package sim

import (
	"wh/config"
	"wh/fixed"
	"wh/world"
)

// tickCtx is per-tick shared context; asteroid positions are computed lazily
// and cached because several ships may query them in one tick.
type tickCtx struct {
	s     *State
	cfg   config.Config
	tick  int
	now   int64
	stPos fixed.Vec
	stVel fixed.Vec
	res   *DayResult
	sold  *[world.NumOre]int64

	astPos, astVel []fixed.Vec
	astDone        []bool
}

func newTickCtx(s *State, cfg config.Config, tick int, now int64, stPos, stVel fixed.Vec, res *DayResult, sold *[world.NumOre]int64) *tickCtx {
	n := len(s.Asteroids)
	return &tickCtx{s: s, cfg: cfg, tick: tick, now: now, stPos: stPos, stVel: stVel, res: res, sold: sold,
		astPos: make([]fixed.Vec, n), astVel: make([]fixed.Vec, n), astDone: make([]bool, n)}
}

func (tc *tickCtx) asteroid(i int) (fixed.Vec, fixed.Vec) {
	if !tc.astDone[i] {
		tc.astPos[i], tc.astVel[i] = tc.s.Asteroids[i].Orbit.State(tc.now)
		tc.astDone[i] = true
	}
	return tc.astPos[i], tc.astVel[i]
}

// shipBus is one ship's view of its peripherals for one tick.
type shipBus struct {
	tc *tickCtx
	sh *Ship
}

func sat32(v int64) int32 {
	if v > 1<<31-1 {
		return 1<<31 - 1
	}
	if v < -1<<31 {
		return -1 << 31
	}
	return int32(v)
}

func kmInt(f fixed.F) int32 { return sat32(f.Floor()) }

// mps converts km/s to whole m/s.
func mps(f fixed.F) int32 { return sat32(f.MulInt(1000).Floor()) }

func (b *shipBus) target() (pos, vel fixed.Vec, ok bool) {
	id := b.sh.Target
	if id < 1 || id > int64(len(b.tc.s.Asteroids)) {
		return pos, vel, false
	}
	pos, vel = b.tc.asteroid(int(id - 1))
	return pos, vel, true
}

// axis returns component (port-base) of v (0=X, 1=Y, 2=Z) using conv, for
// ports laid out as three consecutive X, Y, Z registers.
func axis(v fixed.Vec, port, base uint16, conv func(fixed.F) int32) int32 {
	switch port - base {
	case 0:
		return conv(v.X)
	case 1:
		return conv(v.Y)
	}
	return conv(v.Z)
}

func (b *shipBus) In(port uint16) int32 {
	sh, tc := b.sh, b.tc
	switch {
	case port == PortTick:
		return int32(tc.tick)
	case port == PortDay:
		return sat32(tc.s.Day)
	case port == PortTicks:
		return int32(tc.cfg.TicksPerDay)
	case port >= PortPosX && port <= PortPosZ:
		return axis(sh.Pos, port, PortPosX, kmInt)
	case port >= PortVelX && port <= PortVelZ:
		return axis(sh.Vel, port, PortVelX, mps)
	case port == PortFuel:
		return sat32(sh.Fuel.Floor())
	case port == PortMass:
		return sat32(sh.Mass().Floor())
	case port == PortScanNearest:
		best, bestD := int64(0), fixed.Max
		for i := range tc.s.Asteroids {
			p, _ := tc.asteroid(i)
			if d := p.Sub(sh.Pos).Len(); d < bestD {
				best, bestD = int64(i+1), d
			}
		}
		return int32(best)
	case port >= PortScanRelX && port <= PortScanDist:
		p, v, ok := b.target()
		if !ok {
			return 0
		}
		rel, relV := p.Sub(sh.Pos), v.Sub(sh.Vel)
		switch {
		case port <= PortScanRelZ:
			return axis(rel, port, PortScanRelX, kmInt)
		case port <= PortScanRelVZ:
			return axis(relV, port, PortScanRelVX, mps)
		}
		return kmInt(rel.Len())
	case port >= PortScanOre && port < PortScanOre+8:
		if a := tc.s.asteroid(sh.Target); a != nil && port-PortScanOre < uint16(world.NumOre) {
			return sat32(a.Ore[port-PortScanOre])
		}
		return 0
	case port == PortCargo:
		return sat32(sh.CargoTotal())
	case port == PortCargoCap:
		return sat32(sh.Hull.CargoCap)
	case port >= PortCargoOre && port < PortCargoOre+8:
		if port-PortCargoOre < uint16(world.NumOre) {
			return sat32(sh.Cargo[port-PortCargoOre])
		}
		return 0
	case port >= PortStnRelX && port <= PortStnRelVZ:
		rel, relV := tc.stPos.Sub(sh.Pos), tc.stVel.Sub(sh.Vel)
		if port <= PortStnRelZ {
			return axis(rel, port, PortStnRelX, kmInt)
		}
		return axis(relV, port, PortStnRelVX, mps)
	case port == PortCredits:
		return sat32(sh.Earned)
	case port == PortUplinkNew:
		if sh.UplinkNew {
			return 1
		}
		return 0
	case port == PortUplinkLen:
		return sh.UplinkLen
	case port == PortMathAtan2:
		a := fixed.Atan2(fixed.FromInt(int64(sh.MathY)), fixed.FromInt(int64(sh.MathX)))
		return sat32(a.MulInt(1000).Floor())
	case port == PortMathHypot:
		return sat32(fixed.Hypot(fixed.FromInt(int64(sh.MathX)), fixed.FromInt(int64(sh.MathY))).Floor())
	case port == PortMathNorm3:
		return sat32(fixed.Norm3(fixed.FromInt(int64(sh.MathX)), fixed.FromInt(int64(sh.MathY)), fixed.FromInt(int64(sh.MathZ))).Floor())
	}
	return 0
}

func (b *shipBus) Out(port uint16, v int32) {
	sh, tc := b.sh, b.tc
	switch port {
	case PortThrottle:
		sh.Throttle = v
	case PortAzimuth:
		sh.Azimuth = v
	case PortPitch:
		sh.Pitch = v
	case PortScanSelect:
		sh.Target = int64(v)
	case PortMine:
		sh.Mining = v != 0
	case PortSell:
		if v == 0 || !tc.s.canReach(sh, tc.stPos, tc.stVel, DockRangeKm) {
			return
		}
		value := tc.s.Market.Value(sh.Cargo)
		if value == 0 {
			return
		}
		tc.s.Credits[sh.Owner] += value
		sh.Earned += value
		for o, kg := range sh.Cargo {
			tc.sold[o] += kg
			sh.Cargo[o] = 0
		}
		tc.res.Events = append(tc.res.Events, Event{tc.tick, sh.ID, "sold", itoa(value) + " credits"})
	case PortUplinkNew:
		sh.UplinkNew = false
	case PortMathX:
		sh.MathX = v
	case PortMathY:
		sh.MathY = v
	case PortMathZ:
		sh.MathZ = v
	}
}

func itoa(v int64) string {
	if v == 0 {
		return "0"
	}
	neg := v < 0
	if neg {
		v = -v
	}
	var b [20]byte
	i := len(b)
	for v > 0 {
		i--
		b[i] = byte('0' + v%10)
		v /= 10
	}
	if neg {
		i--
		b[i] = '-'
	}
	return string(b[i:])
}