package main

import (
	"crypto/rand"
	"crypto/sha256"
	"database/sql"
	"encoding/hex"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"golang.org/x/crypto/bcrypt"
	_ "modernc.org/sqlite"
)

type User struct {
	Username string `json:"username"`
	ID uint64 `json:"id"`
	Password string `json:"password"`
}

type File struct {
	Name string `json:"name"`
	Path string `json:"path"`
	ParentId uint64 `json:"parent_id"`
	IsDirectory bool `json:"is_directory"`
	
	Size uint64 `json:"size"`
	MimeType string `json:"mime_type"`
	Hash string `json:"hash"`

	OwnerId uint64 `json:"owner_id"`

	UploadToken string `json:"token"`
}

func getUserFromToken(db *sql.DB, token string) (uint64, error) {
	var userID uint64
	var expiresAt time.Time

	query := `SELECT user_id, expires_at FROM tokens WHERE token = ?`
	err := db.QueryRow(query, token).Scan(&userID, &expiresAt)

	if err == sql.ErrNoRows {
		return 0, fmt.Errorf("invalid token")
	}
	if err != nil {
		return 0, err
	}

	if time.Now().After(expiresAt) {
		return 0, fmt.Errorf("token expired")
	}

	return userID, nil
}

func main() {

	storagePath := flag.String("storage-path", "/opt/chsp_files", "Path where user uploaded files are stored.")
	dbPath := flag.String("db-path", "/opt/chsp_files/files.db", "Path to the SQLite database which stores file information")
	port := flag.Int("port", 5001, "Port to run the server on")

	flag.Parse()

	log.SetPrefix("chookspace/files ")

	// Set up database
	db, err := sql.Open("sqlite", *dbPath)

	if err != nil {
		log.Fatal(err)
	}

	if err := db.Ping(); err != nil {
		log.Fatal(err)
	}

	{
		// Create tables
		query := `
			CREATE TABLE IF NOT EXISTS users(
				id INTEGER PRIMARY KEY AUTOINCREMENT,
				username TEXT UNIQUE NOT NULL,
				password TEXT NOT NULL
			);

			CREATE TABLE IF NOT EXISTS tokens(
				id INTEGER PRIMARY KEY AUTOINCREMENT,
				user_id INTEGER NOT NULL,
				token TEXT UNIQUE NOT NULL,
				created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
				expires_at DATETIME NOT NULL,

				FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
			);

			CREATE TABLE IF NOT EXISTS files(
				id INTEGER PRIMARY KEY AUTOINCREMENT,
				name TEXT NOT NULL,
				path TEXT UNIQUE NOT NULL,
				parent_id INTEGER,
				is_directory BOOLEAN NOT NULL DEFAULT 0,
				
				size INTEGER DEFAULT 0,
				mime_type TEXT,
				hash TEXT,
				
				storage_path TEXT,
				
				owner_id INTEGER NOT NULL,
				
				created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
				updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
				
				FOREIGN KEY (owner_id) REFERENCES users(id) ON DELETE CASCADE,
				FOREIGN KEY (parent_id) REFERENCES files(id) ON DELETE CASCADE
			);
		`
		if _, err := db.Exec(query); err != nil {
			log.Fatal(err)
		}
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprint(w, "dingus")
		log.Print("we recieved a get to the root")
	})

	// Handle user creation
	http.HandleFunc("/api/create_user", func(w http.ResponseWriter, r *http.Request) {
		var user User
		w.Header().Set("Content-Type", "application/json")

		// Decode JSON
		if err := json.NewDecoder(r.Body).Decode(&user); err != nil {
			w.WriteHeader(http.StatusBadRequest)
			fmt.Fprintf(w, `{
				"status": "error",
				"why": "%s"
			}`, err.Error())
			return
		}

		// Hash password
		hash, hasherr := bcrypt.GenerateFromPassword([]byte(user.Password), bcrypt.DefaultCost)
		if hasherr != nil {
			w.WriteHeader(http.StatusInternalServerError)
			fmt.Fprintf(w, `{
				"status": "error",
				"why": "%s"
			}`, hasherr.Error())
			return
		}

