package adventure

import (
	"fmt"
	"slices"
	"strings"
)

type gameState struct {
	currentRoom string
	inventory   []string
	rooms       map[string]*room
	items       map[string]*item
	flags       map[string]bool
	turns       int
}

type commandResult struct {
	output string
	exit   bool
}

func newGame() *gameState {
	rooms, items := newWorld()
	return &gameState{
		currentRoom: "oubliette",
		rooms:       rooms,
		items:       items,
		flags:       make(map[string]bool),
	}
}

func (g *gameState) dispatch(input string) commandResult {
	cmd := parseCommand(input)
	if cmd.verb == "" {
		return commandResult{}
	}

	g.turns++

	switch cmd.verb {
	case "look":
		return g.cmdLook(cmd.object)
	case "go":
		return g.cmdGo(cmd.object)
	case "take":
		return g.cmdTake(cmd.object)
	case "drop":
		return g.cmdDrop(cmd.object)
	case "use":
		return g.cmdUse(cmd.object)
	case "inventory":
		return g.cmdInventory()
	case "help":
		return g.cmdHelp()
	case "quit":
		return commandResult{output: "The darkness closes in. Session terminated.", exit: true}
	default:
		return commandResult{output: fmt.Sprintf("I don't understand '%s'. Type 'help' for available commands.", input)}
	}
}

func (g *gameState) cmdHelp() commandResult {
	help := `Available commands:
  look / examine [item]  - Look around or examine something
  go <direction>         - Move (north, south, east, west, up, down)
  take <item>            - Pick up an item
  drop <item>            - Drop an item
  use <item>             - Use an item
  inventory              - Check what you're carrying
  help                   - Show this help
  quit / exit            - End session

You can also just type a direction (n, s, e, w, u, d) to move.`
	return commandResult{output: help}
}

func (g *gameState) cmdLook(object string) commandResult {
	r := g.rooms[g.currentRoom]

	// Look at a specific item.
	if object != "" {
		return g.examineItem(object)
	}

	// Look at the room.
	return commandResult{output: g.describeRoom(r)}
}

func (g *gameState) describeRoom(r *room) string {
	var b strings.Builder

	fmt.Fprintf(&b, "== %s ==\n", r.name)

	// Dark room check.
	if r.darkDesc != "" && !g.hasItem("flashlight") {
		b.WriteString(r.darkDesc)
		return b.String()
	}

	b.WriteString(r.description)

	// List visible items.
	visibleItems := g.roomItems(r)
	if len(visibleItems) > 0 {
		b.WriteString("\n\nYou can see: ")
		names := make([]string, len(visibleItems))
		for i, id := range visibleItems {
			names[i] = g.items[id].name
		}
		b.WriteString(strings.Join(names, ", "))
	}

	// List exits.
	if len(r.exits) > 0 {
		b.WriteString("\n\nExits: ")
		dirs := make([]string, 0, len(r.exits))
		for dir := range r.exits {
			dirs = append(dirs, dir)
		}
		b.WriteString(strings.Join(dirs, ", "))
	}

	return b.String()
}

func (g *gameState) roomItems(r *room) []string {
	// In dark rooms without flashlight, can't see items.
	if r.darkDesc != "" && !g.hasItem("flashlight") {
		return nil
	}
	return r.items
}

func (g *gameState) examineItem(name string) commandResult {
	id := g.resolveItem(name)
	if id == "" {
		return commandResult{output: fmt.Sprintf("You don't see '%s' here.", name)}
	}
	return commandResult{output: g.items[id].description}
}

func (g *gameState) cmdGo(direction string) commandResult {
	if direction == "" {
		return commandResult{output: "Go where? Try a direction: north, south, east, west, up, down."}
	}

	r := g.rooms[g.currentRoom]
	destID, ok := r.exits[direction]
	if !ok {
		return commandResult{output: fmt.Sprintf("You can't go %s from here.", direction)}
	}

	// Check locked doors.
	if r.locked != nil {
		if flag, locked := r.locked[direction]; locked && !g.flags[flag] {
			return g.lockedMessage(direction)
		}
	}

	g.currentRoom = destID
	dest := g.rooms[destID]

	// Entering the exit room ends the game.
	if destID == "exit" {
		return commandResult{output: g.describeRoom(dest), exit: true}
	}

	return commandResult{output: g.describeRoom(dest)}
}

func (g *gameState) lockedMessage(direction string) commandResult {
	if direction == "east" && g.currentRoom == "archive" {
		return commandResult{output: "The steel door won't budge. The keycard reader blinks red, waiting."}
	}
	return commandResult{output: "The way is locked."}
}

func (g *gameState) cmdTake(name string) commandResult {
	if name == "" {
		return commandResult{output: "Take what?"}
	}

	r := g.rooms[g.currentRoom]

	// Can't take items in dark rooms.
	if r.darkDesc != "" && !g.hasItem("flashlight") {
		return commandResult{output: "It's too dark to find anything."}
	}

	id := g.resolveRoomItem(name)
	if id == "" {
		return commandResult{output: fmt.Sprintf("You don't see '%s' here.", name)}
	}

	it := g.items[id]
	if !it.takeable {
		return commandResult{output: fmt.Sprintf("You can't take the %s.", it.name)}
	}

