package main

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"time"

	_ "github.com/go-sql-driver/mysql"
)

// Config struct for database connection
type Config struct {
	Username string `json:"username"`
	Password string `json:"password"`
	Hostname string `json:"hostname"`
	Port     int    `json:"port"`
	Database string `json:"database"`
}

// QueryRequest from the frontend
type QueryRequest struct {
	ID    string `json:"id"`
	Query string `json:"query"`
}

// QueryResult represents a single historical query execution
type QueryResult struct {
	ID           string          `json:"id"`
	Query        string          `json:"query"`
	Timestamp    int64           `json:"timestamp"`
	Error        string          `json:"error,omitempty"`
	Columns      []string        `json:"columns,omitempty"`
	Rows         [][]interface{} `json:"rows,omitempty"`
	RowsAffected int64           `json:"rowsAffected,omitempty"`
}

var db *sql.DB
var historyDir = "./history"

func main() {
	// Load configuration
	file, err := os.Open("config.json")
	if err != nil {
		log.Fatalf("Failed to open config file: %v", err)
	}
	defer file.Close()

	var config Config
	decoder := json.NewDecoder(file)
	if err := decoder.Decode(&config); err != nil {
		log.Fatalf("Failed to decode config: %v", err)
	}

	// Connect to the database
	dsn := fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?parseTime=true",
		config.Username, config.Password, config.Hostname, config.Port, config.Database)
	db, err = sql.Open("mysql", dsn)
	if err != nil {
		log.Fatalf("Failed to open database connection: %v", err)
	}
	defer db.Close()

	if err := db.Ping(); err != nil {
		log.Fatalf("Failed to connect to the database: %v", err)
	}

	log.Println("Successfully connected to the database.")

	// Ensure history directory exists
	if _, err := os.Stat(historyDir); os.IsNotExist(err) {
		os.Mkdir(historyDir, 0755)
	}

	// HTTP Handlers
	http.HandleFunc("/", serveIndex)
	http.HandleFunc("/query", handleQuery)
	http.HandleFunc("/history", handleHistory)

	log.Println("Starting server on :8080...")
	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatalf("Server failed: %v", err)
	}
}

func serveIndex(w http.ResponseWriter, r *http.Request) {
	http.ServeFile(w, r, "index.html")
}

func handleHistory(w http.ResponseWriter, r *http.Request) {
	files, err := ioutil.ReadDir(historyDir)
	if err != nil {
		http.Error(w, "Could not read history", http.StatusInternalServerError)
		return
	}

	var history []QueryResult
	for _, file := range files {
		if filepath.Ext(file.Name()) == ".json" {
			data, err := ioutil.ReadFile(filepath.Join(historyDir, file.Name()))
			if err != nil {
				continue
			}
			var qr QueryResult
			if err := json.Unmarshal(data, &qr); err == nil {
				history = append(history, qr)
			}
		}
	}

	// Sort by timestamp, oldest first
	sort.Slice(history, func(i, j int) bool {
		return history[i].Timestamp < history[j].Timestamp
	})

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(history)
}

func handleQuery(w http.ResponseWriter, r *http.Request) {
	var req QueryRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	query := strings.TrimSpace(req.Query)
	isSelect := strings.HasPrefix(strings.ToLower(query), "select") || strings.HasPrefix(strings.ToLower(query), "show") || strings.HasPrefix(strings.ToLower(query), "describe")

	result := QueryResult{
		ID:        req.ID,
		Query:     req.Query,
		Timestamp: time.Now().UnixNano(),
	}

	// Generate new ID if it's a new query
	if result.ID == "" {
		result.ID = strconv.FormatInt(result.Timestamp, 10)
	}

	if isSelect {
		// It's a query that returns rows
		rows, err := db.Query(query)
		if err != nil {
			result.Error = err.Error()
		} else {
			defer rows.Close()
			cols, _ := rows.Columns()
			result.Columns = cols

			for rows.Next() {
				// Create a slice of interface{}'s to represent a row
				columns := make([]interface{}, len(cols))
				columnPointers := make([]interface{}, len(cols))
				for i := range columns {
					columnPointers[i] = &columns[i]
				}

				// Scan the result into the column pointers...
				if err := rows.Scan(columnPointers...); err != nil {
					result.Error = err.Error()
					break
				}

				// Convert byte slices to strings for better JSON representation
				for i, col := range columns {
					if b, ok := col.([]byte); ok {
						columns[i] = string(b)
					}
				}

				result.Rows = append(result.Rows, columns)
			}
			if err := rows.Err(); err != nil {
				result.Error = err.Error()
			}
		}
	} else {
		// It's a statement like INSERT, UPDATE, DELETE
		res, err := db.Exec(query)
		if err != nil {
			result.Error = err.Error()
		} else {
			affected, err := res.RowsAffected()
			if err != nil {
				result.Error = err.Error()
			} else {
				result.RowsAffected = affected
			}
		}
	}

	// Save to history
	filePath := filepath.Join(historyDir, result.ID+".json")
	fileData, _ := json.MarshalIndent(result, "", "  ")
	if err := ioutil.WriteFile(filePath, fileData, 0644); err != nil {
		log.Printf("Failed to write history file %s: %v", filePath, err)
		// Don't send a server error back to client, they can still see the result
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(result)
}