package transform

import (
	"fmt"
	"regexp"
	"strings"
)

// Go type definitions to inject
const goTypeDefinitions = `
// WriteKit SDK Types
type Post struct {
	Slug        string   ` + "`json:\"slug\"`" + `
	Title       string   ` + "`json:\"title\"`" + `
	Url         string   ` + "`json:\"url\"`" + `
	Excerpt     string   ` + "`json:\"excerpt\"`" + `
	PublishedAt string   ` + "`json:\"publishedAt\"`" + `
	UpdatedAt   string   ` + "`json:\"updatedAt\"`" + `
	Tags        []string ` + "`json:\"tags\"`" + `
	ReadingTime int      ` + "`json:\"readingTime\"`" + `
}

type Author struct {
	Name   string ` + "`json:\"name\"`" + `
	Email  string ` + "`json:\"email\"`" + `
	Avatar string ` + "`json:\"avatar\"`" + `
}

type Blog struct {
	Name string ` + "`json:\"name\"`" + `
	Url  string ` + "`json:\"url\"`" + `
}

type Comment struct {
	Id          string ` + "`json:\"id\"`" + `
	Content     string ` + "`json:\"content\"`" + `
	AuthorName  string ` + "`json:\"authorName\"`" + `
	AuthorEmail string ` + "`json:\"authorEmail\"`" + `
	PostSlug    string ` + "`json:\"postSlug\"`" + `
	ParentId    string ` + "`json:\"parentId\"`" + `
	CreatedAt   string ` + "`json:\"createdAt\"`" + `
}

type Member struct {
	Email        string ` + "`json:\"email\"`" + `
	Name         string ` + "`json:\"name\"`" + `
	SubscribedAt string ` + "`json:\"subscribedAt\"`" + `
}

type Tier struct {
	Name  string ` + "`json:\"name\"`" + `
	Price int    ` + "`json:\"price\"`" + `
}

type TitleChange struct {
	Old string ` + "`json:\"old\"`" + `
	New string ` + "`json:\"new\"`" + `
}

type TagChanges struct {
	Added   []string ` + "`json:\"added\"`" + `
	Removed []string ` + "`json:\"removed\"`" + `
}

type Changes struct {
	Title   TitleChange ` + "`json:\"title\"`" + `
	Content bool        ` + "`json:\"content\"`" + `
	Tags    TagChanges  ` + "`json:\"tags\"`" + `
}

type Period struct {
	Start string ` + "`json:\"start\"`" + `
	End   string ` + "`json:\"end\"`" + `
}

type PageView struct {
	Path  string ` + "`json:\"path\"`" + `
	Views int    ` + "`json:\"views\"`" + `
}

// Event types
type PostPublishedEvent struct {
	Post   Post   ` + "`json:\"post\"`" + `
	Author Author ` + "`json:\"author\"`" + `
	Blog   Blog   ` + "`json:\"blog\"`" + `
}

type PostUpdatedEvent struct {
	Post    Post    ` + "`json:\"post\"`" + `
	Author  Author  ` + "`json:\"author\"`" + `
	Changes Changes ` + "`json:\"changes\"`" + `
}

type CommentCreatedEvent struct {
	Comment Comment ` + "`json:\"comment\"`" + `
	Post    Post    ` + "`json:\"post\"`" + `
}

type CommentInput struct {
	Content     string ` + "`json:\"content\"`" + `
	AuthorName  string ` + "`json:\"authorName\"`" + `
	AuthorEmail string ` + "`json:\"authorEmail\"`" + `
	PostSlug    string ` + "`json:\"postSlug\"`" + `
}

type ValidationResult struct {
	Allowed bool   ` + "`json:\"allowed\"`" + `
	Reason  string ` + "`json:\"reason,omitempty\"`" + `
}

type MemberSubscribedEvent struct {
	Member Member ` + "`json:\"member\"`" + `
	Tier   Tier   ` + "`json:\"tier\"`" + `
}

type ContentRenderInput struct {
	Html string ` + "`json:\"html\"`" + `
	Post Post   ` + "`json:\"post\"`" + `
}

type ContentRenderOutput struct {
	Html string ` + "`json:\"html\"`" + `
}

type AssetUploadedEvent struct {
	Id          string ` + "`json:\"id\"`" + `
	Url         string ` + "`json:\"url\"`" + `
	ContentType string ` + "`json:\"contentType\"`" + `
	Size        int    ` + "`json:\"size\"`" + `
	Width       int    ` + "`json:\"width\"`" + `
	Height      int    ` + "`json:\"height\"`" + `
}

type AnalyticsSyncEvent struct {
	Period    Period     ` + "`json:\"period\"`" + `
	Pageviews int        ` + "`json:\"pageviews\"`" + `
	Visitors  int        ` + "`json:\"visitors\"`" + `
	TopPages  []PageView ` + "`json:\"topPages\"`" + `
}

