import { eq } from 'drizzle-orm'
import type { GameDb } from '@/lib/db/client'
import { persist } from '@/lib/db/client'
import * as schema from '@/lib/db/schema'
import { generateStartingCrew, rollCrewMember, startingCrewRng, type CrewMember } from './crew'
import { BASE_CAPACITY, BASE_LEVEL, SHIP_TYPES } from './ship-costs'
import { checkMissionCompletion, topUpMissionBoard } from './missions'
import { TECHS } from './tech'
import { bodyRng, explorationRng, generatePlanets, generateRing, generateStartRegion, mulberry32, rollExploration, type FoundItem } from './world'

// Save lifecycle: auto-init on first hit, world state reads, and the jump action.
// Single-player by design — exactly one save row ever exists, so every query below is
// unscoped (there is nothing to scope against).

export interface WorldSystemDto {
  id: number
  name: string
  x: number
  y: number
  discovered: boolean
  current: boolean
}

export interface WorldState {
  systems: WorldSystemDto[]
  edges: [number, number][] // undirected system-id pairs, deduped + sorted for stable output
  turn: number
}

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

function newSeed(): string {
  const buf = new Uint32Array(1)
  crypto.getRandomValues(buf)
  return String(buf[0])
}

// Deterministic per save+turn: the whole world of a seed is reproducible from (seed, turn).
function expansionRng(seed: string, turn: number): () => number {
  return mulberry32((Number(seed) + turn * 1_000_003) >>> 0)
}

// The bodies of one system (planets + moons), derived from (seed, system id) via bodyRng —
// independent of generation order and every other system. Shared by new-game creation and the
// v2 backfill so both produce identical rows for a given save+system.
async function insertBodiesForSystem(db: GameDb, systemId: number, seed: string): Promise<void> {
  for (const body of generatePlanets(bodyRng(seed, systemId))) {
    const [planet] = await db.db.insert(schema.planets).values({ systemId, parentId: null, name: body.name, type: body.type, hazard: body.hazard }).returning({ id: schema.planets.id })
    for (const moon of body.moons) {
      await db.db.insert(schema.planets).values({ systemId, parentId: planet.id, name: moon.name, type: moon.type, hazard: moon.hazard })
    }
  }
}

// Inserts one system together with its generated bodies, so a system is never left without
// worlds to explore.
async function insertSystemWithBodies(db: GameDb, saveId: number, ws: { name: string; x: number; y: number }, seed: string): Promise<number> {
  const [row] = await db.db.insert(schema.solarSystems).values({ saveId, name: ws.name, x: ws.x, y: ws.y }).returning({ id: schema.solarSystems.id })
  await insertBodiesForSystem(db, row.id, seed)
  return row.id
}

// v2 backfill: every system without planets gets its generated bodies. Idempotent — systems
// that already have rows are skipped, so a second run changes nothing.
async function ensureBodiesForAllSystems(db: GameDb, saveId: number, seed: string): Promise<void> {
  const systems = await db.db.select().from(schema.solarSystems)
  for (const system of systems) {
    const rows = await db.db.select({ id: schema.planets.id }).from(schema.planets).where(eq(schema.planets.systemId, system.id))
    if (rows.length === 0) await insertBodiesForSystem(db, system.id, seed)
  }
}

async function insertRoutes(db: GameDb, edges: [number, number][], resolve: (index: number) => number): Promise<void> {
  for (const [a, b] of edges) {
    const from = resolve(a)
    const to = resolve(b)
    await db.db.insert(schema.jumpRoutes).values({ fromSystem: from, toSystem: to })
    await db.db.insert(schema.jumpRoutes).values({ fromSystem: to, toSystem: from }) // both directions → adjacency is a single-row lookup
  }
}

// Seeds the starting crew for a fresh save: 2–3 members derived from the seed alone.
async function seedStartingCrew(db: GameDb, saveId: number, seed: string): Promise<void> {
  for (const member of generateStartingCrew(startingCrewRng(seed))) {
    await db.db.insert(schema.crew).values({ saveId, name: member.name, role: member.role, traitGood: member.traitGood, traitBad: member.traitBad, origin: 'STARTING CREW' })
  }
}

