package scheduler

import (
	"fmt"
	"sync"
)

// PluginQuotaConfig defines GPU limits for plugins.
type PluginQuotaConfig struct {
	Enabled         bool                   // Master switch for quota enforcement
	TotalGPUs       int                    // Global GPU limit across all plugins
	PerUserGPUs     int                    // Default per-user GPU limit
	PerUserServices int                    // Default per-user service count limit
	PerPluginLimits map[string]PluginLimit // Plugin-specific overrides
	UserOverrides   map[string]UserLimit   // Per-user overrides
}

// PluginLimit defines limits for a specific plugin.
type PluginLimit struct {
	MaxGPUs     int
	MaxServices int
}

// UserLimit defines per-user override limits.
type UserLimit struct {
	MaxGPUs        int
	MaxServices    int
	AllowedPlugins []string // Empty = all plugins allowed
}

// PluginUsage tracks GPU and service count for a user-plugin combination.
type PluginUsage struct {
	GPUs     int
	Services int
}

// PluginQuotaManager tracks active usage and enforces quotas.
type PluginQuotaManager struct {
	config      PluginQuotaConfig
	mu          sync.RWMutex
	usage       map[string]map[string]PluginUsage // userID -> pluginName -> usage
	pluginTotal map[string]int                    // pluginName -> total GPUs in use
	totalGPUs   int                               // global total GPUs in use
}

// NewPluginQuotaManager creates a new quota manager with the given configuration.
func NewPluginQuotaManager(config PluginQuotaConfig) *PluginQuotaManager {
	return &PluginQuotaManager{
		config:      config,
		usage:       make(map[string]map[string]PluginUsage),
		pluginTotal: make(map[string]int),
		totalGPUs:   0,
	}
}

// CheckQuota validates if a job can be submitted without exceeding limits.
// Returns nil if the job is allowed, or an error describing which limit would be exceeded.
func (m *PluginQuotaManager) CheckQuota(userID, pluginName string, gpuCount int) error {
	if !m.config.Enabled {
		return nil
	}

	if userID == "" {
		userID = "anonymous"
	}
	if pluginName == "" {
		pluginName = "default"
	}

	m.mu.RLock()
	defer m.mu.RUnlock()

	// Get user limits (with overrides)
	userLimit := m.getUserLimit(userID)

	// Check if user is allowed to use this plugin
	if len(userLimit.AllowedPlugins) > 0 {
		found := false
		for _, p := range userLimit.AllowedPlugins {
			if p == pluginName {
				found = true
				break
			}
		}
		if !found {
			return fmt.Errorf("user %s is not allowed to use plugin %s", userID, pluginName)
		}
	}

	// Check plugin-specific limits
	pluginLimit, hasPluginLimit := m.config.PerPluginLimits[pluginName]
	if hasPluginLimit {
		if pluginLimit.MaxGPUs > 0 && m.pluginTotal[pluginName]+gpuCount > pluginLimit.MaxGPUs {
			return fmt.Errorf("plugin %s GPU limit exceeded: %d requested, %d available of %d total",
				pluginName, gpuCount, pluginLimit.MaxGPUs-m.pluginTotal[pluginName], pluginLimit.MaxGPUs)
		}
		if pluginLimit.MaxServices > 0 {
			// Services limit is across all users for this plugin
			totalServices := 0
			for _, u := range m.usage {
				if p, ok := u[pluginName]; ok {
					totalServices += p.Services
				}
			}
			if totalServices+1 > pluginLimit.MaxServices {
				return fmt.Errorf("plugin %s service limit exceeded", pluginName)
			}
		}
	}

	// Check per-user limits
	effectiveUserGPUs := userLimit.MaxGPUs
	if effectiveUserGPUs == 0 {
		effectiveUserGPUs = m.config.PerUserGPUs
	}
	effectiveUserServices := userLimit.MaxServices
	if effectiveUserServices == 0 {
		effectiveUserServices = m.config.PerUserServices
	}

	// Calculate total user usage across all plugins
	totalUserGPUs := 0
	totalUserServices := 0
	for _, p := range m.usage[userID] {
		totalUserGPUs += p.GPUs
		totalUserServices += p.Services
	}

	if effectiveUserGPUs > 0 && totalUserGPUs+gpuCount > effectiveUserGPUs {
		return fmt.Errorf("user %s GPU limit exceeded: %d requested, %d available of %d total",
			userID, gpuCount, effectiveUserGPUs-totalUserGPUs, effectiveUserGPUs)
	}

	if effectiveUserServices > 0 && totalUserServices+1 > effectiveUserServices {
		return fmt.Errorf("user %s service limit exceeded: %d services of %d allowed",
			userID, totalUserServices+1, effectiveUserServices)
	}

