package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"strings"
)

type ModelsResponse struct {
	Object string  `json:"object"`
	Data   []Model `json:"data"`
}

type Model struct {
	ID       string                 `json:"id"`
	Object   string                 `json:"object"`
	Created  int64                  `json:"created,omitempty"`
	OwnedBy  string                 `json:"owned_by,omitempty"`
	Metadata map[string]interface{} `json:"metadata,omitempty"`
}

type Limit struct {
	Context int `json:"context"`
	Output  int `json:"output"`
}

type OpencodeModel struct {
	Name  string `json:"name"`
	Limit Limit  `json:"limit"`
}

// V2-native shape: "provider" / "npm" / "options"
type DynamicProviderV2 struct {
	Npm       string                   `json:"npm"`
	Name      string                   `json:"name"`
	Options   map[string]string        `json:"options"`
	Models    map[string]OpencodeModel `json:"models,omitempty"`
}

// V1-compatible shape: "providers" / "package" / "settings"
type DynamicProviderV1 struct {
	Package  string                   `json:"package"`
	Name     string                   `json:"name"`
	Settings map[string]string        `json:"settings"`
	Models   map[string]OpencodeModel `json:"models,omitempty"`
}

// OpencodeConfigV2 is the V2-native top-level shape
type OpencodeConfigV2 struct {
	Schema   string                      `json:"$schema"`
	Provider map[string]DynamicProviderV2 `json:"provider"`
}

// OpencodeConfigV1 is the V1-compatible top-level shape
type OpencodeConfigV1 struct {
	Schema    string                       `json:"$schema"`
	Providers map[string]DynamicProviderV1 `json:"providers"`
}

const (
	formatV2Native = "v2" // default
	formatV1Compat = "v1"
)

func getIntFromMetadata(md map[string]interface{}, key string, defaultVal int) int {
	if md == nil {
		return defaultVal
	}
	if v, ok := md[key]; ok {
		if i, ok := v.(float64); ok {
			return int(i)
		}
	}
	return defaultVal
}

func buildConfig(providerName, baseURL, token string, format string, data []Model) ([]byte, error) {
	schema := "https://opencode.ai/config.json"

	switch format {
	case formatV2Native:
		return buildV2Config(schema, providerName, baseURL, token, data)
	case formatV1Compat:
		return buildV1Config(schema, providerName, baseURL, token, data)
	default:
		return nil, fmt.Errorf("unsupported format: %s", format)
	}
}

func buildV2Config(schema, providerName, baseURL, token string, data []Model) ([]byte, error) {
	provider := DynamicProviderV2{
		Npm:   "@ai-sdk/openai-compatible",
		Name:  providerName,
		Options: map[string]string{
			"baseURL": baseURL,
			"apiKey":  token,
		},
		Models: make(map[string]OpencodeModel, len(data)),
	}

	for _, m := range data {
		ctx := getIntFromMetadata(m.Metadata, "context_window", 131072)
		out := getIntFromMetadata(m.Metadata, "max_output_tokens", 8192)
		provider.Models[m.ID] = OpencodeModel{
			Name: m.ID,
			Limit: Limit{
				Context: ctx,
				Output:  out,
			},
		}
	}

	config := OpencodeConfigV2{
		Schema:   schema,
		Provider: map[string]DynamicProviderV2{providerName: provider},
	}

	return json.MarshalIndent(config, "", "  ")
}

func buildV1Config(schema, providerName, baseURL, token string, data []Model) ([]byte, error) {
	provider := DynamicProviderV1{
		Package:  "@ai-sdk/openai-compatible",
		Name:     providerName,
		Settings: map[string]string{"baseURL": baseURL, "apiKey": token},
		Models:   make(map[string]OpencodeModel, len(data)),
	}

	for _, m := range data {
		ctx := getIntFromMetadata(m.Metadata, "context_window", 131072)
		out := getIntFromMetadata(m.Metadata, "max_output_tokens", 8192)
		provider.Models[m.ID] = OpencodeModel{
			Name: m.ID,
			Limit: Limit{
				Context: ctx,
				Output:  out,
			},
		}
	}

	config := OpencodeConfigV1{
		Schema:    schema,
		Providers: map[string]DynamicProviderV1{providerName: provider},
	}

	return json.MarshalIndent(config, "", "  ")
}

func main() {
	var providerName, baseURL, apiURL, outputFile, token, format string

	flag.StringVar(&providerName, "provider", "Myprovider", "Name of the provider (default: Myprovider)")
	flag.StringVar(&baseURL, "baseurl", "", "Base URL for the provider (required, e.g., http://localhost:8080/v1)")
	flag.StringVar(&apiURL, "apiurl", "", "API URL to fetch models from (default: <baseurl>/models)")
	flag.StringVar(&token, "token", "", "API token sent as Authorization: Bearer and x-api-key (optional)")
	flag.StringVar(&outputFile, "output", "opencode.jsonc", "Output file name (default: opencode.jsonc)")
	flag.StringVar(&format, "format", formatV2Native, "Output format: v2 (default, V2-native: provider/npm/options) or v1 (V1-compatible: providers/package/settings)")

	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: %s [options]\n\n", os.Args[0])
		fmt.Fprintf(os.Stderr, "Examples:\n")
		fmt.Fprintf(os.Stderr, "  %s --provider Myprovider --baseurl http://localhost:8080/v1\n", os.Args[0])
		fmt.Fprintf(os.Stderr, "  %s --provider OmniRoute --baseurl http://localhost:20128/v1 --format v1\n\n", os.Args[0])
		flag.PrintDefaults()
	}

	flag.Parse()

	if baseURL == "" {
		log.Fatal("--baseurl is required")
	}

	if apiURL == "" {
		apiURL = strings.TrimSuffix(baseURL, "/") + "/models"
	}

	// Validate format
	switch format {
	case formatV2Native, formatV1Compat:
	default:
		log.Fatalf("Invalid --format %q: must be %q or %q", format, formatV2Native, formatV1Compat)
	}

	req, err := http.NewRequest("GET", apiURL, nil)
	if err != nil {
		log.Fatalf("Failed to create request: %v", err)
	}
	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
		req.Header.Set("x-api-key", token)
	}
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		log.Fatalf("Failed to fetch %s: %v", apiURL, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		log.Fatalf("Unexpected status code: %d", resp.StatusCode)
	}

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Fatalf("Failed to read response: %v", err)
	}

	var modelsResp ModelsResponse
	if err := json.Unmarshal(body, &modelsResp); err != nil {
		log.Fatalf("Failed to parse models response: %v", err)
	}

	out, err := buildConfig(providerName, baseURL, token, format, modelsResp.Data)
	if err != nil {
		log.Fatalf("Failed to build config: %v", err)
	}

	if err := os.WriteFile(outputFile, out, 0644); err != nil {
		log.Fatalf("Failed to write %s: %v", outputFile, err)
	}

	fmt.Printf("Successfully wrote %s with %d models for provider %s (format: %s)\n",
		outputFile, len(modelsResp.Data), providerName, format)
}