package game

import (
	"fmt"
	"iter"
	"math"
	"slices"

	"github.com/google/uuid"
	e "github.com/iliadenisov/galaxy/internal/error"
)

type Fleet struct {
	ID      uuid.UUID `json:"id"`
	OwnerID uuid.UUID `json:"ownerId"`
	Name    string    `json:"name"`
}

func FleetState(g *Game, fleetID uuid.UUID) (ShipGroupState, *uint, *InSpace) {
	fi := slices.IndexFunc(g.Fleets, func(f Fleet) bool { return f.ID == fleetID })
	if fi < 0 {
		panic("FleetState: fleet id not found: " + fleetID.String())
	}
	ri := slices.IndexFunc(g.Race, func(r Race) bool { return r.ID == g.Fleets[fi].OwnerID })
	if ri < 0 {
		panic("FleetState: race id not found: " + g.Fleets[fi].OwnerID.String())
	}
	var state *ShipGroupState
	var onPlanet *uint
	var is *InSpace
	for sg := range FleetGroups(g, ri, fi) {
		if state == nil {
			s := sg.State()
			state = &s
			if planet, ok := sg.OnPlanet(); ok {
				onPlanet = &planet
			}
			is = sg.StateInSpace
			continue
		}
		if *state != sg.State() {
			panic(fmt.Sprintf("FleetState: one or more ships in race's %q fleet %q has different states", g.Race[ri].Name, g.Fleets[fi].Name))
		}
		if planet, ok := sg.OnPlanet(); ok && onPlanet != nil && *onPlanet != planet {
			for sg := range FleetGroups(g, ri, fi) {
				fmt.Println("group", sg.Index, "fleet", sg.FleetID, g.Fleets[fi].Name, "state", sg.State(), "on", sg.Destination)
			}
			panic(fmt.Sprintf("FleetState: one or more ships in race's %q fleet %q are on different planets: %d <> %d", g.Race[ri].Name, g.Fleets[fi].Name, *onPlanet, planet))
		}
		if (is == nil && sg.StateInSpace != nil) || (is != nil && sg.StateInSpace == nil) {
			panic(fmt.Sprintf("FleetState: one or more ships in race's %q fleet %q on_planet and in_space at the same time", g.Race[ri].Name, g.Fleets[fi].Name))
		}
		if is != nil && sg.StateInSpace != nil && !is.Equal(*sg.StateInSpace) {
			panic(fmt.Sprintf("FleetState: one or more ships in race's %q fleet %q has different is_space states", g.Race[ri].Name, g.Fleets[fi].Name))
		}
	}
	if state == nil {
		panic(fmt.Sprintf("FleetState: race's %q fleet %q has no ships", g.Race[ri].Name, g.Fleets[fi].Name))
	}
	return *state, onPlanet, is
}

// TODO: Hello! Wanna know fleet's speed? Good. Implement & test this func first.
func (g Game) FleetSpeed(fl Fleet) float64 {
	result := math.MaxFloat64
	for sg := range g.ShipGroups {
		if g.ShipGroups[sg].FleetID == nil || *g.ShipGroups[sg].FleetID != fl.ID {
			continue
		}
		st := g.mustShipType(g.ShipGroups[sg].TypeID)
		typeSpeed := g.ShipGroups[sg].Speed(st)
		if typeSpeed < result {
			result = typeSpeed
		}
	}
	return result
}

func (g *Game) JoinShipGroupToFleet(raceName, fleetName string, group, count uint) error {
	ri, err := g.raceIndex(raceName)
	if err != nil {
		return err
	}
	return g.joinShipGroupToFleetInternal(ri, fleetName, group, count)
}

func (g *Game) JoinFleets(raceName, fleetSourceName, fleetTargetName string) error {
	ri, err := g.raceIndex(raceName)
	if err != nil {
		return err
	}
	return g.joinFleetsInternal(ri, fleetSourceName, fleetTargetName)
}

func (g *Game) joinShipGroupToFleetInternal(ri int, fleetName string, groupIndex, quantity uint) (err error) {
	name, ok := validateTypeName(fleetName)
	if !ok {
		return e.NewEntityTypeNameValidationError("%q", name)
	}
	sgi := -1
	var maxIndex uint
	for i, sg := range g.listIndexShipGroups(ri) {
		if sgi < 0 && sg.Index == groupIndex {
			sgi = i
		}
		if sg.Index > maxIndex {
			maxIndex = sg.Index
		}
	}
	if sgi < 0 {
		return e.NewEntityNotExistsError("group #%d", groupIndex)
	}

	if g.ShipGroups[sgi].State() != StateInOrbit {
		return e.NewShipsBusyError()
	}

	if g.ShipGroups[sgi].Number < quantity {
		return e.NewJoinFleetGroupNumberNotEnoughError("%d<%d", g.ShipGroups[sgi].Number, quantity)
	}

	fi := g.fleetIndex(ri, name)
	if fi < 0 {
		fi, err = g.createFleet(ri, name)
		if err != nil {
			return err
		}
	} else {
		state, onPlanet, _ := FleetState(g, g.Fleets[fi].ID)
		if state != StateInOrbit || *onPlanet != g.ShipGroups[sgi].Destination {
			return e.NewShipsNotOnSamePlanetError("fleet: %s", fleetName)
		}
	}