	// Check global total GPU limit
	if m.config.TotalGPUs > 0 && m.totalGPUs+gpuCount > m.config.TotalGPUs {
		return fmt.Errorf("global GPU limit exceeded: %d requested, %d available of %d total",
			gpuCount, m.config.TotalGPUs-m.totalGPUs, m.config.TotalGPUs)
	}

	return nil
}

// RecordUsage increments usage counters when a job starts.
func (m *PluginQuotaManager) RecordUsage(userID, pluginName string, gpuCount int) {
	if !m.config.Enabled {
		return
	}

	if userID == "" {
		userID = "anonymous"
	}
	if pluginName == "" {
		pluginName = "default"
	}

	m.mu.Lock()
	defer m.mu.Unlock()

	userPlugins, ok := m.usage[userID]
	if !ok {
		userPlugins = make(map[string]PluginUsage)
		m.usage[userID] = userPlugins
	}

	usage := userPlugins[pluginName]
	usage.GPUs += gpuCount
	usage.Services++
	userPlugins[pluginName] = usage

	m.pluginTotal[pluginName] += gpuCount
	m.totalGPUs += gpuCount
}

// ReleaseUsage decrements usage counters when a job stops.
func (m *PluginQuotaManager) ReleaseUsage(userID, pluginName string, gpuCount int) {
	if !m.config.Enabled {
		return
	}

	if userID == "" {
		userID = "anonymous"
	}
	if pluginName == "" {
		pluginName = "default"
	}

	m.mu.Lock()
	defer m.mu.Unlock()

	userPlugins, ok := m.usage[userID]
	if !ok {
		return
	}

	usage := userPlugins[pluginName]
	usage.GPUs -= gpuCount
	usage.Services--

	if usage.GPUs < 0 {
		usage.GPUs = 0
	}
	if usage.Services < 0 {
		usage.Services = 0
	}

	if usage.GPUs == 0 && usage.Services == 0 {
		delete(userPlugins, pluginName)
	} else {
		userPlugins[pluginName] = usage
	}

	if len(userPlugins) == 0 {
		delete(m.usage, userID)
	}

	m.pluginTotal[pluginName] -= gpuCount
	if m.pluginTotal[pluginName] < 0 {
		m.pluginTotal[pluginName] = 0
	}

	m.totalGPUs -= gpuCount
	if m.totalGPUs < 0 {
		m.totalGPUs = 0
	}
}

// GetUsage returns current usage for a user across all plugins.
func (m *PluginQuotaManager) GetUsage(userID string) (map[string]PluginUsage, int) {
	m.mu.RLock()
	defer m.mu.RUnlock()

	if userID == "" {
		userID = "anonymous"
	}

	result := make(map[string]PluginUsage)
	totalGPUs := 0

	if userPlugins, ok := m.usage[userID]; ok {
		for plugin, usage := range userPlugins {
			result[plugin] = usage
			totalGPUs += usage.GPUs
		}
	}

	return result, totalGPUs
}

// GetGlobalUsage returns global GPU usage across all users and plugins.
func (m *PluginQuotaManager) GetGlobalUsage() (int, map[string]int) {
	m.mu.RLock()
	defer m.mu.RUnlock()

	pluginTotals := make(map[string]int, len(m.pluginTotal))
	for k, v := range m.pluginTotal {
		pluginTotals[k] = v
	}

	return m.totalGPUs, pluginTotals
}

// getUserLimit returns the effective limits for a user, applying overrides.
func (m *PluginQuotaManager) getUserLimit(userID string) UserLimit {
	if override, ok := m.config.UserOverrides[userID]; ok {
		return override
	}
	return UserLimit{
		MaxGPUs:     m.config.PerUserGPUs,
		MaxServices: m.config.PerUserServices,
	}
}

// getUsageLocked returns the current usage for a user-plugin combination.
// Must be called with read lock held.
func (m *PluginQuotaManager) getUsageLocked(userID, pluginName string) PluginUsage {
	if userPlugins, ok := m.usage[userID]; ok {
		if usage, ok := userPlugins[pluginName]; ok {
			return usage
		}
	}
	return PluginUsage{}
}