package config

import (
	"fmt"
	"os"

	"gopkg.in/yaml.v3"
)

// Load reads and parses an agent config file from the given path.
func Load(path string) (*AgentConfig, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read config %s: %w", path, err)
	}

	// Expand environment variables in the raw YAML bytes.
	expanded := os.ExpandEnv(string(data))

	var cfg AgentConfig
	if err := yaml.Unmarshal([]byte(expanded), &cfg); err != nil {
		return nil, fmt.Errorf("parse config %s: %w", path, err)
	}

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

	return &cfg, nil
}

// LoadMeta reads only the `agent:` block from a config file without expanding
// env vars or running full validation. Used by agentctl list to show all
// agents regardless of whether their env vars are configured.
func LoadMeta(path string) (*AgentConfig, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read config %s: %w", path, err)
	}
	var cfg AgentConfig
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parse config %s: %w", path, err)
	}
	if cfg.Agent.ID == "" {
		return nil, fmt.Errorf("agent.id is required")
	}
	return &cfg, nil
}

// LoadSpecial reads and parses a special agent config file.
// Special agents have no Matrix identity so validation is lighter.
func LoadSpecial(path string) (*SpecialConfig, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read special config %s: %w", path, err)
	}

	expanded := os.ExpandEnv(string(data))

	var cfg SpecialConfig
	if err := yaml.Unmarshal([]byte(expanded), &cfg); err != nil {
		return nil, fmt.Errorf("parse special config %s: %w", path, err)
	}

	if err := validateSpecial(&cfg); err != nil {
		return nil, fmt.Errorf("invalid special config %s: %w", path, err)
	}

	return &cfg, nil
}

// validateSpecial applies sanity checks for special agent configs.
func validateSpecial(cfg *SpecialConfig) error {
	if cfg.Special.ID == "" {
		return fmt.Errorf("special.id is required")
	}
	if cfg.Special.Type == "" {
		return fmt.Errorf("special.type is required")
	}
	if cfg.LLM.Primary.Provider == "" {
		return fmt.Errorf("llm.primary.provider is required")
	}
	return nil
}

// validate applies basic sanity checks.
func validate(cfg *AgentConfig) error {
	if cfg.Agent.ID == "" {
		return fmt.Errorf("agent.id is required")
	}
	if cfg.Matrix.Homeserver == "" {
		return fmt.Errorf("matrix.homeserver is required")
	}
	if cfg.Matrix.UserID == "" {
		return fmt.Errorf("matrix.user_id is required")
	}
	if cfg.LLM.Primary.Provider == "" {
		return fmt.Errorf("llm.primary.provider is required")
	}
	return nil
}