// Package config owns GL configuration loading and validation.
package config

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

	"github.com/knadh/koanf/parsers/toml"
	"github.com/knadh/koanf/providers/file"
	"github.com/knadh/koanf/v2"
)

type Config struct {
	Environment string           `koanf:"environment"`
	GRPC        GRPCConfig       `koanf:"grpc"`
	Database    DatabaseConfig   `koanf:"db"`
	Settlement  SettlementConfig `koanf:"settlement"`
	Telemetry   TelemetryConfig  `koanf:"telemetry"`
}

type DashboardConfig struct {
	Environment string          `koanf:"environment"`
	HTTP        HTTPConfig      `koanf:"http"`
	Database    DatabaseConfig  `koanf:"db"`
	Telemetry   TelemetryConfig `koanf:"telemetry"`
}

type TelemetryConfig struct {
	Enabled         bool              `koanf:"enabled"`
	Protocol        string            `koanf:"protocol"`
	Endpoint        string            `koanf:"endpoint"`
	Insecure        bool              `koanf:"insecure"`
	Headers         map[string]string `koanf:"headers"`
	Sampler         string            `koanf:"sampler"`
	SamplerArg      string            `koanf:"sampler-arg"`
	ExportTimeout   time.Duration     `koanf:"export-timeout"`
	BatchTimeout    time.Duration     `koanf:"batch-timeout"`
	ShutdownTimeout time.Duration     `koanf:"shutdown-timeout"`
}

type GRPCConfig struct {
	Host            string        `koanf:"host"`
	Port            int           `koanf:"port"`
	ShutdownTimeout time.Duration `koanf:"timeout"`
}

type HTTPConfig struct {
	Host              string        `koanf:"host"`
	Port              int           `koanf:"port"`
	ReadHeaderTimeout time.Duration `koanf:"read-header-timeout"`
	ShutdownTimeout   time.Duration `koanf:"shutdown-timeout"`
}

type DatabaseConfig struct {
	Host         string `koanf:"host"`
	Port         int    `koanf:"port"`
	Name         string `koanf:"name"`
	User         string `koanf:"user"`
	Password     string `koanf:"password"`
	GormLogLevel int    `koanf:"gorm-log-level"`
	SSLMode      string `koanf:"-"`
}

type SettlementConfig struct {
	Enabled      bool          `koanf:"enabled"`
	Endpoint     string        `koanf:"endpoint"`
	WorkerID     string        `koanf:"worker-id"`
	PollInterval time.Duration `koanf:"poll-interval"`
	BatchSize    int           `koanf:"batch-size"`
	MaxAttempts  int           `koanf:"max-attempts"`
	AdminToken   string        `koanf:"admin-token"`
}

func Load(path string) (*Config, error) {
	cfg := &Config{
		Environment: "local",
		GRPC: GRPCConfig{
			Host:            "0.0.0.0",
			Port:            8600,
			ShutdownTimeout: 10 * time.Second,
		},
		Database:   defaultDatabaseConfig(),
		Settlement: SettlementConfig{WorkerID: "gl-settlement-1", PollInterval: 5 * time.Second, BatchSize: 20, MaxAttempts: 8},
	}

	if err := load(path, cfg); err != nil {
		return nil, err
	}
	applyEnvironment(&cfg.Database, &cfg.Settlement)
	if err := cfg.Validate(); err != nil {
		return nil, err
	}
	return cfg, nil
}

func LoadDashboard(path string) (*DashboardConfig, error) {
	cfg := &DashboardConfig{
		Environment: "local",
		HTTP: HTTPConfig{
			Host:              "0.0.0.0",
			Port:              8080,
			ReadHeaderTimeout: 5 * time.Second,
			ShutdownTimeout:   10 * time.Second,
		},
		Database: defaultDatabaseConfig(),
	}
	if err := load(path, cfg); err != nil {
		return nil, err
	}
	applyEnvironment(&cfg.Database, nil)
	if err := cfg.Validate(); err != nil {
		return nil, err
	}
	return cfg, nil
}

func applyEnvironment(database *DatabaseConfig, settlement *SettlementConfig) {
	if value, ok := os.LookupEnv("DARANO_GL_DB_PASSWORD"); ok {
		database.Password = value
	}
	if settlement == nil {
		return
	}
	if value, ok := os.LookupEnv("DARANO_GL_SETTLEMENT_ENDPOINT"); ok {
		settlement.Endpoint = strings.TrimRight(value, "/")
	}
	if value, ok := os.LookupEnv("DARANO_GL_ADMIN_TOKEN"); ok {
		settlement.AdminToken = value
	}
}

func load(path string, target any) error {
	k := koanf.New(".")
	if err := k.Load(file.Provider(path), toml.Parser()); err != nil {
		return fmt.Errorf("load config: %w", err)
	}
	if err := k.Unmarshal("", target); err != nil {
		return fmt.Errorf("decode config: %w", err)
	}
	return nil
}

func defaultDatabaseConfig() DatabaseConfig {
	return DatabaseConfig{
		Host:    "127.0.0.1",
		Port:    5432,
		Name:    "gl_db",
		User:    "postgres",
		SSLMode: "disable",
	}
}

func (c *Config) Validate() error {
	if c.GRPC.Host == "" {
		return fmt.Errorf("grpc host is required")
	}
	if c.GRPC.Port < 0 || c.GRPC.Port > 65535 {
		return fmt.Errorf("grpc port must be between 0 and 65535")
	}
	if c.GRPC.ShutdownTimeout <= 0 {
		return fmt.Errorf("grpc shutdown timeout must be positive")
	}
	if c.Environment == "production" && c.Settlement.AdminToken == "" {
		return fmt.Errorf("settlement admin token is required in production")
	}
	return validateDatabase(c.Database)
}

func (c *DashboardConfig) Validate() error {
	if c.HTTP.Host == "" {
		return fmt.Errorf("http host is required")
	}
	if c.HTTP.Port < 0 || c.HTTP.Port > 65535 {
		return fmt.Errorf("http port must be between 0 and 65535")
	}
	if c.HTTP.ReadHeaderTimeout <= 0 || c.HTTP.ShutdownTimeout <= 0 {
		return fmt.Errorf("http timeouts must be positive")
	}
	return validateDatabase(c.Database)
}

func validateDatabase(database DatabaseConfig) error {
	if database.Host == "" || database.Name == "" || database.User == "" {
		return fmt.Errorf("database host, name, and user are required")
	}
	if database.Port < 1 || database.Port > 65535 {
		return fmt.Errorf("database port must be between 1 and 65535")
	}
	return nil
}