		// Do SQL stuff
		_, dberr := db.Exec(`INSERT INTO users (username, password) VALUES (?, ?)`, user.Username, string(hash))
		if dberr != nil {
			w.WriteHeader(http.StatusBadRequest)
			fmt.Fprintf(w, `{
				"status": "error",
				"why": "%s"
			}`, dberr.Error())
			return
		}

		// Yay everything worked it seems
		fmt.Fprintf(w, `{
			"status": "success"
		}`)
	})

	// Handle getting files
	http.HandleFunc("/api/get_file", func(w http.ResponseWriter, r *http.Request) {
		// Parse JSON
		var file File
		if err := json.NewDecoder(r.Body).Decode(&file); err != nil {
			w.WriteHeader(http.StatusBadRequest)
			fmt.Fprintf(w, `{
				"status": "error",
				"description": "bad JSON",
				"why": "%s"
			}`, err.Error())
			return
		}

		// Authenticate user
		uid, err := getUserFromToken(db, file.UploadToken)
		if err != nil {
			w.WriteHeader(http.StatusUnauthorized)
			fmt.Fprintf(w, `{
				"status": "error",
				"description", "%s"
			}`, err.Error())
			return
		}
		file.OwnerId = uid

		// Find file
		fileQuery := `SELECT storage_path, mime_type, size, name FROM files WHERE owner_id = ? AND path = ?`
		if err := db.QueryRow(fileQuery, file.OwnerId, file.Path).Scan(&file.Path, &file.MimeType, &file.Size, &file.Name); err != nil {
			if err == sql.ErrNoRows {
				w.WriteHeader(http.StatusNotFound)
				fmt.Fprintf(w, `{
					"status": "error",
					"description": "file not found",
					"why": "%s"
				}`, err.Error())
				return
			}
			w.WriteHeader(http.StatusInternalServerError)
			fmt.Fprintf(w, `{
				"status": "error",
				"description": "internal server error",
				"why": "%s"
			}`, err.Error())
			return
		}

		// Get the file
		storageFile, err := os.Open(file.Path)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError) 
			fmt.Fprintf(w, `{
				"status": "error",
				"why": "%s"
			}`, err.Error())
			return
		}
		defer storageFile.Close()

		// Set headers
		w.Header().Set("Content-Type", file.MimeType)
		w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, file.Name))
		w.Header().Set("Content-Length", fmt.Sprintf("%d", file.Size))
		if _, err := io.Copy(w, storageFile); err != nil {
			log.Printf("Error while sending file: %s", err)
			return
		}
	})

	// Handle files sent to the server (special since JSON and files don't mix)
	http.HandleFunc("/api/send_file", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		
		// Parse multipart form (32MB max memory)
		if err := r.ParseMultipartForm(32 << 20); err != nil {
			w.WriteHeader(http.StatusBadRequest)
			json.NewEncoder(w).Encode(map[string]string{
				"status": "error",
				"why": err.Error(),
			})
			return
		}
		
		// Get auth credentials from form fields
		token := r.FormValue("token")
		
		// Authenticate user
		uid, err := getUserFromToken(db, token)
		if err != nil {
			w.WriteHeader(http.StatusUnauthorized)
			fmt.Fprintf(w, `{
				"status": "error",
				"description", "%s"
			}`, err.Error())
			return
		}
		userID := uid

		// Get the uploaded file
		file, header, err := r.FormFile("file")
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			json.NewEncoder(w).Encode(map[string]string{
				"status": "error",
				"why": "no file provided",
			})
			return
		}
		defer file.Close()
		
		// Read file contents and compute hash
		fileBytes, err := io.ReadAll(file)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			json.NewEncoder(w).Encode(map[string]string{
				"status": "error",
				"why": "failed to read file",
			})
			return
		}
		