// What each schema version added to a save. Saves created by older code lack the data newer
// versions seed at new-game time, so ensureSave runs these steps in order for anything below
// current — each step is idempotent (a no-op when its data already exists).
export const SCHEMA_VERSION = 6 // v1: save + start region only · v2: bodies for every system · v3: starting crew · v4: starting ship · v5: tech tree · v6: mission board

// Seeds the starting ship: one row per known type — core types built at base values, the rest
// unbuilt (level/capacity 0) until a BUILD action.
async function seedStartingShip(db: GameDb, saveId: number): Promise<void> {
  for (const def of SHIP_TYPES) {
    await db.db.insert(schema.shipSystems).values({ saveId, type: def.type, level: def.builtAtStart ? BASE_LEVEL : 0, capacity: def.builtAtStart ? BASE_CAPACITY : 0 })
  }
}

// Seeds the tech tree: one row per known tech (definitions from lib/game/tech.ts), none researched.
async function seedStartingTech(db: GameDb, saveId: number): Promise<void> {
  for (const def of TECHS) {
    await db.db.insert(schema.tech).values({ saveId, slug: def.slug, name: def.name, costKind: def.costKind, costQty: def.costQty, prerequisites: def.prereqs.join(','), effect: def.effect })
  }
}

// Creates the save + starting region when the DB has none; backfills older saves otherwise.
// Safe to call on every request (single player, one process: check-then-insert cannot race).
export async function ensureSave(db: GameDb): Promise<void> {
  const existing = await db.db.select().from(schema.saves).limit(1)
  if (existing.length === 0) {
    await createNewGame(db)
    return
  }
  await backfillSave(db, existing[0])
}

async function createNewGame(db: GameDb): Promise<void> {
  const seed = newSeed()
  const region = generateStartRegion(mulberry32(Number(seed)))
  const nowIso = new Date().toISOString()

  const [save] = await db.db.insert(schema.saves).values({ seed, turn: 0, createdAt: nowIso, schemaVersion: SCHEMA_VERSION }).returning()
  // All inserted as undiscovered first; the start is then marked discovered + current.
  const startId = await insertSystemWithBodies(db, save.id, region.start, seed)
  const neighborIds: number[] = []
  for (const n of region.neighbors) neighborIds.push(await insertSystemWithBodies(db, save.id, n, seed))
  await db.db.update(schema.solarSystems).set({ discovered: true, isCurrent: true }).where(eq(schema.solarSystems.id, startId))

  const resolve = (index: number) => (index === 0 ? startId : neighborIds[index - 1])
  await insertRoutes(db, region.edges, resolve)
  await seedStartingCrew(db, save.id, seed)
  await seedStartingShip(db, save.id)
  await seedStartingTech(db, save.id)
  await topUpMissionBoard(db) // only the start system is discovered yet — no DELIVER targets on a fresh game

  await db.db.insert(schema.events).values({ saveId: save.id, turn: 0, type: 'new_game', message: `New game — seed ${seed}, starting system ${region.start.name}`, createdAt: nowIso })
  await persist(db)
}

// Ordered idempotent backfill for a save created by older code. A NULL version means v1.
async function backfillSave(db: GameDb, save: { id: number; seed: string; schemaVersion: number | null }): Promise<void> {
  const from = save.schemaVersion ?? 1
  let version = from

  if (version < 2) {
    await ensureBodiesForAllSystems(db, save.id, save.seed) // bodies derive from (seed, system id) — identical to fresh generation
    version = 2
  }
  if (version < 3) {
    if ((await db.db.select().from(schema.crew)).length === 0) await seedStartingCrew(db, save.id, save.seed)
    version = 3
  }
  if (version < 4) {
    if ((await db.db.select().from(schema.shipSystems)).length === 0) await seedStartingShip(db, save.id)
    version = 4
  }
  if (version < 5) {
    if ((await db.db.select().from(schema.tech)).length === 0) await seedStartingTech(db, save.id)
    version = 5
  }
  if (version < 6) {
    await topUpMissionBoard(db) // idempotent — only inserts when fewer than MIN_AVAILABLE AVAILABLE contracts exist
    version = 6
  }

  if (from !== SCHEMA_VERSION) {
    await db.db.update(schema.saves).set({ schemaVersion: version }).where(eq(schema.saves.id, save.id))
    await persist(db)
  }
}

export async function getWorldState(db: GameDb): Promise<WorldState> {
  await ensureSave(db)
  const [save] = await db.db.select().from(schema.saves).limit(1)
  const systems = await db.db.select().from(schema.solarSystems)
  const routes = await db.db.select().from(schema.jumpRoutes)

