package config

import (
	"fmt"
	"os"
	"time"

	"gopkg.in/yaml.v3"
)

const (
	maxConfigSize = 10 * 1024 * 1024 // 10MB
)

// Config represents the root configuration structure from .kportal.yaml
type Config struct {
	Contexts    []Context        `yaml:"contexts"`
	HealthCheck *HealthCheckSpec `yaml:"healthCheck,omitempty"`
	Reliability *ReliabilitySpec `yaml:"reliability,omitempty"`
}

// HealthCheckSpec configures health check behavior
type HealthCheckSpec struct {
	Interval         string `yaml:"interval,omitempty"`         // e.g., "3s", "5s"
	Timeout          string `yaml:"timeout,omitempty"`          // e.g., "2s"
	Method           string `yaml:"method,omitempty"`           // "tcp-dial" | "data-transfer"
	MaxConnectionAge string `yaml:"maxConnectionAge,omitempty"` // e.g., "25m" - reconnect before k8s timeout
	MaxIdleTime      string `yaml:"maxIdleTime,omitempty"`      // e.g., "10m" - reconnect if no activity
}

// ReliabilitySpec configures connection reliability features
type ReliabilitySpec struct {
	TCPKeepalive   string `yaml:"tcpKeepalive,omitempty"`   // e.g., "30s" - OS-level keepalive
	DialTimeout    string `yaml:"dialTimeout,omitempty"`    // e.g., "30s" - connection dial timeout
	RetryOnStale   bool   `yaml:"retryOnStale,omitempty"`   // Auto-reconnect on stale detection
	WatchdogPeriod string `yaml:"watchdogPeriod,omitempty"` // e.g., "30s" - goroutine watchdog interval
}

// GetHealthCheckIntervalOrDefault returns the health check interval or default value
func (c *Config) GetHealthCheckIntervalOrDefault() time.Duration {
	if c.HealthCheck != nil && c.HealthCheck.Interval != "" {
		if d, err := time.ParseDuration(c.HealthCheck.Interval); err == nil {
			return d
		}
	}
	return 3 * time.Second // Default: check every 3 seconds
}

// GetHealthCheckTimeoutOrDefault returns the health check timeout or default value
func (c *Config) GetHealthCheckTimeoutOrDefault() time.Duration {
	if c.HealthCheck != nil && c.HealthCheck.Timeout != "" {
		if d, err := time.ParseDuration(c.HealthCheck.Timeout); err == nil {
			return d
		}
	}
	return 2 * time.Second // Default: 2 second timeout
}

// GetHealthCheckMethod returns the health check method or default
func (c *Config) GetHealthCheckMethod() string {
	if c.HealthCheck != nil && c.HealthCheck.Method != "" {
		return c.HealthCheck.Method
	}
	return "data-transfer" // Default: more reliable data transfer test
}

// GetMaxConnectionAge returns the max connection age or default
func (c *Config) GetMaxConnectionAge() time.Duration {
	if c.HealthCheck != nil && c.HealthCheck.MaxConnectionAge != "" {
		if d, err := time.ParseDuration(c.HealthCheck.MaxConnectionAge); err == nil {
			return d
		}
	}
	return 25 * time.Minute // Default: 25 minutes (before typical 30min k8s timeout)
}

// GetMaxIdleTime returns the max idle time or default
func (c *Config) GetMaxIdleTime() time.Duration {
	if c.HealthCheck != nil && c.HealthCheck.MaxIdleTime != "" {
		if d, err := time.ParseDuration(c.HealthCheck.MaxIdleTime); err == nil {
			return d
		}
	}
	return 10 * time.Minute // Default: 10 minutes idle before reconnect
}

// GetTCPKeepalive returns the TCP keepalive duration or default
func (c *Config) GetTCPKeepalive() time.Duration {
	if c.Reliability != nil && c.Reliability.TCPKeepalive != "" {
		if d, err := time.ParseDuration(c.Reliability.TCPKeepalive); err == nil {
			return d
		}
	}
	return 30 * time.Second // Default: 30 second keepalive
}

// GetRetryOnStale returns whether to retry on stale connections
func (c *Config) GetRetryOnStale() bool {
	if c.Reliability != nil {
		return c.Reliability.RetryOnStale
	}
	return true // Default: enabled
}

// GetWatchdogPeriod returns the goroutine watchdog check period or default
func (c *Config) GetWatchdogPeriod() time.Duration {
	if c.Reliability != nil && c.Reliability.WatchdogPeriod != "" {
		if d, err := time.ParseDuration(c.Reliability.WatchdogPeriod); err == nil {
			return d
		}
	}
	return 30 * time.Second // Default: check every 30 seconds
}

