// Package providers maps AI requests and answers to each provider's wire
// format: the OpenAI-compatible chat completions API and the Anthropic
// Messages API. The adapters only build and parse JSON; the AI service in
// classes/services sends the requests through the framework's guarded
// outbound client.
package providers

import (
	"net/http"
	"strconv"
	"strings"

	"git.golem15.com/golem15/sm-golem-plugin/classes/valueobjects"
	"git.golem15.com/golem15/summercms/modules/fetchguard"
)

// Adapter is one provider's mapping (PHP AIProviderAdapter).
type Adapter interface {
	// Headers are the provider's auth and version headers for apiKey.
	Headers(apiKey string) http.Header
	// ChatEndpoint is the chat URL under baseURL ("" means the
	// provider's default base URL).
	ChatEndpoint(baseURL string) string
	// FilesEndpoint is the file upload URL under baseURL.
	FilesEndpoint(baseURL string) string
	// ImageEndpoint is the image generation URL, "" when the provider
	// has none.
	ImageEndpoint(baseURL string) string
	// BuildChatPayload is the chat request body for prompt, with modelID
	// unless the prompt overrides the model.
	BuildChatPayload(prompt valueobjects.Prompt, modelID string) *valueobjects.Payload
	// FileUploadFields are the plain multipart fields of a file upload.
	FileUploadFields(purpose string) []fetchguard.FormField
	// FileUploadHeaders are the headers of a file upload.
	FileUploadHeaders(apiKey string) http.Header
	// ParseChatResponse maps a decoded chat answer to an AIResponse.
	ParseChatResponse(data map[string]any) valueobjects.AIResponse
	// ParseStreamChunk reads one server-sent-events line: the content
	// delta it carries ("" when none) and whether the stream ended.
	ParseStreamChunk(line string) (delta string, done bool)
}

// Default base URLs, used when a config leaves base_url empty.
const (
	OpenAIBaseURL    = "https://api.openai.com/v1"
	AnthropicBaseURL = "https://api.anthropic.com/v1"
)

// ForName is ProviderFactory::make: the Anthropic adapter for "anthropic",
// the OpenAI-compatible adapter for anything else.
func ForName(adapter string) Adapter {
	if adapter == "anthropic" {
		return AnthropicAdapter{}
	}
	return OpenAIAdapter{}
}

// endpoint is rtrim(base, '/') . path, with def standing in for an empty
// base.
func endpoint(base, def, path string) string {
	if base == "" {
		base = def
	}
	return strings.TrimRight(base, "/") + path
}

// dig walks nested JSON objects and arrays (PHP $a['x'][0]['y'] ?? null).
func dig(v any, path ...any) any {
	for _, p := range path {
		switch key := p.(type) {
		case string:
			m, ok := v.(map[string]any)
			if !ok {
				return nil
			}
			v = m[key]
		case int:
			s, ok := v.([]any)
			if !ok || key < 0 || key >= len(s) {
				return nil
			}
			v = s[key]
		default:
			return nil
		}
	}
	return v
}

// errorMessage is PHP's `$data['error']['message'] ?? 'Unknown API
// error'` for a response that carries an error key, and false otherwise.
func errorMessage(data map[string]any) (string, bool) {
	e, ok := data["error"]
	if !ok || e == nil {
		return "", false
	}
	if msg := dig(e, "message"); msg != nil {
		return phpString(msg), true
	}
	return "Unknown API error", true
}

// phpString is a PHP string cast of a decoded JSON scalar.
func phpString(v any) string {
	switch t := v.(type) {
	case string:
		return t
	case bool:
		if t {
			return "1"
		}
		return ""
	case float64:
		return strconv.FormatFloat(t, 'f', -1, 64)
	}
	return ""
}