// Runner SDK wrapper
type runnerSDK struct{}
var Runner = runnerSDK{}

func (r runnerSDK) Log(msg string) {
	pdk.Log(pdk.LogInfo, msg)
}

type httpResponse struct {
	Status  int
	Headers map[string]string
	Body    string
}

func (r runnerSDK) HttpRequest(url, method string, body []byte) httpResponse {
	req := pdk.NewHTTPRequest(pdk.MethodPost, url)
	if method == "GET" {
		req = pdk.NewHTTPRequest(pdk.MethodGet, url)
	}
	if body != nil {
		req.SetBody(body)
	}
	resp := req.Send()
	return httpResponse{
		Status: int(resp.Status()),
		Body:   string(resp.Body()),
	}
}

// Secrets accessor (populated at runtime via pdk.GetConfig)
type secretsAccessor struct{}
var Secrets = secretsAccessor{}
`

// Go transforms plugin source code from the clean API to the Extism-compatible format.
//
// Input (clean API):
//
//	func OnPostPublished(event PostPublishedEvent) error {
//	  Runner.Log("Post published: " + event.Post.Title)
//	  return nil
//	}
//
// Output (Extism-compatible):
//
//	//export on_post_published
//	func onPostPublished() int32 {
//	  var event PostPublishedEvent
//	  if err := pdk.InputJSON(&event); err != nil {
//	    pdk.Log(pdk.LogError, err.Error())
//	    return 1
//	  }
//	  Runner.Log("Post published: " + event.Post.Title)
//	  return 0
//	}
func Go(source string) (string, error) {
	result := source

	// Transform Runner.Secrets.X to pdk.GetConfig("X") calls
	result = transformRunnerSecrets(result)

	// Map of hook functions: CleanName -> export_name
	hookMap := map[string]string{
		"OnPostPublished":   "on_post_published",
		"OnPostUpdated":     "on_post_updated",
		"OnCommentCreated":  "on_comment_created",
		"OnMemberSubscribed": "on_member_subscribed",
		"OnAssetUploaded":   "on_asset_uploaded",
		"OnAnalyticsSync":   "on_analytics_sync",
		"ValidateComment":   "validate_comment",
		"RenderContent":     "render_content",
	}

	// Find all hook functions
	// Pattern: func FuncName(params) returnType {
	funcPattern := regexp.MustCompile(`(?m)^func\s+(\w+)\s*\(([^)]*)\)\s*(\([^)]*\)|[\w\*]+)?\s*\{`)
	matches := funcPattern.FindAllStringSubmatchIndex(result, -1)

	// Process matches in reverse order to preserve indices
	for i := len(matches) - 1; i >= 0; i-- {
		match := matches[i]
		funcName := result[match[2]:match[3]]

		// Check if this is a hook function
		exportName, isHook := hookMap[funcName]
		if !isHook {
			continue
		}

		params := result[match[4]:match[5]]

		// Get return type if present
		returnType := ""
		if match[6] != -1 && match[7] != -1 {
			returnType = strings.TrimSpace(result[match[6]:match[7]])
		}

		// Find the closing brace
		braceStart := match[7]
		if braceStart == -1 {
			braceStart = match[5] + 1
		}
		// Find the actual opening brace position
		for braceStart < len(result) && result[braceStart] != '{' {
			braceStart++
		}
		braceEnd := findClosingBrace(result, braceStart+1)
		if braceEnd == -1 {
			continue
		}

		// Extract function body
		body := result[braceStart+1 : braceEnd]

		// Parse parameters
		eventParam, eventType, secretsParam, secretsType := parseGoParams(params)

