// Package google implements the go-llm v2 provider interface for Google (Gemini).
package google

import (
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"

	"gitea.stevedudenhoeffer.com/steve/go-llm/v2/provider"

	"google.golang.org/genai"
)

// Provider implements the provider.Provider interface for Google Gemini.
type Provider struct {
	apiKey string
}

// New creates a new Google provider.
func New(apiKey string) *Provider {
	return &Provider{apiKey: apiKey}
}

// Complete performs a non-streaming completion.
func (p *Provider) Complete(ctx context.Context, req provider.Request) (provider.Response, error) {
	cl, err := genai.NewClient(ctx, &genai.ClientConfig{
		APIKey:  p.apiKey,
		Backend: genai.BackendGeminiAPI,
	})
	if err != nil {
		return provider.Response{}, fmt.Errorf("google client error: %w", err)
	}

	contents, cfg := p.buildRequest(req)

	resp, err := cl.Models.GenerateContent(ctx, req.Model, contents, cfg)
	if err != nil {
		return provider.Response{}, fmt.Errorf("google completion error: %w", err)
	}

	return p.convertResponse(resp)
}

// Stream performs a streaming completion.
func (p *Provider) Stream(ctx context.Context, req provider.Request, events chan<- provider.StreamEvent) error {
	cl, err := genai.NewClient(ctx, &genai.ClientConfig{
		APIKey:  p.apiKey,
		Backend: genai.BackendGeminiAPI,
	})
	if err != nil {
		return fmt.Errorf("google client error: %w", err)
	}

	contents, cfg := p.buildRequest(req)

	var fullText strings.Builder
	var toolCalls []provider.ToolCall

	for resp, err := range cl.Models.GenerateContentStream(ctx, req.Model, contents, cfg) {
		if err != nil {
			return fmt.Errorf("google stream error: %w", err)
		}

		for _, c := range resp.Candidates {
			if c.Content == nil {
				continue
			}
			for _, part := range c.Content.Parts {
				if part.Text != "" {
					fullText.WriteString(part.Text)
					events <- provider.StreamEvent{
						Type: provider.StreamEventText,
						Text: part.Text,
					}
				}
				if part.FunctionCall != nil {
					args, _ := json.Marshal(part.FunctionCall.Args)
					tc := provider.ToolCall{
						ID:        part.FunctionCall.Name,
						Name:      part.FunctionCall.Name,
						Arguments: string(args),
					}
					toolCalls = append(toolCalls, tc)
					events <- provider.StreamEvent{
						Type:      provider.StreamEventToolStart,
						ToolCall:  &tc,
						ToolIndex: len(toolCalls) - 1,
					}
					events <- provider.StreamEvent{
						Type:      provider.StreamEventToolEnd,
						ToolCall:  &tc,
						ToolIndex: len(toolCalls) - 1,
					}
				}
			}
		}
	}

	events <- provider.StreamEvent{
		Type: provider.StreamEventDone,
		Response: &provider.Response{
			Text:      fullText.String(),
			ToolCalls: toolCalls,
		},
	}

	return nil
}

func (p *Provider) buildRequest(req provider.Request) ([]*genai.Content, *genai.GenerateContentConfig) {
	var contents []*genai.Content
	cfg := &genai.GenerateContentConfig{}

	for _, tool := range req.Tools {
		cfg.Tools = append(cfg.Tools, &genai.Tool{
			FunctionDeclarations: []*genai.FunctionDeclaration{
				{
					Name:        tool.Name,
					Description: tool.Description,
					Parameters:  schemaToGenai(tool.Schema),
				},
			},
		})
	}

	if req.Temperature != nil {
		f := float32(*req.Temperature)
		cfg.Temperature = &f
	}

	if req.MaxTokens != nil {
		cfg.MaxOutputTokens = int32(*req.MaxTokens)
	}

	if req.TopP != nil {
		f := float32(*req.TopP)
		cfg.TopP = &f
	}

	if len(req.Stop) > 0 {
		cfg.StopSequences = req.Stop
	}

	for _, msg := range req.Messages {
		var role genai.Role
		switch msg.Role {
		case "system":
			cfg.SystemInstruction = genai.NewContentFromText(msg.Content, genai.RoleUser)
			continue
		case "assistant":
			role = genai.RoleModel
		case "tool":
			// Tool results go as function responses (Genai uses RoleUser for function responses)
			contents = append(contents, &genai.Content{
				Role: genai.RoleUser,
				Parts: []*genai.Part{
					{
						FunctionResponse: &genai.FunctionResponse{
							Name: msg.ToolCallID,
							Response: map[string]any{
								"result": msg.Content,
							},
						},
					},
				},
			})
			continue
		default:
			role = genai.RoleUser
		}

		var parts []*genai.Part

		if msg.Content != "" {
			parts = append(parts, genai.NewPartFromText(msg.Content))
		}