	// FIXME: if g.ShipGroups[sgi].FleetID != nil { // delete old fleet if empty, ALSO mind breaking group }
	if quantity > 0 && quantity < g.ShipGroups[sgi].Number {
		// nsgi, err := g.breakGroupSafe(ri, groupIndex, quantity)
		// if err != nil {
		// 	return err
		// }
		// sgi = nsgi
		newGroup := g.ShipGroups[sgi]
		newGroup.Number -= quantity
		g.ShipGroups[sgi].Number = quantity
		newGroup.Index = maxIndex + 1
		g.ShipGroups = append(g.ShipGroups, newGroup)
	}

	g.ShipGroups[sgi].FleetID = &g.Fleets[fi].ID
	return nil
}

func (g *Game) createFleet(ri int, name string) (int, error) {
	n, ok := validateTypeName(name)
	if !ok {
		return 0, e.NewEntityTypeNameValidationError("%q", n)
	}
	if fl := g.fleetIndex(ri, n); fl >= 0 {
		return 0, e.NewEntityTypeNameDuplicateError("fleet %w", g.Fleets[fl].Name)
	}
	fleets := slices.Clone(g.Fleets)
	fleets = append(fleets, Fleet{
		ID:      uuid.New(),
		OwnerID: g.Race[ri].ID,
		Name:    n,
	})
	g.Fleets = fleets
	return len(g.Fleets) - 1, nil
}

func (g *Game) joinFleetsInternal(ri int, fleetSourceName, fleetTargetName string) (err error) {
	fiSource := g.fleetIndex(ri, fleetSourceName)
	if fiSource < 0 {
		return e.NewEntityNotExistsError("source fleet %s", fleetSourceName)
	}
	fiTarget := g.fleetIndex(ri, fleetTargetName)
	if fiTarget < 0 {
		return e.NewEntityNotExistsError("target fleet %s", fleetTargetName)
	}
	srcState, planet1, _ := FleetState(g, g.Fleets[fiSource].ID)
	tgtState, planet2, _ := FleetState(g, g.Fleets[fiTarget].ID)
	if srcState != StateInOrbit || srcState != tgtState || *planet1 != *planet2 {
		return e.NewShipsNotOnSamePlanetError()
	}
	for sgi, sg := range g.listIndexShipGroups(ri) {
		if sg.FleetID != nil && *sg.FleetID == g.Fleets[fiSource].ID {
			g.ShipGroups[sgi].FleetID = &g.Fleets[fiTarget].ID
		}
	}
	return g.deleteFleetSafe(ri, fleetSourceName)
}

func (g *Game) deleteFleetSafe(ri int, name string) error {
	fi := g.fleetIndex(ri, name)
	if fi < 0 {
		return e.NewEntityNotExistsError("fleet %s", name)
	}
	for sgi := range g.ShipGroups {
		if g.ShipGroups[sgi].FleetID != nil && *g.ShipGroups[sgi].FleetID == g.Fleets[fi].ID {
			return e.NewEntityInUseError("fleet %s: race %s, group #%d", name, g.Race[ri].Name, g.ShipGroups[sgi].Number)
		}
	}
	g.Fleets = append(g.Fleets[:fi], g.Fleets[fi+1:]...)
	return nil
}

func (g Game) fleetIndex(ri int, name string) int {
	return slices.IndexFunc(g.Fleets, func(f Fleet) bool { return f.OwnerID == g.Race[ri].ID && f.Name == name })
}

func (g Game) listFleets(ri int) iter.Seq[Fleet] {
	return func(yield func(Fleet) bool) {
		for _, fl := range g.listIndexFleets(ri) {
			if !yield(fl) {
				return
			}
		}
	}
}

func (g Game) listIndexFleets(ri int) iter.Seq2[int, Fleet] {
	return func(yield func(int, Fleet) bool) {
		for i := range g.Fleets {
			if g.Fleets[i].OwnerID == g.Race[ri].ID {
				if !yield(i, g.Fleets[i]) {
					return
				}
			}
		}
	}
}

func FleetGroups(g *Game, ri, fi int) iter.Seq[ShipGroup] {
	if len(g.Fleets) < fi+1 {
		panic(fmt.Sprintf("FleetGroups: game fleets index %d invalid: len=%d", fi, len(g.Fleets)))
	}
	return func(yield func(ShipGroup) bool) {
		for sg := range g.listShipGroups(ri) {
			if sg.FleetID != nil && *sg.FleetID == g.Fleets[fi].ID {
				if !yield(sg) {
					break
				}
			}
		}
	}
}