package config

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

	"github.com/spf13/viper"
)

type Config struct {
	Server     ServerConfig     `mapstructure:"server"`
	Database   DatabaseConfig   `mapstructure:"database"`
	Redis      RedisConfig      `mapstructure:"redis"`
	Cache      CacheConfig      `mapstructure:"cache"`
	JWT        JWTConfig        `mapstructure:"jwt"`
	Log        LogConfig        `mapstructure:"log"`
	LLM        LLMConfig        `mapstructure:"llm"`
	Generation GenerationConfig `mapstructure:"generation"`
}

type ServerConfig struct {
	Port int    `mapstructure:"port"`
	Mode string `mapstructure:"mode"`
}

type DatabaseConfig struct {
	Host         string `mapstructure:"host"`
	Port         int    `mapstructure:"port"`
	User         string `mapstructure:"user"`
	Password     string `mapstructure:"password"`
	DBName       string `mapstructure:"dbname"`
	SSLMode      string `mapstructure:"sslmode"`
	MaxOpenConns int    `mapstructure:"max_open_conns"`
	MaxIdleConns int    `mapstructure:"max_idle_conns"`
}

func (d DatabaseConfig) DSN() string {
	return fmt.Sprintf("postgres://%s:%s@%s:%d/%s?sslmode=%s",
		d.User, d.Password, d.Host, d.Port, d.DBName, d.SSLMode)
}

type RedisConfig struct {
	Addr string `mapstructure:"addr"`
	DB   int    `mapstructure:"db"`
}

type JWTConfig struct {
	Secret     string        `mapstructure:"secret"`
	AccessTTL  time.Duration `mapstructure:"access_ttl"`
	RefreshTTL time.Duration `mapstructure:"refresh_ttl"`
}

type LogConfig struct {
	Level  string `mapstructure:"level"`
	Format string `mapstructure:"format"`
}

type LLMConfig struct {
	Provider        string        `mapstructure:"provider"`
	APIKey          string        `mapstructure:"api_key"`
	BaseURL         string        `mapstructure:"base_url"`
	Model           string        `mapstructure:"model"`
	Timeout         time.Duration `mapstructure:"timeout"`
	MaxOutputTokens int64         `mapstructure:"max_output_tokens"`
	Temperature     float64       `mapstructure:"temperature"`
	TopP            float64       `mapstructure:"top_p"`
	ReasoningEffort string        `mapstructure:"reasoning_effort"`
	WebSearchLimit  int32         `mapstructure:"web_search_limit"`
}

type CacheConfig struct {
	Driver string `mapstructure:"driver"` // "redis" or "memory"
}

type GenerationConfig struct {
	QueueSize         int           `mapstructure:"queue_size"`
	WorkerConcurrency int           `mapstructure:"worker_concurrency"`
	StreamEnabled     bool          `mapstructure:"stream_enabled"`
	ArticleTimeout    time.Duration `mapstructure:"article_timeout"`
}

func Load(configPath string) (*Config, error) {
	v := viper.New()
	v.SetConfigFile(configPath)
	v.AutomaticEnv()
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))

	if err := v.ReadInConfig(); err != nil {
		return nil, fmt.Errorf("read config: %w", err)
	}

	// Allow local overrides
	v.SetConfigFile(strings.Replace(configPath, ".yaml", ".local.yaml", 1))
	_ = v.MergeInConfig()

	var cfg Config
	if err := v.Unmarshal(&cfg); err != nil {
		return nil, fmt.Errorf("unmarshal config: %w", err)
	}

	applyEnvOverrides(&cfg)

	return &cfg, nil
}

func applyEnvOverrides(cfg *Config) {
	if cfg == nil {
		return
	}

	if apiKey, ok := lookupNonEmptyEnv("LLM_API_KEY"); ok {
		cfg.LLM.APIKey = apiKey
	}
}

func lookupNonEmptyEnv(key string) (string, bool) {
	value, ok := os.LookupEnv(key)
	if !ok {
		return "", false
	}

	value = strings.TrimSpace(value)
	if value == "" {
		return "", false
	}

	return value, true
}