  // Dedupe the stored directed pairs into sorted undirected edges.
  const seen = new Set<string>()
  const edges: [number, number][] = []
  for (const r of routes) {
    const a = Math.min(r.fromSystem, r.toSystem)
    const b = Math.max(r.fromSystem, r.toSystem)
    const key = `${a}-${b}`
    if (!seen.has(key)) {
      seen.add(key)
      edges.push([a, b])
    }
  }

  return {
    systems: systems.map((s) => ({ id: s.id, name: s.name, x: s.x, y: s.y, discovered: s.discovered, current: s.isCurrent })),
    edges,
    turn: save.turn,
  }
}

export async function jumpToSystem(db: GameDb, systemId: number): Promise<WorldState> {
  await ensureSave(db)
  const [save] = await db.db.select().from(schema.saves).limit(1)
  const systems = await db.db.select().from(schema.solarSystems)

  const target = systems.find((s) => s.id === systemId)
  if (!target) throw new JumpError(404, `Unknown system ${systemId}`)
  const current = systems.find((s) => s.isCurrent)!
  if (current.id === target.id) throw new JumpError(409, 'Already at this system')

  const routes = await db.db.select().from(schema.jumpRoutes)
  const adjacent = routes.some((r) => r.fromSystem === current.id && r.toSystem === target.id)
  if (!adjacent) throw new JumpError(409, `${target.name} is not reachable from ${current.name}`)

  const turn = save.turn + 1
  await db.db.update(schema.solarSystems).set({ isCurrent: false }).where(eq(schema.solarSystems.id, current.id))
  await db.db.update(schema.solarSystems).set({ isCurrent: true, discovered: true }).where(eq(schema.solarSystems.id, target.id))

  if (!target.discovered) {
    // Growing the chart: a ring of new (undiscovered) neighbours around the newly reached
    // system, so there is always somewhere to jump next and a route back.
    const rng = expansionRng(save.seed, turn)
    const takenNames = new Set(systems.map((s) => s.name))
    const ring = generateRing(rng, target.x, target.y, takenNames, systems)
    const ringIds: number[] = []
    for (const s of ring.systems) ringIds.push(await insertSystemWithBodies(db, save.id, s, save.seed))
    const resolve = (index: number) => (index === 0 ? target.id : ringIds[index - 1])
    await insertRoutes(db, ring.edges, resolve)
  }

  await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
  await db.db.insert(schema.events).values({ saveId: save.id, turn, type: 'jump', message: `Jumped to ${target.name}`, createdAt: new Date().toISOString() })
  await checkMissionCompletion(db, save.id, turn, { jumpedTo: target.id }) // an ACTIVE DELIVER may have arrived at its destination
  await topUpMissionBoard(db)
  await persist(db)

  return getWorldState(db)
}

// --- Local system + exploration ---------------------------------------------

export interface PlanetDto {
  id: number
  name: string
  type: string
  hazard: boolean
  explored: boolean
  parent: number | null // NULL for a planet, the parent planet's id for a moon
}

export interface InventoryItemDto {
  kind: 'resource' | 'part'
  name: string
  qty: number
}

export interface SystemState {
  systemId: number
  systemName: string
  planets: PlanetDto[] // insertion order = display order (a moon follows its parent row)
  inventory: InventoryItemDto[]
  turn: number
}

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

async function readSystemState(db: GameDb): Promise<SystemState> {
  const [save] = await db.db.select().from(schema.saves).limit(1)
  const systems = await db.db.select().from(schema.solarSystems)
  const current = systems.find((s) => s.isCurrent)!
  const planets = (await db.db.select().from(schema.planets).where(eq(schema.planets.systemId, current.id))).map((p) => ({
    id: p.id,
    name: p.name,
    type: p.type,
    hazard: p.hazard,
    explored: p.explored,
    parent: p.parentId,
  }))
  const inventory = (await db.db.select().from(schema.inventoryItems)).map((i) => ({ kind: i.kind as 'resource' | 'part', name: i.name, qty: i.qty }))
  return { systemId: current.id, systemName: current.name, planets, inventory, turn: save.turn }
}

export async function getSystemState(db: GameDb): Promise<SystemState> {
  await ensureSave(db)
  return readSystemState(db)
}

