package config

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

	"gopkg.in/yaml.v3"
)

func Load(explicitPath string) (*Config, string, error) {
	path := ResolvePath(explicitPath)

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

	cfg := defaultConfig()
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, path, fmt.Errorf("decode config %q: %w", path, err)
	}

	applyEnvOverrides(&cfg)
	if err := cfg.Validate(); err != nil {
		return nil, path, err
	}

	return &cfg, path, nil
}

func ResolvePath(explicitPath string) string {
	if strings.TrimSpace(explicitPath) != "" {
		return explicitPath
	}

	if envPath := strings.TrimSpace(os.Getenv("OB1_CONFIG")); envPath != "" {
		return envPath
	}

	return DefaultConfigPath
}

func defaultConfig() Config {
	return Config{
		Server: ServerConfig{
			Host:         "0.0.0.0",
			Port:         8080,
			ReadTimeout:  15 * time.Second,
			WriteTimeout: 30 * time.Second,
			IdleTimeout:  60 * time.Second,
		},
		MCP: MCPConfig{
			Path:       "/mcp",
			ServerName: "amcs",
			Version:    "0.1.0",
			Transport:  "streamable_http",
		},
		Auth: AuthConfig{
			Mode:       "api_keys",
			HeaderName: "x-brain-key",
			QueryParam: "key",
		},
		AI: AIConfig{
			Provider: "litellm",
			Embeddings: AIEmbeddingConfig{
				Model:      "openai/text-embedding-3-small",
				Dimensions: 1536,
			},
			Metadata: AIMetadataConfig{
				Model:       "gpt-4o-mini",
				Temperature: 0.1,
			},
			Ollama: OllamaConfig{
				BaseURL: "http://localhost:11434/v1",
				APIKey:  "ollama",
			},
		},
		Capture: CaptureConfig{
			Source: DefaultSource,
			MetadataDefaults: CaptureMetadataDefault{
				Type:          "observation",
				TopicFallback: "uncategorized",
			},
		},
		Search: SearchConfig{
			DefaultLimit:     10,
			DefaultThreshold: 0.5,
			MaxLimit:         50,
		},
		Logging: LoggingConfig{
			Level:  "info",
			Format: "json",
		},
	}
}

func applyEnvOverrides(cfg *Config) {
	overrideString(&cfg.Database.URL, "OB1_DATABASE_URL")
	overrideString(&cfg.AI.LiteLLM.BaseURL, "OB1_LITELLM_BASE_URL")
	overrideString(&cfg.AI.LiteLLM.APIKey, "OB1_LITELLM_API_KEY")
	overrideString(&cfg.AI.Ollama.BaseURL, "OB1_OLLAMA_BASE_URL")
	overrideString(&cfg.AI.Ollama.APIKey, "OB1_OLLAMA_API_KEY")
	overrideString(&cfg.AI.OpenRouter.APIKey, "OB1_OPENROUTER_API_KEY")

	if value, ok := os.LookupEnv("OB1_SERVER_PORT"); ok {
		if port, err := strconv.Atoi(strings.TrimSpace(value)); err == nil {
			cfg.Server.Port = port
		}
	}
}

func overrideString(target *string, envKey string) {
	if value, ok := os.LookupEnv(envKey); ok {
		*target = strings.TrimSpace(value)
	}
}