package config

import (
	"fmt"
	"os"
	"strings"
	"time"

	"gopkg.in/yaml.v3"
)

// Config holds the complete application configuration.
type Config struct {
	Service     ServiceConfig     `yaml:"service"`
	Inputs      InputsConfig      `yaml:"inputs"`
	Outputs     OutputsConfig     `yaml:"outputs"`
	Correlation CorrelationConfig `yaml:"correlation"`
}

// ServiceConfig holds service-level configuration.
type ServiceConfig struct {
	Name     string `yaml:"name"`
	Language string `yaml:"language"`
}

// InputsConfig holds input sources configuration.
type InputsConfig struct {
	UnixSockets []UnixSocketConfig `yaml:"unix_sockets"`
}

// UnixSocketConfig holds a Unix socket source configuration.
type UnixSocketConfig struct {
	Name   string `yaml:"name"`
	Path   string `yaml:"path"`
	Format string `yaml:"format"`
}

// OutputsConfig holds output sinks configuration.
type OutputsConfig struct {
	File       FileOutputConfig       `yaml:"file"`
	ClickHouse ClickHouseOutputConfig `yaml:"clickhouse"`
	Stdout     StdoutOutputConfig     `yaml:"stdout"`
}

// FileOutputConfig holds file sink configuration.
type FileOutputConfig struct {
	Enabled bool   `yaml:"enabled"`
	Path    string `yaml:"path"`
}

// ClickHouseOutputConfig holds ClickHouse sink configuration.
type ClickHouseOutputConfig struct {
	Enabled         bool   `yaml:"enabled"`
	DSN             string `yaml:"dsn"`
	Table           string `yaml:"table"`
	BatchSize       int    `yaml:"batch_size"`
	FlushIntervalMs int    `yaml:"flush_interval_ms"`
	MaxBufferSize   int    `yaml:"max_buffer_size"`
	DropOnOverflow  bool   `yaml:"drop_on_overflow"`
	AsyncInsert     bool   `yaml:"async_insert"`
	TimeoutMs       int    `yaml:"timeout_ms"`
}

// StdoutOutputConfig holds stdout sink configuration.
type StdoutOutputConfig struct {
	Enabled bool `yaml:"enabled"`
}

// CorrelationConfig holds correlation configuration.
type CorrelationConfig struct {
	Key          []string           `yaml:"key"`
	TimeWindow   TimeWindowConfig   `yaml:"time_window"`
	OrphanPolicy OrphanPolicyConfig `yaml:"orphan_policy"`
}

// TimeWindowConfig holds time window configuration.
type TimeWindowConfig struct {
	Value int    `yaml:"value"`
	Unit  string `yaml:"unit"`
}

// OrphanPolicyConfig holds orphan event policy configuration.
type OrphanPolicyConfig struct {
	ApacheAlwaysEmit bool `yaml:"apache_always_emit"`
	NetworkEmit      bool `yaml:"network_emit"`
}

// Load loads configuration from a YAML file.
func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("failed to read config file: %w", err)
	}

	cfg := defaultConfig()

	if err := yaml.Unmarshal(data, cfg); err != nil {
		return nil, fmt.Errorf("failed to parse config file: %w", err)
	}

	if err := cfg.Validate(); err != nil {
		return nil, fmt.Errorf("invalid config: %w", err)
	}