// --- Crew roster --------------------------------------------------------------

export interface CrewDto {
  id: number
  name: string
  role: string
  traitGood: string
  traitBad: string
  origin: string // 'STARTING CREW' or '<planet>, <system>' for members found while exploring
}

// The full roster in join order (starting crew first, then finds). Auto-initializes like the other reads.
export async function getCrewState(db: GameDb): Promise<CrewDto[]> {
  await ensureSave(db)
  return (await db.db.select().from(schema.crew)).map((c) => ({ id: c.id, name: c.name, role: c.role, traitGood: c.traitGood, traitBad: c.traitBad, origin: c.origin }))
}

export interface ExploreResult extends SystemState {
  outcome: FoundItem[] // what this scan found (may be empty — some scans find nothing)
  crewFound: CrewDto | null // a member who joined the ship on this scan (null when none)
}

// Scan one body of the save: deterministic haul from (seed, planet id), marks it explored,
// costs a turn, accumulates finds into inventory and writes an event. The same per-planet
// rng stream also rolls for a crew member (~18% of scans) who joins the roster. Any existing
// planet may be scanned (the UI only offers the current system's rows).
export async function explorePlanet(db: GameDb, planetId: number): Promise<ExploreResult> {
  await ensureSave(db)
  const [save] = await db.db.select().from(schema.saves).limit(1)
  const planets = await db.db.select().from(schema.planets)
  const target = planets.find((p) => p.id === planetId)
  if (!target) throw new ExploreError(404, `Unknown planet ${planetId}`)
  if (target.explored) throw new ExploreError(409, `${target.name} was already explored`)

  const rng = explorationRng(save.seed, target.id)
  const outcome = rollExploration(rng) // resource/part haul first…
  const takenNames = new Set((await db.db.select().from(schema.crew)).map((c) => c.name))
  const foundMember = rollCrewMember(rng, takenNames) // …then the crew roll on the same stream
  const turn = save.turn + 1

  await db.db.update(schema.planets).set({ explored: true }).where(eq(schema.planets.id, target.id))
  for (const item of outcome) {
    // Accumulate: the same kind+name on this save bumps qty instead of adding a row.
    const existing = (await db.db.select().from(schema.inventoryItems)).find((i) => i.kind === item.kind && i.name === item.name)
    if (existing) {
      await db.db.update(schema.inventoryItems).set({ qty: existing.qty + item.qty }).where(eq(schema.inventoryItems.id, existing.id))
    } else {
      await db.db.insert(schema.inventoryItems).values({ saveId: save.id, kind: item.kind, name: item.name, qty: item.qty })
    }
  }

  let crewFound: CrewDto | null = null
  if (foundMember) {
    const systems = await db.db.select().from(schema.solarSystems)
    const systemName = systems.find((s) => s.id === target.systemId)?.name ?? 'unknown system'
    const [row] = await db.db.insert(schema.crew).values({ saveId: save.id, name: foundMember.name, role: foundMember.role, traitGood: foundMember.traitGood, traitBad: foundMember.traitBad, origin: `${target.name}, ${systemName}` }).returning()
    crewFound = { id: row.id, name: row.name, role: row.role, traitGood: row.traitGood, traitBad: row.traitBad, origin: row.origin }
  }

  const foundText = outcome.length > 0 ? outcome.map((i) => `${i.qty}× ${i.name}`).join(', ') : 'nothing'
  const crewText = crewFound ? ` — ${crewFound.name} joined the crew` : ''
  await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
  await db.db.insert(schema.events).values({ saveId: save.id, turn, type: 'explore', message: `Explored ${target.name} — found ${foundText}${crewText}`, createdAt: new Date().toISOString() })
  await checkMissionCompletion(db, save.id, turn, { outcome }) // an ACTIVE EXPLORE/FIND may have advanced or completed
  await topUpMissionBoard(db)
  await persist(db)

  return { ...(await readSystemState(db)), outcome, crewFound }
}