package main

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/anthropics/anthropic-sdk-go"
	"github.com/anthropics/anthropic-sdk-go/packages/param"
)

// ErrModelNotFound is returned when the configured Anthropic model is no longer available
// (deprecated or removed). Callers can use errors.Is to detect this and surface an
// actionable message to admins/owners while keeping the response vague for regular users.
var ErrModelNotFound = errors.New("model not found or deprecated")

// getAnthropicResponse streams the model's response. Each completed text block
// is delivered to onSegment as soon as the model finishes writing it — so the
// caller can send segments to Telegram with natural rhythm around tool calls,
// rather than batched at the very end of the turn. onSegment may be nil for
// callers that only want the joined text (voice TTS, sticker reactions, etc.).
// The returned string is every text segment joined by blank lines.
func (b *Bot) getAnthropicResponse(ctx context.Context, messages []anthropic.BetaMessageParam, isNewChat, isOwner, isEmojiOnly bool, username string, firstName string, lastName string, isPremium bool, languageCode string, messageTime int, onSegment func(string) error) (string, error) {
	// Use prompts from config
	var systemMessage string
	if isNewChat {
		systemMessage = b.config.SystemPrompts["new_chat"]
	} else {
		systemMessage = b.config.SystemPrompts["continue_conversation"]
	}

	// Combine default prompt with custom instructions
	systemMessage = b.config.SystemPrompts["default"] + " " + b.config.SystemPrompts["custom_instructions"] + " " + systemMessage

	// Handle username placeholder
	usernameValue := username
	if username == "" {
		usernameValue = "unknown" // Use "unknown" when username is not available
	}
	systemMessage = strings.ReplaceAll(systemMessage, "{username}", usernameValue)

	// Handle firstname placeholder
	firstnameValue := firstName
	if firstName == "" {
		firstnameValue = "unknown" // Use "unknown" when first name is not available
	}
	systemMessage = strings.ReplaceAll(systemMessage, "{firstname}", firstnameValue)

	// Handle lastname placeholder
	lastnameValue := lastName
	if lastName == "" {
		lastnameValue = "" // Empty string when last name is not available
	}
	systemMessage = strings.ReplaceAll(systemMessage, "{lastname}", lastnameValue)

	// Handle language code placeholder
	langValue := languageCode
	if languageCode == "" {
		langValue = "en" // Default to English when language code is not available
	}
	systemMessage = strings.ReplaceAll(systemMessage, "{language}", langValue)

	// Handle premium status
	premiumStatus := "regular user"
	if isPremium {
		premiumStatus = "premium user"
	}
	systemMessage = strings.ReplaceAll(systemMessage, "{premium_status}", premiumStatus)

	// Handle time awareness
	timeObj := time.Unix(int64(messageTime), 0)
	hour := timeObj.Hour()
	var timeContext string
	if hour >= 5 && hour < 12 {
		timeContext = "morning"
	} else if hour >= 12 && hour < 18 {
		timeContext = "afternoon"
	} else if hour >= 18 && hour < 22 {
		timeContext = "evening"
	} else {
		timeContext = "night"
	}
	systemMessage = strings.ReplaceAll(systemMessage, "{time_context}", timeContext)

	if !isOwner {
		systemMessage += " " + b.config.SystemPrompts["avoid_sensitive"]
	}

	if isEmojiOnly {
		systemMessage += " " + b.config.SystemPrompts["respond_with_emojis"]
	}

	// Debug logging
	InfoLogger.Printf("Sending %d messages to Anthropic", len(messages))

	params := anthropic.BetaMessageNewParams{
		Model:     b.config.Model,
		MaxTokens: 1000,
		Messages:  messages,
		System:    []anthropic.BetaTextBlockParam{{Text: systemMessage}},
	}

	// Apply temperature if set in config
	if b.config.Temperature != nil {
		params.Temperature = param.NewOpt(float64(*b.config.Temperature))
	}

	// MCP servers + matching toolset entries. The mcp-client-2025-11-20 beta
	// requires per-tool filtering on the toolset (Configs + DefaultConfig),
	// NOT the deprecated per-server tool_configuration block.
	if len(b.config.MCPServers) > 0 {
		mcpServers := make([]anthropic.BetaRequestMCPServerURLDefinitionParam, 0, len(b.config.MCPServers))
		tools := make([]anthropic.BetaToolUnionParam, 0, len(b.config.MCPServers))
		for _, s := range b.config.MCPServers {
			srv := anthropic.BetaRequestMCPServerURLDefinitionParam{
				Name: s.Name,
				URL:  s.URL,
			}
			if s.AuthorizationToken != "" {
				srv.AuthorizationToken = param.NewOpt(s.AuthorizationToken)
			}
			mcpServers = append(mcpServers, srv)

