package providers

import (
	"encoding/json"
	"net/http"
	"regexp"
	"strings"

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

// OpenAIAdapter is the OpenAI-compatible chat completions mapping (PHP
// OpenAIAdapter). It also serves compatible providers (Groq, Together,
// local model servers) through their base URL.
type OpenAIAdapter struct{}

var _ Adapter = OpenAIAdapter{}

// reasoningModel matches the o-series and gpt-5 model ids, which spend
// completion tokens on hidden reasoning.
var reasoningModel = regexp.MustCompile(`(?i)^(o\d|gpt-5)`)

// Headers is Authorization: Bearer <key>.
func (OpenAIAdapter) Headers(apiKey string) http.Header {
	return http.Header{"Authorization": {fetchguard.Bearer(apiKey)}}
}

// ChatEndpoint is <base>/chat/completions.
func (OpenAIAdapter) ChatEndpoint(baseURL string) string {
	return endpoint(baseURL, OpenAIBaseURL, "/chat/completions")
}

// FilesEndpoint is <base>/files.
func (OpenAIAdapter) FilesEndpoint(baseURL string) string {
	return endpoint(baseURL, OpenAIBaseURL, "/files")
}

// ImageEndpoint is <base>/images/generations.
func (OpenAIAdapter) ImageEndpoint(baseURL string) string {
	return endpoint(baseURL, OpenAIBaseURL, "/images/generations")
}

// BuildChatPayload is the prompt's chat completions body with three
// adjustments PHP makes: response_format is dropped (recognition asks for
// JSON in the prompt instead), a max_tokens option becomes
// max_completion_tokens (an explicit max_completion_tokens wins), and an
// o-series or gpt-5 model gets reasoning_effort low unless the prompt set
// one.
func (OpenAIAdapter) BuildChatPayload(prompt valueobjects.Prompt, modelID string) *valueobjects.Payload {
	payload := prompt.ToAPIPayload(modelID)
	payload.Delete("response_format")
	if payload.IsSet("max_tokens") || payload.IsSet("max_completion_tokens") {
		v, _ := payload.Get("max_completion_tokens")
		if v == nil {
			v, _ = payload.Get("max_tokens")
		}
		payload.Set("max_completion_tokens", v)
		payload.Delete("max_tokens")
	}
	if reasoningModel.MatchString(modelID) && !payload.IsSet("reasoning_effort") {
		payload.Set("reasoning_effort", "low")
	}
	return payload
}

// FileUploadFields is the purpose field.
func (OpenAIAdapter) FileUploadFields(purpose string) []fetchguard.FormField {
	return []fetchguard.FormField{{Name: "purpose", Value: purpose}}
}

// FileUploadHeaders is Authorization: Bearer <key>.
func (OpenAIAdapter) FileUploadHeaders(apiKey string) http.Header {
	return http.Header{"Authorization": {fetchguard.Bearer(apiKey)}}
}

// ParseChatResponse reads choices[0].message.content; an error object is a
// failure carrying the provider's message and the whole body.
func (OpenAIAdapter) ParseChatResponse(data map[string]any) valueobjects.AIResponse {
	if msg, ok := errorMessage(data); ok {
		return valueobjects.Failure(msg, data)
	}
	content := dig(data, "choices", 0, "message", "content")
	if content == nil {
		return valueobjects.Failure("No content in AI response.", data)
	}
	usage, _ := data["usage"].(map[string]any)
	return valueobjects.Success(phpString(content), usage, data)
}

// ParseStreamChunk reads a `data: {...}` line's choices[0].delta.content;
// `data: [DONE]` ends the stream.
func (OpenAIAdapter) ParseStreamChunk(line string) (string, bool) {
	payload, ok := strings.CutPrefix(line, "data: ")
	if !ok {
		return "", false
	}
	if payload == "[DONE]" {
		return "", true
	}
	var v map[string]any
	if json.Unmarshal([]byte(payload), &v) != nil || len(v) == 0 {
		return "", false
	}
	delta, _ := dig(v, "choices", 0, "delta", "content").(string)
	return delta, false
}