package responses

import (
	"bytes"
	"crypto/rand"
	"math/big"
	"strings"

	"github.com/tidwall/gjson"
	"github.com/tidwall/sjson"
)

// ConvertOpenAIResponsesRequestToClaude transforms an OpenAI Responses API request
// into a Claude Messages API request using only gjson/sjson for JSON handling.
// It supports:
// - instructions -> system message
// - input[].type==message with input_text/output_text -> user/assistant messages
// - function_call -> assistant tool_use
// - function_call_output -> user tool_result
// - tools[].parameters -> tools[].input_schema
// - max_output_tokens -> max_tokens
// - stream passthrough via parameter
func ConvertOpenAIResponsesRequestToClaude(modelName string, inputRawJSON []byte, stream bool) []byte {
	rawJSON := bytes.Clone(inputRawJSON)

	// Base Claude message payload
	out := `{"model":"","max_tokens":32000,"messages":[]}`

	root := gjson.ParseBytes(rawJSON)

	if v := root.Get("reasoning.effort"); v.Exists() {
		out, _ = sjson.Set(out, "thinking.type", "enabled")

		switch v.String() {
		case "none":
			out, _ = sjson.Set(out, "thinking.type", "disabled")
		case "minimal":
			out, _ = sjson.Set(out, "thinking.budget_tokens", 1024)
		case "low":
			out, _ = sjson.Set(out, "thinking.budget_tokens", 4096)
		case "medium":
			out, _ = sjson.Set(out, "thinking.budget_tokens", 8192)
		case "high":
			out, _ = sjson.Set(out, "thinking.budget_tokens", 24576)
		}
	}

	// Helper for generating tool call IDs when missing
	genToolCallID := func() string {
		const letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
		var b strings.Builder
		for i := 0; i < 24; i++ {
			n, _ := rand.Int(rand.Reader, big.NewInt(int64(len(letters))))
			b.WriteByte(letters[n.Int64()])
		}
		return "toolu_" + b.String()
	}

	// Model
	out, _ = sjson.Set(out, "model", modelName)

	// Max tokens
	if mot := root.Get("max_output_tokens"); mot.Exists() {
		out, _ = sjson.Set(out, "max_tokens", mot.Int())
	}

	// Stream
	out, _ = sjson.Set(out, "stream", stream)

	// instructions -> as a leading message (use role user for Claude API compatibility)
	if instr := root.Get("instructions"); instr.Exists() && instr.Type == gjson.String && instr.String() != "" {
		sysMsg := `{"role":"user","content":""}`
		sysMsg, _ = sjson.Set(sysMsg, "content", instr.String())
		out, _ = sjson.SetRaw(out, "messages.-1", sysMsg)
	}

	// input array processing
	if input := root.Get("input"); input.Exists() && input.IsArray() {
		input.ForEach(func(_, item gjson.Result) bool {
			typ := item.Get("type").String()
			switch typ {
			case "message":
				// Determine role from content type (input_text=user, output_text=assistant)
				var role string
				var text strings.Builder
				if parts := item.Get("content"); parts.Exists() && parts.IsArray() {
					parts.ForEach(func(_, part gjson.Result) bool {
						ptype := part.Get("type").String()
						if ptype == "input_text" || ptype == "output_text" {
							if t := part.Get("text"); t.Exists() {
								text.WriteString(t.String())
							}
							if ptype == "input_text" {
								role = "user"
							} else if ptype == "output_text" {
								role = "assistant"
							}
						}
						return true
					})
				}

				// Fallback to given role if content types not decisive
				if role == "" {
					r := item.Get("role").String()
					switch r {
					case "user", "assistant", "system":
						role = r
					default:
						role = "user"
					}
				}

				if text.Len() > 0 || role == "system" {
					msg := `{"role":"","content":""}`
					msg, _ = sjson.Set(msg, "role", role)
					if text.Len() > 0 {
						msg, _ = sjson.Set(msg, "content", text.String())
					} else {
						msg, _ = sjson.Set(msg, "content", "")
					}
					out, _ = sjson.SetRaw(out, "messages.-1", msg)
				}

			case "function_call":
				// Map to assistant tool_use
				callID := item.Get("call_id").String()
				if callID == "" {
					callID = genToolCallID()
				}
				name := item.Get("name").String()
				argsStr := item.Get("arguments").String()

				toolUse := `{"type":"tool_use","id":"","name":"","input":{}}`
				toolUse, _ = sjson.Set(toolUse, "id", callID)
				toolUse, _ = sjson.Set(toolUse, "name", name)
				if argsStr != "" && gjson.Valid(argsStr) {
					toolUse, _ = sjson.SetRaw(toolUse, "input", argsStr)
				}

				asst := `{"role":"assistant","content":[]}`
				asst, _ = sjson.SetRaw(asst, "content.-1", toolUse)
				out, _ = sjson.SetRaw(out, "messages.-1", asst)

			case "function_call_output":
				// Map to user tool_result
				callID := item.Get("call_id").String()
				outputStr := item.Get("output").String()
				toolResult := `{"type":"tool_result","tool_use_id":"","content":""}`
				toolResult, _ = sjson.Set(toolResult, "tool_use_id", callID)
				toolResult, _ = sjson.Set(toolResult, "content", outputStr)

				usr := `{"role":"user","content":[]}`
				usr, _ = sjson.SetRaw(usr, "content.-1", toolResult)
				out, _ = sjson.SetRaw(out, "messages.-1", usr)
			}
			return true
		})
	}

	// tools mapping: parameters -> input_schema
	if tools := root.Get("tools"); tools.Exists() && tools.IsArray() {
		toolsJSON := "[]"
		tools.ForEach(func(_, tool gjson.Result) bool {
			tJSON := `{"name":"","description":"","input_schema":{}}`
			if n := tool.Get("name"); n.Exists() {
				tJSON, _ = sjson.Set(tJSON, "name", n.String())
			}
			if d := tool.Get("description"); d.Exists() {
				tJSON, _ = sjson.Set(tJSON, "description", d.String())
			}

			if params := tool.Get("parameters"); params.Exists() {
				tJSON, _ = sjson.SetRaw(tJSON, "input_schema", params.Raw)
			} else if params = tool.Get("parametersJsonSchema"); params.Exists() {
				tJSON, _ = sjson.SetRaw(tJSON, "input_schema", params.Raw)
			}

			toolsJSON, _ = sjson.SetRaw(toolsJSON, "-1", tJSON)
			return true
		})
		if gjson.Parse(toolsJSON).IsArray() && len(gjson.Parse(toolsJSON).Array()) > 0 {
			out, _ = sjson.SetRaw(out, "tools", toolsJSON)
		}
	}

	// Map tool_choice similar to Chat Completions translator (optional in docs, safe to handle)
	if toolChoice := root.Get("tool_choice"); toolChoice.Exists() {
		switch toolChoice.Type {
		case gjson.String:
			switch toolChoice.String() {
			case "auto":
				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{"type": "auto"})
			case "none":
				// Leave unset; implies no tools
			case "required":
				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{"type": "any"})
			}
		case gjson.JSON:
			if toolChoice.Get("type").String() == "function" {
				fn := toolChoice.Get("function.name").String()
				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{"type": "tool", "name": fn})
			}
		default:

		}
	}

	return []byte(out)
}