	// Remove from room, add to inventory.
	g.removeRoomItem(r, id)
	g.inventory = append(g.inventory, id)
	return commandResult{output: fmt.Sprintf("Taken: %s", it.name)}
}

func (g *gameState) cmdDrop(name string) commandResult {
	if name == "" {
		return commandResult{output: "Drop what?"}
	}

	id := g.resolveInventoryItem(name)
	if id == "" {
		return commandResult{output: fmt.Sprintf("You're not carrying '%s'.", name)}
	}

	// Remove from inventory, add to room.
	g.removeInventoryItem(id)
	r := g.rooms[g.currentRoom]
	r.items = append(r.items, id)
	return commandResult{output: fmt.Sprintf("Dropped: %s", g.items[id].name)}
}

func (g *gameState) cmdUse(name string) commandResult {
	if name == "" {
		return commandResult{output: "Use what?"}
	}

	id := g.resolveInventoryItem(name)
	if id == "" {
		return commandResult{output: fmt.Sprintf("You're not carrying '%s'.", name)}
	}

	switch id {
	case "keycard":
		return g.useKeycard()
	case "rusty_key":
		return g.useRustyKey()
	case "flashlight":
		return commandResult{output: "The flashlight is already on. Its beam cuts through the darkness."}
	case "ethernet_cable":
		return commandResult{output: "You wave the cable around hopefully. Nothing happens. Both ends are chewed through anyway."}
	case "floppy_disk":
		return commandResult{output: "You don't have anything to put it in. Floppy drives went extinct decades ago."}
	case "note":
		return commandResult{output: g.items[id].description}
	default:
		return commandResult{output: fmt.Sprintf("You can't figure out how to use the %s here.", g.items[id].name)}
	}
}

func (g *gameState) useKeycard() commandResult {
	if g.currentRoom != "archive" {
		return commandResult{output: "There's nothing to use the keycard on here."}
	}
	if g.flags["archive_unlocked"] {
		return commandResult{output: "You already unlocked that door."}
	}
	g.flags["archive_unlocked"] = true
	return commandResult{output: "You swipe the keycard. The reader flashes green and the steel door clicks open with a heavy thunk."}
}

func (g *gameState) useRustyKey() commandResult {
	if g.currentRoom != "generator" {
		return commandResult{output: "There's nothing to use the rusty key on here."}
	}
	if g.flags["panel_opened"] {
		return commandResult{output: "The maintenance panel is already open."}
	}
	g.flags["panel_opened"] = true
	return commandResult{output: `The key fits. The maintenance panel swings open with a screech, revealing a logbook:

  MAINTENANCE LOG - GENERATOR B
  Last service: 2003-11-15
  Technician: J. Dunwich

  Notes: "Generator A offline permanently. B running on fumes.
  Fuel delivery canceled - 'facility decommissioned' per management.
  But the servers are still running. WHO IS USING THEM?
  Filed ticket #4,271. No response. As usual."

The entries stop after that date.`}
}

func (g *gameState) cmdInventory() commandResult {
	if len(g.inventory) == 0 {
		return commandResult{output: "You're not carrying anything."}
	}

	var b strings.Builder
	b.WriteString("You are carrying:\n")
	for _, id := range g.inventory {
		fmt.Fprintf(&b, "  - %s\n", g.items[id].name)
	}
	return commandResult{output: strings.TrimRight(b.String(), "\n")}
}

// hasItem checks if the player has an item in inventory.
func (g *gameState) hasItem(id string) bool {
	return slices.Contains(g.inventory, id)
}

// resolveItem finds an item by name in both room and inventory.
func (g *gameState) resolveItem(name string) string {
	if id := g.resolveInventoryItem(name); id != "" {
		return id
	}
	return g.resolveRoomItem(name)
}

// resolveRoomItem finds an item in the current room by partial name match.
func (g *gameState) resolveRoomItem(name string) string {
	r := g.rooms[g.currentRoom]
	name = strings.ToLower(name)
	for _, id := range r.items {
		if matchesItem(id, g.items[id].name, name) {
			return id
		}
	}
	return ""
}

// resolveInventoryItem finds an item in inventory by partial name match.
func (g *gameState) resolveInventoryItem(name string) string {
	name = strings.ToLower(name)
	for _, id := range g.inventory {
		if matchesItem(id, g.items[id].name, name) {
			return id
		}
	}
	return ""
}

// matchesItem checks if a search term matches an item's ID or display name.
func matchesItem(id, displayName, search string) bool {
	return id == search ||
		strings.ToLower(displayName) == search ||
		strings.Contains(id, search) ||
		strings.Contains(strings.ToLower(displayName), search)
}

func (g *gameState) removeRoomItem(r *room, id string) {
	for i, itemID := range r.items {
		if itemID == id {
			r.items = append(r.items[:i], r.items[i+1:]...)
			return
		}
	}
}

func (g *gameState) removeInventoryItem(id string) {
	for i, invID := range g.inventory {
		if invID == id {
			g.inventory = append(g.inventory[:i], g.inventory[i+1:]...)
			return
		}
	}
}