registry/internal/database/memory.go

package database

import (
	"context"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/google/uuid"
	"github.com/modelcontextprotocol/registry/internal/model"
)

// MemoryDB is an in-memory implementation of the Database interface
type MemoryDB struct {
	entries map[string]*model.ServerDetail
	mu      sync.RWMutex
}

// NewMemoryDB creates a new instance of the in-memory database
func NewMemoryDB(e map[string]*model.Server) *MemoryDB {
	// Convert Server entries to ServerDetail entries
	serverDetails := make(map[string]*model.ServerDetail)
	for k, v := range e {
		serverDetails[k] = &model.ServerDetail{
			Server: *v,
		}
	}
	return &MemoryDB{
		entries: serverDetails,
	}
}

// compareSemanticVersions compares two semantic version strings
// Returns:
//
//	-1 if version1 < version2
//	 0 if version1 == version2
//	+1 if version1 > version2
func compareSemanticVersions(version1, version2 string) int {
	// Simple semantic version comparison
	// Assumes format: major.minor.patch

	parts1 := strings.Split(version1, ".")
	parts2 := strings.Split(version2, ".")

	// Pad with zeros if needed
	maxLen := len(parts1)
	if len(parts2) > maxLen {
		maxLen = len(parts2)
	}

	for len(parts1) < maxLen {
		parts1 = append(parts1, "0")
	}
	for len(parts2) < maxLen {
		parts2 = append(parts2, "0")
	}

	// Compare each part
	for i := 0; i < maxLen; i++ {
		num1, err1 := strconv.Atoi(parts1[i])
		num2, err2 := strconv.Atoi(parts2[i])

		// If parsing fails, fall back to string comparison
		if err1 != nil || err2 != nil {
			if parts1[i] < parts2[i] {
				return -1
			} else if parts1[i] > parts2[i] {
				return 1
			}
			continue
		}

		if num1 < num2 {
			return -1
		} else if num1 > num2 {
			return 1
		}
	}

	return 0
}

// List retrieves all MCPRegistry entries with optional filtering and pagination
//
//gocognit:ignore
func (db *MemoryDB) List(
	ctx context.Context,
	filter map[string]interface{},
	cursor string,
	limit int,
) ([]*model.Server, string, error) {
	if ctx.Err() != nil {
		return nil, "", ctx.Err()
	}

	if limit <= 0 {
		limit = 10 // Default limit
	}

	db.mu.RLock()
	defer db.mu.RUnlock()

	// Convert all entries to a slice for pagination
	var allEntries []*model.Server
	for _, entry := range db.entries {
		serverCopy := entry.Server
		allEntries = append(allEntries, &serverCopy)
	}

	// Simple filtering implementation
	var filteredEntries []*model.Server
	for _, entry := range allEntries {
		include := true

		// Apply filters if any
		for key, value := range filter {
			switch key {
			case "name":
				if entry.Name != value.(string) {
					include = false
				}
			case "repoUrl":
				if entry.Repository.URL != value.(string) {
					include = false
				}
			case "serverDetail.id":
				if entry.ID != value.(string) {
					include = false
				}
			case "version":
				if entry.VersionDetail.Version != value.(string) {
					include = false
				}
				// Add more filter options as needed
			}
		}

		if include {
			filteredEntries = append(filteredEntries, entry)
		}
	}

	// Find starting point for cursor-based pagination
	startIdx := 0
	if cursor != "" {
		for i, entry := range filteredEntries {
			if entry.ID == cursor {
				startIdx = i + 1 // Start after the cursor
				break
			}
		}
	}

	// Sort filteredEntries by ID for consistent pagination
	sort.Slice(filteredEntries, func(i, j int) bool {
		return filteredEntries[i].ID < filteredEntries[j].ID
	})

	// Apply pagination
	endIdx := startIdx + limit
	if endIdx > len(filteredEntries) {
		endIdx = len(filteredEntries)
	}

	var result []*model.Server
	if startIdx < len(filteredEntries) {
		result = filteredEntries[startIdx:endIdx]
	} else {
		result = []*model.Server{}
	}

	// Determine next cursor
	nextCursor := ""
	if endIdx < len(filteredEntries) {
		nextCursor = filteredEntries[endIdx-1].ID
	}

	return result, nextCursor, nil
}

// GetByID retrieves a single ServerDetail by its ID
func (db *MemoryDB) GetByID(ctx context.Context, id string) (*model.ServerDetail, error) {
	if ctx.Err() != nil {
		return nil, ctx.Err()
	}

	db.mu.RLock()
	defer db.mu.RUnlock()

	if entry, exists := db.entries[id]; exists {
		// Return a copy of the ServerDetail
		serverDetailCopy := *entry
		return &serverDetailCopy, nil
	}

	return nil, ErrNotFound
}

// Publish adds a new ServerDetail to the database
func (db *MemoryDB) Publish(ctx context.Context, serverDetail *model.ServerDetail) error {
	if ctx.Err() != nil {
		return ctx.Err()
	}

	db.mu.Lock()
	defer db.mu.Unlock()

	// check for name
	if serverDetail.Name == "" {
		return ErrInvalidInput
	}

	// check that the name and the version are unique
	// Also check version ordering - don't allow publishing older versions after newer ones
	var latestVersion string
	for _, entry := range db.entries {
		if entry.Name == serverDetail.Name {
			if entry.VersionDetail.Version == serverDetail.VersionDetail.Version {
				return ErrAlreadyExists
			}

			// Track the latest version for this package name
			if latestVersion == "" || compareSemanticVersions(entry.VersionDetail.Version, latestVersion) > 0 {
				latestVersion = entry.VersionDetail.Version
			}
		}
	}

	// If we found existing versions, check if the new version is older than the latest
	if latestVersion != "" && compareSemanticVersions(serverDetail.VersionDetail.Version, latestVersion) < 0 {
		return ErrInvalidVersion
	}

	if serverDetail.Repository.URL == "" {
		return ErrInvalidInput
	}

	// Generate a new ID for the server detail
	serverDetail.ID = uuid.New().String()
	serverDetail.VersionDetail.IsLatest = true // Assume the new version is the latest
	serverDetail.VersionDetail.ReleaseDate = time.Now().Format(time.RFC3339)
	// Store a copy of the entire ServerDetail
	serverDetailCopy := *serverDetail
	db.entries[serverDetail.ID] = &serverDetailCopy

	return nil
}

// Close closes the database connection
// For an in-memory database, this is a no-op
func (db *MemoryDB) Close() error {
	return nil
}

// Connection returns information about the database connection
func (db *MemoryDB) Connection() *ConnectionInfo {
	return &ConnectionInfo{
		Type:        ConnectionTypeMemory,
		IsConnected: true, // Memory DB is always connected
		Raw:         db.entries,
	}
}