		// Compute SHA256 hash
		hasher := sha256.New()
		hasher.Write(fileBytes)
		fileHash := hex.EncodeToString(hasher.Sum(nil))
		
		// Create storage directory structure (first 2 chars of hash)
		storageDir := filepath.Join(*storagePath, fileHash[:2], fileHash[2:4])
		if err := os.MkdirAll(storageDir, 0755); err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			json.NewEncoder(w).Encode(map[string]string{
				"status": "error",
				"why": "failed to create storage directory",
			})
			return
		}
		
		// Storage path: storage/ab/cd/abcdef123456...
		storagePath := filepath.Join(storageDir, fileHash)
		
		// Write file to disk (only if it doesn't already exist - deduplication!)
		if _, err := os.Stat(storagePath); os.IsNotExist(err) {
			if err := os.WriteFile(storagePath, fileBytes, 0644); err != nil {
				w.WriteHeader(http.StatusInternalServerError)
				json.NewEncoder(w).Encode(map[string]string{
					"status": "error",
					"why": "failed to save file",
				})
				return
			}
		}
		
		// Get file path from form (or default to root)
		filePath := r.FormValue("path")
		if filePath == "" {
			filePath = "/" + header.Filename
		}
		
		// Detect MIME type
		mimeType := http.DetectContentType(fileBytes)
		
		// Insert into database
		insertQuery := `
			INSERT INTO files (name, path, is_directory, size, mime_type, hash, storage_path, owner_id)
			VALUES (?, ?, 0, ?, ?, ?, ?, ?)
		`
		_, err = db.Exec(insertQuery, 
			header.Filename,
			filePath,
			len(fileBytes),
			mimeType,
			fileHash,
			storagePath,
			userID,
		)
		
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			json.NewEncoder(w).Encode(map[string]string{
				"status": "error",
				"why": "failed to save metadata",
			})
			return
		}
		
		json.NewEncoder(w).Encode(map[string]any{
			"status": "success",
			"hash": fileHash,
			"size": len(fileBytes),
		})
	})


	http.HandleFunc("/api/create_session", func(w http.ResponseWriter, r *http.Request) {
		var user User
		w.Header().Set("Content-Type", "application/json")

		// Decode JSON
		if err := json.NewDecoder(r.Body).Decode(&user); err != nil {
			w.WriteHeader(http.StatusBadRequest)
			fmt.Fprintf(w, `{
				"status": "error",
				"description": "bad JSON",
				"why": "%s"
			}`, err.Error())
			return
		}

		// Authenticate user
		var hashedPassword string
		authQuery := `SELECT id, password FROM users WHERE username = ?`
		if err := db.QueryRow(authQuery, user.Username).Scan(&user.ID, &hashedPassword); err != nil {
			w.WriteHeader(http.StatusUnauthorized)
			fmt.Fprintf(w, `{
				"status": "error",
				"description": "user not found",
				"why": "%s"
			}`, err.Error())
			return
		}

		if err := bcrypt.CompareHashAndPassword([]byte(hashedPassword), []byte(user.Password)); err != nil {
			w.WriteHeader(http.StatusUnauthorized)
			fmt.Fprintf(w, `{
				"status": "error",
				"description": "incorrect password",
				"why": "%s"
			}`, err.Error())
			return
		}

		tokenBytes := make([]byte, 64)
		rand.Read(tokenBytes)
		token := hex.EncodeToString(tokenBytes)
		expiresAt := time.Now().Add(30 * 24 * time.Hour)

		_, err := db.Exec(`INSERT INTO tokens (user_id, token, expires_at) VALUES (?, ?, ?)`, user.ID, token, expiresAt)

		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			fmt.Fprintf(w, `{
				"status": "error",
				"description": "internal server error",
				"why": "%s"
			}`, err.Error())
			return
		}

		fmt.Fprintf(w, `{
			"status": "success",
			"token": "%s"
		}`, token)
	})

	http.ListenAndServe(strings.Join([]string{":", strconv.Itoa(*port)}, ""), nil)
}