		// Build transformed function
		var transformed strings.Builder

		// Add export directive
		transformed.WriteString(fmt.Sprintf("//export %s\n", exportName))

		// New function signature (lowercase name, no params, returns int32)
		lowercaseName := strings.ToLower(funcName[:1]) + funcName[1:]
		transformed.WriteString(fmt.Sprintf("func %s() int32 {\n", lowercaseName))

		// Inject event deserialization if we have an event parameter
		if eventParam != "" && eventType != "" {
			transformed.WriteString(fmt.Sprintf("  var %s %s\n", eventParam, eventType))
			transformed.WriteString(fmt.Sprintf("  if err := pdk.InputJSON(&%s); err != nil {\n", eventParam))
			transformed.WriteString("    pdk.Log(pdk.LogError, err.Error())\n")
			transformed.WriteString("    return 1\n")
			transformed.WriteString("  }\n")
		}

		// Inject secrets if present
		if secretsParam != "" && secretsType != "" {
			secretsCode := generateGoSecretsInjection(source, secretsParam, secretsType)
			transformed.WriteString(secretsCode)
		}

		// Transform the body
		transformedBody := body

		// Check if return type includes a result type (tuple return)
		hasResultReturn := strings.Contains(returnType, ",") || (returnType != "" && returnType != "error" && !strings.HasPrefix(returnType, "("))

		if hasResultReturn {
			// Transform returns that have result values
			transformedBody = transformGoReturnsWithResult(body)
		} else {
			// Transform simple error returns to int32 returns
			transformedBody = transformGoReturns(body)
		}

		transformed.WriteString(transformedBody)

		// Ensure we have a return 0 at the end
		if !strings.HasSuffix(strings.TrimSpace(transformedBody), "return 0") {
			transformed.WriteString("\n  return 0\n")
		}

		transformed.WriteString("}")

		// Replace the original function
		result = result[:match[0]] + transformed.String() + result[braceEnd+1:]
	}

	// Inject imports and type definitions
	result = injectGoImportsAndTypes(result)

	return result, nil
}

// transformRunnerSecrets transforms Runner.Secrets.X to pdk.GetConfig("X") calls
func transformRunnerSecrets(source string) string {
	// Transform Runner.Secrets.SomeName to func() string { v, _ := pdk.GetConfig("SOME_NAME"); return v }()
	pattern := regexp.MustCompile(`Runner\.Secrets\.(\w+)`)
	return pattern.ReplaceAllStringFunc(source, func(match string) string {
		m := pattern.FindStringSubmatch(match)
		if m != nil {
			fieldName := m[1]
			configKey := toUpperSnakeCase(fieldName)
			return fmt.Sprintf(`func() string { v, _ := pdk.GetConfig("%s"); return v }()`, configKey)
		}
		return match
	})
}

// injectGoImportsAndTypes injects the necessary imports and type definitions
func injectGoImportsAndTypes(source string) string {
	// Check if source already has package main
	if !strings.Contains(source, "package main") {
		source = "package main\n\n" + source
	}

	// Replace "package main" with package + imports + types
	importBlock := `package main

import (
	"github.com/extism/go-pdk"
)
` + goTypeDefinitions

	// Remove the original package line and add our block
	result := regexp.MustCompile(`package\s+main\s*\n*`).ReplaceAllString(source, "")
	return importBlock + "\n" + result
}

// parseGoParams extracts parameters from Go function signature
func parseGoParams(params string) (eventParam, eventType, secretsParam, secretsType string) {
	params = strings.TrimSpace(params)
	if params == "" {
		return
	}

	// Split by comma (handling potential spaces)
	parts := splitGoParams(params)

	// First parameter is the event
	if len(parts) >= 1 {
		eventPart := strings.TrimSpace(parts[0])
		// Match: paramName ParamType
		re := regexp.MustCompile(`(\w+)\s+(\w+)`)
		if m := re.FindStringSubmatch(eventPart); m != nil {
			eventParam = m[1]
			eventType = m[2]
		}
	}