	return cfg, nil
}

// defaultConfig returns a Config with default values.
func defaultConfig() *Config {
	return &Config{
		Service: ServiceConfig{
			Name:     "logcorrelator",
			Language: "go",
		},
		Inputs: InputsConfig{
			UnixSockets: make([]UnixSocketConfig, 0),
		},
		Outputs: OutputsConfig{
			File: FileOutputConfig{
				Enabled: true,
				Path:    "/var/log/logcorrelator/correlated.log",
			},
			ClickHouse: ClickHouseOutputConfig{
				Enabled:         false,
				BatchSize:       500,
				FlushIntervalMs: 200,
				MaxBufferSize:   5000,
				DropOnOverflow:  true,
				AsyncInsert:     true,
				TimeoutMs:       1000,
			},
			Stdout: StdoutOutputConfig{
				Enabled: false,
			},
		},
		Correlation: CorrelationConfig{
			Key: []string{"src_ip", "src_port"},
			TimeWindow: TimeWindowConfig{
				Value: 1,
				Unit:  "s",
			},
			OrphanPolicy: OrphanPolicyConfig{
				ApacheAlwaysEmit: true,
				NetworkEmit:      false,
			},
		},
	}
}

// Validate validates the configuration.
func (c *Config) Validate() error {
	if len(c.Inputs.UnixSockets) < 2 {
		return fmt.Errorf("at least two unix socket inputs are required")
	}

	seenNames := make(map[string]struct{}, len(c.Inputs.UnixSockets))
	seenPaths := make(map[string]struct{}, len(c.Inputs.UnixSockets))

	for i, input := range c.Inputs.UnixSockets {
		if strings.TrimSpace(input.Name) == "" {
			return fmt.Errorf("inputs.unix_sockets[%d].name is required", i)
		}
		if strings.TrimSpace(input.Path) == "" {
			return fmt.Errorf("inputs.unix_sockets[%d].path is required", i)
		}

		if _, exists := seenNames[input.Name]; exists {
			return fmt.Errorf("duplicate unix socket input name: %s", input.Name)
		}
		seenNames[input.Name] = struct{}{}

		if _, exists := seenPaths[input.Path]; exists {
			return fmt.Errorf("duplicate unix socket input path: %s", input.Path)
		}
		seenPaths[input.Path] = struct{}{}
	}

	if !c.Outputs.File.Enabled && !c.Outputs.ClickHouse.Enabled && !c.Outputs.Stdout.Enabled {
		return fmt.Errorf("at least one output must be enabled")
	}

	if c.Outputs.File.Enabled && strings.TrimSpace(c.Outputs.File.Path) == "" {
		return fmt.Errorf("file output path is required when file output is enabled")
	}

	if c.Outputs.ClickHouse.Enabled {
		if strings.TrimSpace(c.Outputs.ClickHouse.DSN) == "" {
			return fmt.Errorf("clickhouse DSN is required when enabled")
		}
		if strings.TrimSpace(c.Outputs.ClickHouse.Table) == "" {
			return fmt.Errorf("clickhouse table is required when enabled")
		}
		if c.Outputs.ClickHouse.BatchSize <= 0 {
			return fmt.Errorf("clickhouse batch_size must be > 0")
		}
		if c.Outputs.ClickHouse.MaxBufferSize <= 0 {
			return fmt.Errorf("clickhouse max_buffer_size must be > 0")
		}
		if c.Outputs.ClickHouse.TimeoutMs <= 0 {
			return fmt.Errorf("clickhouse timeout_ms must be > 0")
		}
	}

	if len(c.Correlation.Key) == 0 {
		return fmt.Errorf("correlation.key cannot be empty")
	}
	if c.Correlation.TimeWindow.Value <= 0 {
		return fmt.Errorf("correlation.time_window.value must be > 0")
	}

	return nil
}

// GetTimeWindow returns the time window as a duration.
func (c *CorrelationConfig) GetTimeWindow() time.Duration {
	value := c.TimeWindow.Value
	if value <= 0 {
		value = 1
	}

	unit := c.TimeWindow.Unit
	if unit == "" {
		unit = "s"
	}

	switch unit {
	case "ms", "millisecond", "milliseconds":
		return time.Duration(value) * time.Millisecond
	case "s", "second", "seconds":
		return time.Duration(value) * time.Second
	case "m", "minute", "minutes":
		return time.Duration(value) * time.Minute
	default:
		return time.Duration(value) * time.Second
	}
}