package app

import (
	"fmt"
	"net/http"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"go.etcd.io/bbolt"
)

const (
	AUTH_ADMIN   = "admin"
	AUTH_MAP     = "map"
	AUTH_MARKERS = "markers"
	AUTH_UPLOAD  = "upload"

	CharCleanupInterval = 10 * time.Second
	CharStaleThreshold  = 10 * time.Second
	TileUpdateInterval  = 30 * time.Minute
	MaxZoomLevel        = 5
	GridSize            = 100
	SessionMaxAge       = 7 * 24 * 3600 // 1 week in seconds
	MultipartMaxMemory  = 100 << 20     // 100 MB
	MergeMaxMemory      = 500 << 20     // 500 MB
	ClientVersion       = "4"
	SSETickInterval     = 5 * time.Second
	SSETileChannelSize  = 1000
	SSEMergeChannelSize = 5
)

// App is the main application (map server) state.
type App struct {
	gridStorage  string
	frontendRoot string
	db           *bbolt.DB

	characters map[string]Character
	chmu       sync.RWMutex

	gridUpdates  Topic[TileData]
	mergeUpdates Topic[Merge]
}

// NewApp creates an App with the given storage paths and database.
func NewApp(gridStorage, frontendRoot string, db *bbolt.DB) (*App, error) {
	return &App{
		gridStorage:  gridStorage,
		frontendRoot: frontendRoot,
		db:           db,
		characters:   make(map[string]Character),
	}, nil
}

// GridStorage returns the path to the grid storage directory.
func (a *App) GridStorage() string { return a.gridStorage }

// GridUpdates returns the tile update pub/sub topic.
func (a *App) GridUpdates() *Topic[TileData] { return &a.gridUpdates }

// MergeUpdates returns the merge event pub/sub topic.
func (a *App) MergeUpdates() *Topic[Merge] { return &a.mergeUpdates }

// DB returns the underlying bbolt database.
func (a *App) DB() *bbolt.DB { return a.db }

// GetCharacters returns a copy of all characters.
func (a *App) GetCharacters() []Character {
	a.chmu.RLock()
	defer a.chmu.RUnlock()
	chars := make([]Character, 0, len(a.characters))
	for _, v := range a.characters {
		chars = append(chars, v)
	}
	return chars
}

// WithCharacters provides locked mutable access to the character map.
func (a *App) WithCharacters(fn func(chars map[string]Character)) {
	a.chmu.Lock()
	defer a.chmu.Unlock()
	fn(a.characters)
}

// CleanChars runs a background loop that removes stale character entries.
func (a *App) CleanChars() {
	for range time.Tick(CharCleanupInterval) {
		a.chmu.Lock()
		for n, c := range a.characters {
			if c.Updated.Before(time.Now().Add(-CharStaleThreshold)) {
				delete(a.characters, n)
			}
		}
		a.chmu.Unlock()
	}
}

// serveSPARoot serves the map SPA: static files from frontend, fallback to index.html.
func (a *App) ServeSPARoot(rw http.ResponseWriter, req *http.Request) {
	path := req.URL.Path

	if path == "/map" || path == "/map/" {
		http.Redirect(rw, req, "/", http.StatusFound)
		return
	}
	if strings.HasPrefix(path, "/map/") {
		rest := path[len("/map/"):]
		switch {
		case rest == "login":
			http.Redirect(rw, req, "/login", http.StatusFound)
			return
		case rest == "profile":
			http.Redirect(rw, req, "/profile", http.StatusFound)
			return
		case rest == "admin" || strings.HasPrefix(rest, "admin/"):
			http.Redirect(rw, req, "/"+rest, http.StatusFound)
			return
		case rest == "setup":
			http.Redirect(rw, req, "/setup", http.StatusFound)
			return
		case strings.HasPrefix(rest, "character/"):
			http.Redirect(rw, req, "/"+rest, http.StatusFound)
			return
		case strings.HasPrefix(rest, "grid/"):
			http.Redirect(rw, req, "/"+rest, http.StatusFound)
			return
		}
	}