	// Second parameter (if present) is secrets
	if len(parts) >= 2 {
		secretsPart := strings.TrimSpace(parts[1])
		re := regexp.MustCompile(`(\w+)\s+(\w+)`)
		if m := re.FindStringSubmatch(secretsPart); m != nil {
			secretsParam = m[1]
			secretsType = m[2]
		}
	}

	return
}

// splitGoParams splits Go parameters, handling edge cases
func splitGoParams(params string) []string {
	var parts []string
	var current strings.Builder
	depth := 0

	for _, ch := range params {
		switch ch {
		case '(':
			depth++
			current.WriteRune(ch)
		case ')':
			depth--
			current.WriteRune(ch)
		case ',':
			if depth == 0 {
				parts = append(parts, current.String())
				current.Reset()
			} else {
				current.WriteRune(ch)
			}
		default:
			current.WriteRune(ch)
		}
	}
	if current.Len() > 0 {
		parts = append(parts, current.String())
	}

	return parts
}

// generateGoSecretsInjection creates code to build the secrets struct from pdk.GetConfig() calls
func generateGoSecretsInjection(source, secretsParam, secretsType string) string {
	// Find the struct definition for the secrets type
	structPattern := regexp.MustCompile(fmt.Sprintf(`(?s)type\s+%s\s+struct\s*\{([^}]*)\}`, regexp.QuoteMeta(secretsType)))
	match := structPattern.FindStringSubmatch(source)
	if match == nil {
		return fmt.Sprintf("  var %s %s\n", secretsParam, secretsType)
	}

	// Parse struct body for field names
	structBody := match[1]
	fieldPattern := regexp.MustCompile(`(\w+)\s+string`)
	fields := fieldPattern.FindAllStringSubmatch(structBody, -1)

	if len(fields) == 0 {
		return fmt.Sprintf("  var %s %s\n", secretsParam, secretsType)
	}

	// Build the secrets struct initialization
	var builder strings.Builder
	builder.WriteString(fmt.Sprintf("  %s := %s{\n", secretsParam, secretsType))
	for _, field := range fields {
		fieldName := field[1]
		// Convert Go field name to config key (e.g., SlackWebhook -> SLACK_WEBHOOK)
		configKey := toUpperSnakeCase(fieldName)
		builder.WriteString(fmt.Sprintf("    %s: func() string { v, _ := pdk.GetConfig(\"%s\"); return v }(),\n", fieldName, configKey))
	}
	builder.WriteString("  }\n")

	return builder.String()
}

// toUpperSnakeCase converts CamelCase to UPPER_SNAKE_CASE
func toUpperSnakeCase(s string) string {
	var result strings.Builder
	for i, ch := range s {
		if i > 0 && ch >= 'A' && ch <= 'Z' {
			result.WriteRune('_')
		}
		result.WriteRune(ch)
	}
	return strings.ToUpper(result.String())
}

// transformGoReturns transforms return statements from error returns to int32 returns
func transformGoReturns(body string) string {
	// Replace "return nil" with "return 0"
	result := regexp.MustCompile(`return\s+nil\b`).ReplaceAllString(body, "return 0")

	// Replace "return err" or "return someErr" with error handling
	result = regexp.MustCompile(`return\s+(\w+)\s*$`).ReplaceAllStringFunc(result, func(match string) string {
		re := regexp.MustCompile(`return\s+(\w+)`)
		m := re.FindStringSubmatch(match)
		if m != nil && m[1] != "nil" && m[1] != "0" && m[1] != "1" {
			// It's an error variable
			return fmt.Sprintf("if %s != nil { pdk.Log(pdk.LogError, %s.Error()); return 1 }; return 0", m[1], m[1])
		}
		return match
	})

	return result
}

// transformGoReturnsWithResult transforms returns that have a result value
func transformGoReturnsWithResult(body string) string {
	// Match: return result, nil or return result, err
	returnPattern := regexp.MustCompile(`return\s+(\w+),\s*(\w+)\s*$`)

	return returnPattern.ReplaceAllStringFunc(body, func(match string) string {
		m := returnPattern.FindStringSubmatch(match)
		if m != nil {
			result := m[1]
			errVar := m[2]
			if errVar == "nil" {
				return fmt.Sprintf("pdk.OutputJSON(%s); return 0", result)
			}
			return fmt.Sprintf("if %s != nil { pdk.Log(pdk.LogError, %s.Error()); return 1 }; pdk.OutputJSON(%s); return 0", errVar, errVar, result)
		}
		return match
	})
}