package openai

import (
	"encoding/json"
	"errors"
)

// --- Responses API request parsing & conversion ---

// ParseResponsesRequest converts a raw OpenAI Responses API (POST /v1/responses)
// request body into a ChatCompletionRequest suitable for the upstream gateway.
// It translates input→messages, instructions→system message, max_output_tokens→
// max_tokens, and reshapes tools from the Responses flat format to the Chat
// Completions nested {function:{…}} format.
func ParseResponsesRequest(body []byte) (ChatCompletionRequest, error) {
	var raw map[string]json.RawMessage
	if err := json.Unmarshal(body, &raw); err != nil {
		return ChatCompletionRequest{}, err
	}

	var req ChatCompletionRequest
	if v, ok := raw["model"]; ok {
		_ = json.Unmarshal(v, &req.Model)
	}
	if v, ok := raw["stream"]; ok {
		_ = json.Unmarshal(v, &req.Stream)
	}

	// Build messages from instructions + input.
	messages := make([]map[string]any, 0, 4)
	if v, ok := raw["instructions"]; ok {
		var s string
		if json.Unmarshal(v, &s) == nil && s != "" {
			messages = append(messages, map[string]any{"role": "system", "content": s})
		}
	}
	if v, ok := raw["input"]; ok {
		msgs, err := responsesInputToMessages(v)
		if err != nil {
			return req, err
		}
		messages = append(messages, msgs...)
	}
	req.Messages = messages

	// Extra: renamed + pass-through fields sent to upstream as-is.
	extra := map[string]json.RawMessage{}
	if v, ok := raw["max_output_tokens"]; ok {
		extra["max_tokens"] = v
	}
	for _, key := range []string{
		"temperature", "top_p", "top_k", "frequency_penalty",
		"presence_penalty", "stop", "seed", "user",
	} {
		if v, ok := raw[key]; ok {
			extra[key] = v
		}
	}
	if v, ok := raw["tools"]; ok {
		if translated, err := translateResponsesTools(v); err == nil {
			extra["tools"] = translated
		} else {
			extra["tools"] = v // fall back to pass-through
		}
	}
	if v, ok := raw["tool_choice"]; ok {
		extra["tool_choice"] = v
	}
	// Structured Outputs: Responses API uses text.format instead of
	// response_format. Translate text.format → response_format for the
	// upstream Chat Completions endpoint.
	if v, ok := raw["text"]; ok {
		if rf, err := translateTextFormat(v); err == nil {
			extra["response_format"] = rf
		}
	}
	req.Extra = extra
	return req, nil
}

// translateTextFormat converts the Responses API "text" field (containing a
// "format" sub-object) into a Chat Completions response_format value.
//   - {text:{format:{type:"json_object"}}}        → {type:"json_object"}
//   - {text:{format:{type:"json_schema",name,schema,strict}}} →
//     {type:"json_schema",json_schema:{name,schema,strict}}
func translateTextFormat(textRaw json.RawMessage) (json.RawMessage, error) {
	var text struct {
		Format map[string]any `json:"format"`
	}
	if err := json.Unmarshal(textRaw, &text); err != nil {
		return nil, err
	}
	if len(text.Format) == 0 {
		return nil, errors.New("empty text.format")
	}
	t, _ := text.Format["type"].(string)
	switch t {
	case "json_object":
		return json.Marshal(map[string]any{"type": "json_object"})
	case "json_schema":
		js := map[string]any{}
		for _, k := range []string{"name", "schema", "strict"} {
			if v, ok := text.Format[k]; ok {
				js[k] = v
			}
		}
		return json.Marshal(map[string]any{"type": "json_schema", "json_schema": js})
	default:
		return json.Marshal(text.Format) // pass through unknown types
	}
}

// ResponsesMeta holds fields from the Responses API request that should be
// echoed back in the response object (the OpenAI SDK requires them).
type ResponsesMeta struct {
	ParallelToolCalls any
	ToolChoice        any
	Tools             any
	Temperature       any
	TopP              any
	MaxOutputTokens   any
}

// ParseResponsesMeta extracts echo-back fields from the raw request body.
func ParseResponsesMeta(body []byte) ResponsesMeta {
	var m map[string]any
	_ = json.Unmarshal(body, &m)
	meta := ResponsesMeta{
		ParallelToolCalls: false,
		ToolChoice:        "auto",
		Tools:             []any{},
	}
	if v, ok := m["parallel_tool_calls"]; ok {
		meta.ParallelToolCalls = v
	}
	if v, ok := m["tool_choice"]; ok {
		meta.ToolChoice = v
	}
	// Tools are echoed back in the Responses API flat format (not the
	// translated Chat Completions format).
	if v, ok := m["tools"]; ok {
		meta.Tools = v
	} else {
		meta.Tools = []any{}
	}
	if v, ok := m["temperature"]; ok {
		meta.Temperature = v
	}
	if v, ok := m["top_p"]; ok {
		meta.TopP = v
	}
	if v, ok := m["max_output_tokens"]; ok {
		meta.MaxOutputTokens = v
	}
	return meta
}

// responsesInputToMessages converts the Responses API "input" field (which may
// be a plain string or an array of input items) into Chat Completions messages.
func responsesInputToMessages(input json.RawMessage) ([]map[string]any, error) {
	// Case 1: input is a plain string.
	var s string
	if json.Unmarshal(input, &s) == nil {
		return []map[string]any{{"role": "user", "content": s}}, nil
	}

