package config

import (
	"fmt"
	"os"
	"time"

	"gopkg.in/yaml.v3"
)

// Config represents the Staff MVP configuration
type Config struct {
	OpenAI OpenAIConfig  `yaml:"openai"`
	GitHub GitHubConfig  `yaml:"github"`
	Gerrit GerritConfig  `yaml:"gerrit"`
	Agents []AgentConfig `yaml:"agents"`
	Tasks  TasksConfig   `yaml:"tasks"`
	Git    GitConfig     `yaml:"git"`
}

// OpenAIConfig represents OpenAI provider configuration
type OpenAIConfig struct {
	APIKey     string        `yaml:"api_key"`
	Model      string        `yaml:"model"`
	BaseURL    string        `yaml:"base_url"`
	Timeout    time.Duration `yaml:"timeout"`
	MaxRetries int           `yaml:"max_retries"`
}

// GitHubConfig represents GitHub integration configuration
type GitHubConfig struct {
	Token string `yaml:"token"`
	Owner string `yaml:"owner"`
	Repo  string `yaml:"repo"`
}

// GerritConfig represents Gerrit integration configuration
type GerritConfig struct {
	Username string `yaml:"username"`
	Password string `yaml:"password"` // HTTP password or API token
	BaseURL  string `yaml:"base_url"` // Gerrit server URL (e.g. https://gerrit.example.com)
	Project  string `yaml:"project"`  // Gerrit project name
}

// AgentConfig represents individual agent configuration
type AgentConfig struct {
	Name             string   `yaml:"name"`
	Role             string   `yaml:"role"`
	Model            string   `yaml:"model"`
	SystemPromptFile string   `yaml:"system_prompt_file"`
	Capabilities     []string `yaml:"capabilities"` // For auto-assignment
	TaskTypes        []string `yaml:"task_types"`   // Types of tasks this agent handles
	MaxTokens        *int     `yaml:"max_tokens"`   // Model-specific token limits
	Temperature      *float64 `yaml:"temperature"`  // Model creativity setting
}

// TasksConfig represents task management configuration
type TasksConfig struct {
	StoragePath   string `yaml:"storage_path"`
	CompletedPath string `yaml:"completed_path"`
}

// GitConfig represents Git operation configuration
type GitConfig struct {
	BranchPrefix          string `yaml:"branch_prefix"`
	CommitMessageTemplate string `yaml:"commit_message_template"`
	PRTemplate            string `yaml:"pr_template"`
}

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

	// Parse YAML
	var config Config
	if err := yaml.Unmarshal(data, &config); err != nil {
		return nil, fmt.Errorf("failed to parse config YAML: %w", err)
	}

	// Apply defaults
	config = applyDefaults(config)

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

	return &config, nil
}

// LoadConfigWithEnvOverrides loads config with environment variable overrides
func LoadConfigWithEnvOverrides(configPath string) (*Config, error) {
	config, err := LoadConfig(configPath)
	if err != nil {
		return nil, err
	}

	// Override with environment variables if present
	if apiKey := os.Getenv("OPENAI_API_KEY"); apiKey != "" {
		config.OpenAI.APIKey = apiKey
	}
	if githubToken := os.Getenv("GITHUB_TOKEN"); githubToken != "" {
		config.GitHub.Token = githubToken
	}
	if owner := os.Getenv("GITHUB_OWNER"); owner != "" {
		config.GitHub.Owner = owner
	}
	if repo := os.Getenv("GITHUB_REPO"); repo != "" {
		config.GitHub.Repo = repo
	}
	if gerritUsername := os.Getenv("GERRIT_USERNAME"); gerritUsername != "" {
		config.Gerrit.Username = gerritUsername
	}
	if gerritPassword := os.Getenv("GERRIT_PASSWORD"); gerritPassword != "" {
		config.Gerrit.Password = gerritPassword
	}
	if gerritBaseURL := os.Getenv("GERRIT_BASE_URL"); gerritBaseURL != "" {
		config.Gerrit.BaseURL = gerritBaseURL
	}
	if gerritProject := os.Getenv("GERRIT_PROJECT"); gerritProject != "" {
		config.Gerrit.Project = gerritProject
	}

	// Re-validate after env overrides
	if err := validateConfig(*config); err != nil {
		return nil, fmt.Errorf("invalid configuration after env overrides: %w", err)
	}

	return config, nil
}

// applyDefaults applies default values to configuration
func applyDefaults(config Config) Config {
	// OpenAI defaults
	if config.OpenAI.Model == "" {
		config.OpenAI.Model = "gpt-4"
	}
	if config.OpenAI.BaseURL == "" {
		config.OpenAI.BaseURL = "https://api.openai.com/v1"
	}
	if config.OpenAI.Timeout == 0 {
		config.OpenAI.Timeout = 30 * time.Second
	}
	if config.OpenAI.MaxRetries == 0 {
		config.OpenAI.MaxRetries = 3
	}