// GetDialTimeout returns the connection dial timeout or default
func (c *Config) GetDialTimeout() time.Duration {
	if c.Reliability != nil && c.Reliability.DialTimeout != "" {
		if d, err := time.ParseDuration(c.Reliability.DialTimeout); err == nil {
			return d
		}
	}
	return 30 * time.Second // Default: 30 second dial timeout
}

// Context represents a Kubernetes context with its namespaces
type Context struct {
	Name       string      `yaml:"name"`
	Namespaces []Namespace `yaml:"namespaces"`
}

// Namespace represents a Kubernetes namespace with its forwards
type Namespace struct {
	Name     string    `yaml:"name"`
	Forwards []Forward `yaml:"forwards"`
}

// Forward represents a single port-forward configuration
type Forward struct {
	Resource  string `yaml:"resource"`        // e.g., "pod/my-app", "service/postgres", "pod"
	Selector  string `yaml:"selector"`        // Label selector for pod resolution (e.g., "app=nginx,env=prod")
	Protocol  string `yaml:"protocol"`        // tcp or udp
	Port      int    `yaml:"port"`            // Remote port
	LocalPort int    `yaml:"localPort"`       // Local port
	Alias     string `yaml:"alias,omitempty"` // Optional human-readable alias for this forward

	// Runtime fields (not in YAML)
	contextName   string
	namespaceName string
}

// ID returns a unique identifier for this forward configuration.
// Format: alias:localPort (if alias provided) or context/namespace/resource:localPort
func (f *Forward) ID() string {
	if f.Alias != "" {
		return fmt.Sprintf("%s:%d", f.Alias, f.LocalPort)
	}
	return fmt.Sprintf("%s/%s/%s:%d", f.contextName, f.namespaceName, f.Resource, f.LocalPort)
}

// String returns a human-readable representation of the forward.
// Format: alias:port→localPort (if alias provided) or context/namespace/resource:port→localPort
func (f *Forward) String() string {
	if f.Alias != "" {
		return fmt.Sprintf("%s:%d→%d", f.Alias, f.Port, f.LocalPort)
	}
	if f.Selector != "" {
		return fmt.Sprintf("%s/%s/%s[%s]:%d→%d",
			f.contextName, f.namespaceName, f.Resource, f.Selector, f.Port, f.LocalPort)
	}
	return fmt.Sprintf("%s/%s/%s:%d→%d",
		f.contextName, f.namespaceName, f.Resource, f.Port, f.LocalPort)
}

// SetContext sets the context and namespace names for this forward.
// This is used during config parsing to populate runtime fields.
func (f *Forward) SetContext(ctx, ns string) {
	f.contextName = ctx
	f.namespaceName = ns
}

// GetContext returns the context name for this forward.
func (f *Forward) GetContext() string {
	return f.contextName
}

// GetNamespace returns the namespace name for this forward.
func (f *Forward) GetNamespace() string {
	return f.namespaceName
}

// LoadConfig loads and parses the configuration file from the given path.
func LoadConfig(path string) (*Config, error) {
	// Validate file size before reading
	fileInfo, err := os.Stat(path)
	if err != nil {
		return nil, fmt.Errorf("failed to stat config file: %w", err)
	}

	if fileInfo.Size() > maxConfigSize {
		return nil, fmt.Errorf("config file too large: %d bytes (max %d)", fileInfo.Size(), maxConfigSize)
	}

	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("failed to read config file: %w", err)
	}

	return ParseConfig(data)
}

// ParseConfig parses YAML configuration data into a Config struct.
func ParseConfig(data []byte) (*Config, error) {
	var cfg Config
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("failed to parse YAML: %w", err)
	}

	// Populate runtime fields (context and namespace names)
	for i := range cfg.Contexts {
		ctx := &cfg.Contexts[i]
		for j := range ctx.Namespaces {
			ns := &ctx.Namespaces[j]
			for k := range ns.Forwards {
				fwd := &ns.Forwards[k]
				fwd.SetContext(ctx.Name, ns.Name)
			}
		}
	}

	return &cfg, nil
}

// GetAllForwards returns a flat list of all forwards across all contexts and namespaces.
func (c *Config) GetAllForwards() []Forward {
	var forwards []Forward

	for _, ctx := range c.Contexts {
		for _, ns := range ctx.Namespaces {
			forwards = append(forwards, ns.Forwards...)
		}
	}

	return forwards
}