			toolset := &anthropic.BetaMCPToolsetParam{
				MCPServerName: s.Name,
			}
			if len(s.AllowedTools) > 0 {
				toolset.DefaultConfig = anthropic.BetaMCPToolDefaultConfigParam{
					Enabled: param.NewOpt(false),
				}
				toolset.Configs = make(map[string]anthropic.BetaMCPToolConfigParam, len(s.AllowedTools))
				for _, tool := range s.AllowedTools {
					toolset.Configs[tool] = anthropic.BetaMCPToolConfigParam{
						Enabled: param.NewOpt(true),
					}
				}
			}
			tools = append(tools, anthropic.BetaToolUnionParam{OfMCPToolset: toolset})
		}
		params.MCPServers = mcpServers
		params.Tools = tools
		params.Betas = []anthropic.AnthropicBeta{anthropic.AnthropicBetaMCPClient2025_11_20}
	}

	stream := b.anthropicClient.Beta.Messages.NewStreaming(ctx, params)
	defer func() {
		if err := stream.Close(); err != nil {
			ErrorLogger.Printf("[stream] close failed: %v", err)
		}
	}()

	// Per-block accumulators. Reset on content_block_start, consumed on
	// content_block_stop. Only one block is active at a time per the SSE
	// contract; SDK guarantees deltas arrive between matching start/stop.
	var (
		allSegments     []string
		currentKind     string
		currentText     strings.Builder
		currentInputJSON strings.Builder
		currentTUseName, currentTUseServer, currentTUseID string
		currentTResultUseID, currentTResultServer         string
		currentTResultIsError                             bool
		currentTResultContent                             string
	)

	for stream.Next() {
		e := stream.Current()
		switch e.Type {
		case "content_block_start":
			cbs := e.AsContentBlockStart()
			currentKind = cbs.ContentBlock.Type
			currentText.Reset()
			currentInputJSON.Reset()
			switch currentKind {
			case "mcp_tool_use":
				currentTUseName = cbs.ContentBlock.Name
				currentTUseServer = cbs.ContentBlock.ServerName
				currentTUseID = cbs.ContentBlock.ID
			case "mcp_tool_result":
				currentTResultUseID = cbs.ContentBlock.ToolUseID
				currentTResultServer = cbs.ContentBlock.ServerName
				currentTResultIsError = cbs.ContentBlock.IsError
				// Tool-result content arrives populated on start (server-side
				// pre-assembled), not via subsequent deltas like text/JSON.
				currentTResultContent = cbs.ContentBlock.JSON.Content.Raw()
			}

		case "content_block_delta":
			cbd := e.AsContentBlockDelta()
			switch cbd.Delta.Type {
			case "text_delta":
				if currentKind == "text" {
					currentText.WriteString(cbd.Delta.Text)
				}
			case "input_json_delta":
				if currentKind == "mcp_tool_use" {
					currentInputJSON.WriteString(cbd.Delta.PartialJSON)
				}
			}

		case "content_block_stop":
			switch currentKind {
			case "text":
				seg := strings.TrimSpace(currentText.String())
				if seg != "" {
					allSegments = append(allSegments, seg)
					if onSegment != nil {
						if cbErr := onSegment(seg); cbErr != nil {
							// Log but keep streaming — the model's response
							// is still inbound; we want it recorded even if
							// one Telegram send failed.
							ErrorLogger.Printf("[stream] onSegment failed: %v", cbErr)
						}
					}
				}
			case "mcp_tool_use":
				InfoLogger.Printf("[mcp] tool_use server=%q name=%q id=%q input=%s",
					currentTUseServer, currentTUseName, currentTUseID, currentInputJSON.String())
			case "mcp_tool_result":
				preview := currentTResultContent
				if len(preview) > 500 {
					preview = preview[:500] + "...(truncated)"
				}
				InfoLogger.Printf("[mcp] tool_result tool_use_id=%q server=%q is_error=%v content=%s",
					currentTResultUseID, currentTResultServer, currentTResultIsError, preview)
			default:
				if currentKind != "" {
					InfoLogger.Printf("[mcp] block type=%q (unhandled)", currentKind)
				}
			}
			currentKind = ""
		}
	}

	if err := stream.Err(); err != nil {
		var apiErr *anthropic.Error
		if errors.As(err, &apiErr) && apiErr.StatusCode == http.StatusNotFound {
			return "", fmt.Errorf("%w: %s", ErrModelNotFound, b.config.Model)
		}
		return "", fmt.Errorf("error creating Anthropic message: %w", err)
	}

	if len(allSegments) == 0 {
		return "", fmt.Errorf("unexpected response format from Anthropic")
	}
	return strings.Join(allSegments, "\n\n"), nil
}