	// Case 2: input is an array of items.
	var items []map[string]json.RawMessage
	if err := json.Unmarshal(input, &items); err != nil {
		return nil, err
	}

	messages := make([]map[string]any, 0, len(items))
	for _, item := range items {
		// Determine the type — most items are message-like with a role.
		var role string
		if v, ok := item["role"]; ok {
			_ = json.Unmarshal(v, &role)
		}
		var itemType string
		if v, ok := item["type"]; ok {
			_ = json.Unmarshal(v, &itemType)
		}

		switch {
		case itemType == "function_call":
			// An assistant tool call from a previous turn.
			msg := map[string]any{"role": "assistant"}
			tc := map[string]any{"type": "function"}
			inner := map[string]any{}
			if v, ok := item["name"]; ok {
				var name string
				_ = json.Unmarshal(v, &name)
				inner["name"] = name
			}
			if v, ok := item["arguments"]; ok {
				var args string
				_ = json.Unmarshal(v, &args)
				inner["arguments"] = args
			}
			if v, ok := item["call_id"]; ok {
				var id string
				_ = json.Unmarshal(v, &id)
				tc["id"] = id
			}
			tc["function"] = inner
			msg["tool_calls"] = []any{tc}
			messages = append(messages, msg)
		case itemType == "function_call_output":
			// A tool result from a previous turn.
			msg := map[string]any{"role": "tool"}
			if v, ok := item["call_id"]; ok {
				var id string
				_ = json.Unmarshal(v, &id)
				msg["tool_call_id"] = id
			}
			if v, ok := item["output"]; ok {
				var out string
				_ = json.Unmarshal(v, &out)
				msg["content"] = out
			}
			messages = append(messages, msg)
		default:
			// Standard message item with role + content.
			if role == "" {
				role = "user"
			}
			// "developer" maps to "system" for broad upstream compatibility.
			if role == "developer" {
				role = "system"
			}
			msg := map[string]any{"role": role}
			if v, ok := item["content"]; ok {
				msg["content"] = convertContentParts(v)
			} else {
				msg["content"] = ""
			}
			messages = append(messages, msg)
		}
	}
	return messages, nil
}

// convertContentParts converts a Responses API content field (string or array
// of content parts) into the Chat Completions content format.
func convertContentParts(raw json.RawMessage) any {
	// Content is a plain string.
	var s string
	if json.Unmarshal(raw, &s) == nil {
		return s
	}
	// Content is an array of parts.
	var parts []map[string]any
	if json.Unmarshal(raw, &parts) != nil {
		return string(raw) // fallback
	}
	result := make([]map[string]any, 0, len(parts))
	for _, p := range parts {
		pt, _ := p["type"].(string)
		switch pt {
		case "input_text", "output_text", "text":
			result = append(result, map[string]any{"type": "text", "text": p["text"]})
		case "input_image":
			img := map[string]any{"type": "image_url"}
			if url, ok := p["image_url"]; ok {
				img["image_url"] = map[string]any{"url": url}
			} else if d, ok := p["image"]; ok {
				img["image_url"] = map[string]any{"url": d}
			}
			result = append(result, img)
		default:
			// Pass through unknown part types as-is.
			result = append(result, p)
		}
	}
	if len(result) == 0 {
		return ""
	}
	return result
}

// translateResponsesTools converts tools from the Responses API flat format
// to the Chat Completions nested {type:"function",function:{…}} format.
func translateResponsesTools(raw json.RawMessage) (json.RawMessage, error) {
	var tools []map[string]any
	if err := json.Unmarshal(raw, &tools); err != nil {
		return nil, err
	}
	out := make([]map[string]any, 0, len(tools))
	for _, t := range tools {
		tt, _ := t["type"].(string)
		if tt != "function" && tt != "" {
			// Non-function tool types (web_search, file_search, etc.) —
			// pass through as-is; upstream may or may not support them.
			out = append(out, t)
			continue
		}
		fn := map[string]any{}
		for _, key := range []string{"name", "description", "parameters", "strict"} {
			if v, ok := t[key]; ok {
				fn[key] = v
			}
		}
		out = append(out, map[string]any{"type": "function", "function": fn})
	}
	return json.Marshal(out)
}

// --- Responses API response building ---

// UsageToResponses converts a Chat Completions usage value (as decoded by
// json.Unmarshal into any) to the Responses API usage field names
// (input_tokens / output_tokens instead of prompt_tokens / completion_tokens).
func UsageToResponses(v any) any {
	if v == nil {
		return nil
	}
	b, err := json.Marshal(v)
	if err != nil {
		return v
	}
	var m map[string]any
	if json.Unmarshal(b, &m) != nil {
		return v
	}
	out := map[string]any{}
	if pt, ok := m["prompt_tokens"]; ok {
		out["input_tokens"] = pt
	}
	if ct, ok := m["completion_tokens"]; ok {
		out["output_tokens"] = ct
	}
	if tt, ok := m["total_tokens"]; ok {
		out["total_tokens"] = tt
	}
	if d, ok := m["prompt_tokens_details"]; ok {
		out["input_tokens_details"] = d
	} else if d, ok := m["input_tokens_details"]; ok {
		out["input_tokens_details"] = d
	}
	if d, ok := m["completion_tokens_details"]; ok {
		out["output_tokens_details"] = d
	} else if d, ok := m["output_tokens_details"]; ok {
		out["output_tokens_details"] = d
	}
	return out
}