already committed to a pending task`)
    if (!isLead && inStatus(c.id, 'ACTIVE')) throw new TaskError(409, `${c.name} is already busy`)
  }
  checkBusy(lead, true)
  for (const helper of helpers) checkBusy(helper, false)

  // In transit (409): while any JUMP is ACTIVE, no new tasks of any type (spec §3).
  const jumps = state.tasks.filter((t) => t.type === 'JUMP')
  if (jumps.some((t) => t.status === 'ACTIVE')) throw new TaskError(409, 'A jump is in transit — no new tasks can be queued')
  // Only one JUMP at a time, active or pending (two arrivals could never resolve on one tick).
  // The ACTIVE half is already caught above, so this fires on a pending jump.
  if (req.type === 'JUMP' && jumps.some((t) => t.status !== 'DONE')) throw new TaskError(409, 'A jump is already queued')

  // Costs deduct at queue time (spec §3) — the existing cost logic from ship-costs.ts /
  // tech.ts and spendItems' 422. JUMP/EXPLORE have no resource cost. Target existence and
  // the 409 gates (max level / capacity, not built, already built, build gate, tech prereqs)
  // stay in the routes with their existing codes — the route resolves ids before calling.
  let inventory = state.inventory
  if (req.type === 'SHIP_UPGRADE' || req.type === 'SHIP_EXPAND') {
    const system = state.shipSystems.find((s) => s.id === req.payload.systemId)!
    inventory = deduct(inventory, 'resource', req.type === 'SHIP_UPGRADE' ? upgradeCost(system.level) : expandCost(system.capacity))
  } else if (req.type === 'SHIP_BUILD') {
    inventory = deduct(inventory, 'part', BUILD_PART_COST)
  } else if (req.type === 'RESEARCH') {
    const def = TECHS.find((t) => t.slug === state.tech.find((r) => r.id === req.payload.techId)?.slug)!
    inventory = deduct(inventory, def.costKind, def.costQty)
  }

  // Success: duration from the Task-1 formula, status from what the team is doing right now.
  // A crew member is "free" when on no ACTIVE/PENDING task; after the checks above only a
  // lead chaining behind its own ACTIVE can be non-free.
  const free = (id: number) => !inStatus(id, 'ACTIVE') && !inStatus(id, 'PENDING')
  const hops = req.type === 'JUMP' ? (req.payload.hops as number) : 0
  const duration = computeDuration(req.type, hops, lead, helpers)
  const status: TaskStatus = [lead, ...helpers].every((c) => free(c.id)) ? 'ACTIVE' : 'PENDING'

  return {
    task: {
      type: req.type,
      payload: JSON.stringify(req.payload),
      leadCrewId: req.leadCrewId,
      helpers: req.helperCrewIds,
      duration,
      remaining: duration,
      status,
      queuedAtTurn: state.turn, // queueing is free — the turn advances only on the tick
    },
    inventory,
  }
}

// Pure version of spendItems' consumption (lib/game/ship.ts): the total is checked up front
// (shortfall → the same 422 spendItems throws), then the oldest rows first (array order = id
// order); rows that hit zero are dropped. The input array is never mutated.
function deduct(items: InventoryItemDto[], kind: 'resource' | 'part', amount: number): InventoryItemDto[] {
  if (totalQty(items, kind) < amount) {
    throw new TaskError(422, `Insufficient ${kind === 'resource' ? 'resources' : 'parts'} in the cargo hold — need ${amount}`)
  }
  let remaining = amount
  const out: InventoryItemDto[] = []
  for (const item of items) {
    if (item.kind !== kind) {
      out.push(item)
      continue
    }
    const take = Math.min(item.qty, remaining)
    remaining -= take
    if (take < item.qty) out.push({ ...item, qty: item.qty - take })
  }
  return out
}

// --- The turn tick: decrement, resolve, FIFO auto-start (pure — no DB) -------------------
//
// tickTurn is the whole §3 tick over the same plain QueueState queueTask consumes. It owns
// the turn increment and nothing else: it applies no effect and runs no mission logic —
// the save.ts orchestrator (runTurn) calls the 4a resolvers for the returned `completed`
// tasks, in the order returned.
export interface TickResult {
  turn: number // state.turn + 1 — the tick IS the turn increment
  tasks: Task[] // every task, updated: ACTIVE decremented, finished → DONE, started PENDING → ACTIVE
  completed: Task[] // the tasks that hit 0 this tick, in resolution order
}

const byQueueOrder = (a: Task, b: Task) => a.queuedAtTurn - b.queuedAtTurn || a.id - b.id

export function tickTurn(state: QueueState): TickResult {
  const turn = state.turn + 1
  const tasks = state.tasks.map((t) => ({ ...t })) // never mutate the input (house style — deduct)

  // (a) every ACTIVE task ages by one; PENDING/DONE rows do not age.
  for (const t of tasks) if (t.status === 'ACTIVE') t.remaining -= 1

  // (b) everything that hit 0 resolves this tick. Marking DONE frees the whole team
  // (busyness is derived from the tasks table — there is no crew status column to update).
  // <= 0, not === 0: a corrupt row at or below zero still completes on the next tick
  // instead of dead-ending the queue (spec focus 4: no dead ends).
  const completed = tasks
    .filter((t) => t.status === 'ACTIVE' && t.remaining <= 0)
    .sort(byQueueOrder)
  for (const t of completed) t.status = 'DONE'

  // (c) auto-start: ONE forward pass over PENDING in (queuedAtTurn ASC, id ASC). A task starts
  // (PENDING → ACTIVE, remaining unchanged — it keeps its full duration; its first decrement
  // lands on the next tick) when its FULL team (lead + all helpers) is free: no member on an
  // ACTIVE task, and no member committed to an EARLIER (queuedAtTurn, id) PENDING that is still
  // pending. A member on a LATER PENDING does not block — this task has first claim, and once
  // started it holds that member via the ACTIVE clause, blocking the later PENDING in the same
  // pass. Under queueTask's invariants (one PENDING per member) the PENDING clause only bites
  // on admin-corrupted rows, where it keeps the pass deterministic: of a contested member's
  // PENDINGs the earliest (queuedAtTurn, id) always gets first claim, so at most ONE of their
  // PENDINGs starts per tick (the FIFO chain of spec §3), and no PENDING starves behind a peer.
  // A start only makes its team busier — never frees anyone — so a task that cannot start at
  // its position cannot start later in the same pass: one pass is complete.
  for (const t of tasks.filter((t) => t.status === 'PENDING').sort(byQueueOrder)) {
    const free = (id: number) =>
      !tasks.some((o) => o.status === 'ACTIVE' && (o.leadCrewId === id || o.helpers.includes(id))) &&
      !tasks.some((o) => o.status === 'PENDING' && o.id !== t.id && byQueueOrder(o, t) < 0 && (o.leadCrewId === id || o.helpers.includes(id)))
    if ([t.leadCrewId, ...t.helpers].every(free)) t.status = 'ACTIVE'
  }

  return { turn, tasks, completed }
}