		// Handle tool calls in assistant messages
		for _, tc := range msg.ToolCalls {
			var args map[string]any
			if tc.Arguments != "" {
				_ = json.Unmarshal([]byte(tc.Arguments), &args)
			}
			parts = append(parts, &genai.Part{
				FunctionCall: &genai.FunctionCall{
					Name: tc.Name,
					Args: args,
				},
			})
		}

		for _, img := range msg.Images {
			if img.URL != "" {
				// Gemini doesn't support URLs directly; download
				resp, err := http.Get(img.URL)
				if err != nil {
					continue
				}
				data, err := io.ReadAll(resp.Body)
				resp.Body.Close()
				if err != nil {
					continue
				}

				mimeType := http.DetectContentType(data)
				parts = append(parts, genai.NewPartFromBytes(data, mimeType))
			} else if img.Base64 != "" {
				data, err := base64.StdEncoding.DecodeString(img.Base64)
				if err != nil {
					continue
				}
				parts = append(parts, genai.NewPartFromBytes(data, img.ContentType))
			}
		}

		contents = append(contents, genai.NewContentFromParts(parts, role))
	}

	return contents, cfg
}

func (p *Provider) convertResponse(resp *genai.GenerateContentResponse) (provider.Response, error) {
	var res provider.Response

	for _, c := range resp.Candidates {
		if c.Content == nil {
			continue
		}
		for _, part := range c.Content.Parts {
			if part.Text != "" {
				res.Text += part.Text
			}
			if part.FunctionCall != nil {
				args, _ := json.Marshal(part.FunctionCall.Args)
				res.ToolCalls = append(res.ToolCalls, provider.ToolCall{
					ID:        part.FunctionCall.Name,
					Name:      part.FunctionCall.Name,
					Arguments: string(args),
				})
			}
		}
	}

	if resp.UsageMetadata != nil {
		res.Usage = &provider.Usage{
			InputTokens:  int(resp.UsageMetadata.PromptTokenCount),
			OutputTokens: int(resp.UsageMetadata.CandidatesTokenCount),
			TotalTokens:  int(resp.UsageMetadata.TotalTokenCount),
		}
	}

	return res, nil
}

// schemaToGenai converts a JSON Schema map to a genai.Schema.
func schemaToGenai(s map[string]any) *genai.Schema {
	if s == nil {
		return nil
	}

	schema := &genai.Schema{}

	if t, ok := s["type"].(string); ok {
		switch t {
		case "object":
			schema.Type = genai.TypeObject
		case "array":
			schema.Type = genai.TypeArray
		case "string":
			schema.Type = genai.TypeString
		case "integer":
			schema.Type = genai.TypeInteger
		case "number":
			schema.Type = genai.TypeNumber
		case "boolean":
			schema.Type = genai.TypeBoolean
		}
	}

	if desc, ok := s["description"].(string); ok {
		schema.Description = desc
	}

	if props, ok := s["properties"].(map[string]any); ok {
		schema.Properties = make(map[string]*genai.Schema)
		for k, v := range props {
			if vm, ok := v.(map[string]any); ok {
				schema.Properties[k] = schemaToGenai(vm)
			}
		}
	}

	if req, ok := s["required"].([]string); ok {
		schema.Required = req
	} else if req, ok := s["required"].([]any); ok {
		for _, r := range req {
			if rs, ok := r.(string); ok {
				schema.Required = append(schema.Required, rs)
			}
		}
	}

	if items, ok := s["items"].(map[string]any); ok {
		schema.Items = schemaToGenai(items)
	}

	if enums, ok := s["enum"].([]string); ok {
		schema.Enum = enums
	} else if enums, ok := s["enum"].([]any); ok {
		for _, e := range enums {
			if es, ok := e.(string); ok {
				schema.Enum = append(schema.Enum, es)
			}
		}
	}

	return schema
}