	filePath := strings.TrimPrefix(path, "/")
	if filePath == "" {
		filePath = "index.html"
	}
	filePath = filepath.Clean(filePath)
	if filePath == "." || filePath == ".." || strings.HasPrefix(filePath, "..") {
		http.NotFound(rw, req)
		return
	}
	tryPaths := []string{filePath, filepath.Join("map", filePath)}
	var f http.File
	for _, p := range tryPaths {
		var err error
		f, err = http.Dir(a.frontendRoot).Open(p)
		if err == nil {
			break
		}
	}
	if f == nil {
		http.ServeFile(rw, req, filepath.Join(a.frontendRoot, "index.html"))
		return
	}
	defer f.Close()
	stat, err := f.Stat()
	if err != nil || stat.IsDir() {
		http.ServeFile(rw, req, filepath.Join(a.frontendRoot, "index.html"))
		return
	}
	http.ServeContent(rw, req, stat.Name(), stat.ModTime(), f)
}

// --- Domain types ---

// Session represents an authenticated user session.
type Session struct {
	ID        string
	Username  string
	Auths     Auths `json:"-"`
	TempAdmin bool
}

// ClientUsernameKey is the context key for the username that owns a client token (set by client handlers).
var ClientUsernameKey = &struct{ key string }{key: "clientUsername"}

// Character represents a game character on the map.
type Character struct {
	Name     string   `json:"name"`
	ID       int      `json:"id"`
	Map      int      `json:"map"`
	Position Position `json:"position"`
	Type     string   `json:"type"`
	Updated  time.Time
	Username string `json:"-"` // owner of the token that last updated this character; not sent to API
}

// Marker represents a map marker stored per grid.
type Marker struct {
	Name     string   `json:"name"`
	ID       int      `json:"id"`
	GridID   string   `json:"gridID"`
	Position Position `json:"position"`
	Image    string   `json:"image"`
	Hidden   bool     `json:"hidden"`
}

// FrontendMarker is a marker with map-level coordinates for the frontend.
type FrontendMarker struct {
	Name     string   `json:"name"`
	ID       int      `json:"id"`
	Map      int      `json:"map"`
	Position Position `json:"position"`
	Image    string   `json:"image"`
	Hidden   bool     `json:"hidden"`
}

// MapInfo describes a map instance.
type MapInfo struct {
	ID       int
	Name     string
	Hidden   bool
	Priority bool
}

// GridData represents a grid tile with its coordinates and map assignment.
type GridData struct {
	ID         string
	Coord      Coord
	NextUpdate time.Time
	Map        int
}

// Coord represents a grid coordinate pair.
type Coord struct {
	X int `json:"x"`
	Y int `json:"y"`
}

// Position represents a pixel position within a grid.
type Position struct {
	X int `json:"x"`
	Y int `json:"y"`
}

// Name returns the string representation "X_Y" used as bucket keys.
func (c Coord) Name() string {
	return fmt.Sprintf("%d_%d", c.X, c.Y)
}

// Parent returns the parent coordinate at the next zoom level.
func (c Coord) Parent() Coord {
	if c.X < 0 {
		c.X--
	}
	if c.Y < 0 {
		c.Y--
	}
	return Coord{
		X: c.X / 2,
		Y: c.Y / 2,
	}
}

// Auths is a list of permission strings (e.g. "admin", "map", "upload").
type Auths []string

// Has returns true if the list contains the given permission.
func (a Auths) Has(auth string) bool {
	for _, v := range a {
		if v == auth {
			return true
		}
	}
	return false
}

// User represents a stored user account.
type User struct {
	Pass       []byte
	Auths      Auths
	Tokens     []string
	OAuthLinks map[string]string `json:"oauth_links,omitempty"`
	Email      string            `json:"email,omitempty"`
}

// Page holds page metadata for rendering.
type Page struct {
	Title string `json:"title"`
}

// Config holds the application config sent to the frontend.
type Config struct {
	Title string   `json:"title"`
	Auths []string `json:"auths"`
}

// TileData represents a tile image entry in the database.
type TileData struct {
	MapID int
	Coord Coord
	Zoom  int
	File  string
	Cache int64
}