package config

import (
	"errors"
	"fmt"
	"os"
	"strconv"
	"time"
)

// ServerConfig holds the runtime options for the proxy server. Fields map to
// CLI flags and (for LogLevel and BaseURL) the OLLAMA_PROXY_* environment
// variables, so a systemd unit can set defaults without changing the binary.
type ServerConfig struct {
	Addr     string        // listen address, e.g. "127.0.0.1:11435"
	BaseURL  string        // upstream Ollama Cloud root, e.g. "https://ollama.com"
	Cooldown time.Duration // per-account 429 cooldown window
	Retries  int           // max failover attempts (= number of accounts)
	LogLevel string        // debug | info | warn | error
}

// DefaultServerConfig returns the canonical defaults used when a flag or env
// var is not set.
func DefaultServerConfig() ServerConfig {
	return ServerConfig{
		Addr:     "127.0.0.1:11435",
		BaseURL:  "https://ollama.com",
		Cooldown: 60 * time.Second,
		Retries:  3,
		LogLevel: "info",
	}
}

// ApplyEnv overlays OLLAMA_PROXY_* environment variables on top of the current
// config. Empty / unparsable env vars are ignored (the existing value wins).
func (c *ServerConfig) ApplyEnv() {
	if v := os.Getenv("OLLAMA_PROXY_ADDR"); v != "" {
		c.Addr = v
	}
	if v := os.Getenv("OLLAMA_PROXY_BASE_URL"); v != "" {
		c.BaseURL = v
	}
	if v := os.Getenv("OLLAMA_PROXY_COOLDOWN"); v != "" {
		if d, err := time.ParseDuration(v); err == nil {
			c.Cooldown = d
		}
	}
	if v := os.Getenv("OLLAMA_PROXY_RETRIES"); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n > 0 {
			c.Retries = n
		}
	}
	if v := os.Getenv("OLLAMA_PROXY_LOG_LEVEL"); v != "" {
		switch v {
		case "debug", "info", "warn", "error":
			c.LogLevel = v
		}
	}
}

// Validate returns an error when a field has an obviously invalid value.
func (c *ServerConfig) Validate() error {
	if c.Addr == "" {
		return errors.New("addr is required")
	}
	if c.BaseURL == "" {
		return errors.New("base_url is required")
	}
	if !startsWithScheme(c.BaseURL, "http://") && !startsWithScheme(c.BaseURL, "https://") {
		return fmt.Errorf("base_url must start with http:// or https://, got %q", c.BaseURL)
	}
	if c.Cooldown < 0 {
		return errors.New("cooldown must be >= 0")
	}
	if c.Retries < 1 {
		return errors.New("retries must be >= 1")
	}
	switch c.LogLevel {
	case "debug", "info", "warn", "error":
	default:
		return fmt.Errorf("log_level must be one of debug|info|warn|error, got %q", c.LogLevel)
	}
	return nil
}

func startsWithScheme(s, scheme string) bool {
	if len(s) < len(scheme) {
		return false
	}
	return s[:len(scheme)] == scheme
}