	// Tasks defaults
	if config.Tasks.StoragePath == "" {
		config.Tasks.StoragePath = "../operations/"
	}
	if config.Tasks.CompletedPath == "" {
		config.Tasks.CompletedPath = "../operations/completed/"
	}

	// Git defaults
	if config.Git.BranchPrefix == "" {
		config.Git.BranchPrefix = "task/"
	}
	if config.Git.CommitMessageTemplate == "" {
		config.Git.CommitMessageTemplate = "Task {task_id}: {task_title}\n\n{solution}\n\nGenerated by Staff AI Agent: {agent_name}"
	}
	if config.Git.PRTemplate == "" {
		config.Git.PRTemplate = `## Task: {task_title}

**Task ID:** {task_id}  
**Agent:** {agent_name}  
**Priority:** {priority}

### Description
{task_description}

### Solution
{solution}

### Files Changed
{files_changed}

---
*Generated by Staff AI Multi-Agent System*`
	}

	// Agent defaults
	for i := range config.Agents {
		if config.Agents[i].Model == "" {
			config.Agents[i].Model = config.OpenAI.Model
		}
	}

	return config
}

// validateConfig validates the configuration
func validateConfig(config Config) error {
	// Validate OpenAI config
	if config.OpenAI.APIKey == "" {
		return fmt.Errorf("openai.api_key is required")
	}
	if config.OpenAI.Model == "" {
		return fmt.Errorf("openai.model is required")
	}

	// Validate that at least one Git provider is configured
	hasGitHub := config.GitHub.Token != "" && config.GitHub.Owner != "" && config.GitHub.Repo != ""
	hasGerrit := config.Gerrit.Username != "" && config.Gerrit.Password != "" && config.Gerrit.BaseURL != "" && config.Gerrit.Project != ""
	
	if !hasGitHub && !hasGerrit {
		return fmt.Errorf("either GitHub or Gerrit configuration is required")
	}
	
	// Validate GitHub config if provided
	if config.GitHub.Token != "" {
		if config.GitHub.Owner == "" {
			return fmt.Errorf("github.owner is required when github.token is provided")
		}
		if config.GitHub.Repo == "" {
			return fmt.Errorf("github.repo is required when github.token is provided")
		}
	}
	
	// Validate Gerrit config if provided
	if config.Gerrit.Username != "" {
		if config.Gerrit.Password == "" {
			return fmt.Errorf("gerrit.password is required when gerrit.username is provided")
		}
		if config.Gerrit.BaseURL == "" {
			return fmt.Errorf("gerrit.base_url is required when gerrit.username is provided")
		}
		if config.Gerrit.Project == "" {
			return fmt.Errorf("gerrit.project is required when gerrit.username is provided")
		}
	}

	// Validate agents
	if len(config.Agents) == 0 {
		return fmt.Errorf("at least one agent must be configured")
	}

	for i, agent := range config.Agents {
		if agent.Name == "" {
			return fmt.Errorf("agent[%d].name is required", i)
		}
		if agent.Role == "" {
			return fmt.Errorf("agent[%d].role is required", i)
		}
		if agent.SystemPromptFile == "" {
			return fmt.Errorf("agent[%d].system_prompt_file is required", i)
		}
	}

	return nil
}

// GetAgentByName returns an agent config by name
func (c *Config) GetAgentByName(name string) (*AgentConfig, error) {
	for _, agent := range c.Agents {
		if agent.Name == name {
			return &agent, nil
		}
	}
	return nil, fmt.Errorf("agent not found: %s", name)
}

// ListAgentNames returns a list of all configured agent names
func (c *Config) ListAgentNames() []string {
	names := make([]string, len(c.Agents))
	for i, agent := range c.Agents {
		names[i] = agent.Name
	}
	return names
}

// HasGitHubConfig returns true if GitHub is properly configured
func (c *Config) HasGitHubConfig() bool {
	return c.GitHub.Token != "" && c.GitHub.Owner != "" && c.GitHub.Repo != ""
}

// HasGerritConfig returns true if Gerrit is properly configured
func (c *Config) HasGerritConfig() bool {
	return c.Gerrit.Username != "" && c.Gerrit.Password != "" && c.Gerrit.BaseURL != "" && c.Gerrit.Project != ""
}

// GetPrimaryGitProvider returns the primary git provider type ("github" or "gerrit")
// If both are configured, GitHub takes precedence for backward compatibility
func (c *Config) GetPrimaryGitProvider() string {
	if c.HasGitHubConfig() {
		return "github"
	}
	if c.HasGerritConfig() {
		return "gerrit"
	}
	return ""
}