package js

import (
	"fmt"
	"path/filepath"
	"reflect"
	"sort"
	"strings"

	"apigo.cc/go/jsmod"
)

// Doc generates a comprehensive TypeScript definition (.d.ts) for the Go/JS environment.
func Doc() string {
	var sb strings.Builder
	sb.WriteString("/**\n * Go/JS Low-Code Environment Type Definitions\n")
	sb.WriteString(" * Generated by js.Doc(). DO NOT EDIT.\n */\n\n")

	// 1. Basic Opaque types (Manual fallback for critical non-project types)
	sb.WriteString("/** Opaque handle to Go context.Context */\n")
	sb.WriteString("interface GoContext { _isGoContext: true; }\n")
	sb.WriteString("/** Opaque handle to Go log.Logger */\n")
	sb.WriteString("interface GoLogger { _isGoLogger: true; }\n")
	sb.WriteString("/** Opaque handle to Go net/http.Request */\n")
	sb.WriteString("interface GoHttp_Request { _isGoHttpReq: true; }\n")
	sb.WriteString("/** Opaque handle to Go net/http.Response */\n")
	sb.WriteString("interface GoHttp_Response { _isGoHttpRes: true; }\n")
	sb.WriteString("/** Opaque handle to Go net/url.URL */\n")
	sb.WriteString("interface GoNet_URL { _isGoNetURL: true; }\n\n")

	modules := jsmod.GetModules()
	modNames := make([]string, 0, len(modules))
	for k := range modules {
		modNames = append(modNames, k)
	}
	sort.Strings(modNames)

	ctx := &docCtx{
		seenTypes:  make(map[reflect.Type]string),
		interfaces: make(map[string]string),
		opaqueList: make(map[string]bool),
	}

	// 2. Build Module Interfaces
	moduleDefs := make(map[string]string)
	for _, modName := range modNames {
		mod := modules[modName]
		ctx.currentMod = modName

		var msb strings.Builder
		msb.WriteString(fmt.Sprintf("interface %s_Module {\n", strings.Title(modName)))

		expKeys := make([]string, 0, len(mod.Exports))
		for k := range mod.Exports {
			expKeys = append(expKeys, k)
		}
		sort.Strings(expKeys)

		for _, name := range expKeys {
			isHidden := strings.HasPrefix(name, "__export")
			val := mod.Exports[name]

			memberDef := formatExport(name, val, ctx, false)

			if !isHidden {
				isUnsafe := mod.UnsafeList[name]
				if isUnsafe {
					msb.WriteString("  /** @unsafe */\n")
				}
				msb.WriteString(fmt.Sprintf("  %s\n", memberDef))
			}
		}
		msb.WriteString("}")
		moduleDefs[modName] = msb.String()
	}

	// 2. Output Opaque Interfaces (Dynamic)
	opaqueNames := make([]string, 0, len(ctx.opaqueList))
	for name := range ctx.opaqueList {
		opaqueNames = append(opaqueNames, name)
	}
	sort.Strings(opaqueNames)
	for _, name := range opaqueNames {
		sb.WriteString(fmt.Sprintf("interface %s { _is%s: true; }\n", name, name))
	}
	sb.WriteString("\n")

	// 3. Supporting Interfaces
	if len(ctx.interfaces) > 0 {
		sb.WriteString("// --- Supporting Interfaces ---\n\n")
		ifaceNames := make([]string, 0, len(ctx.interfaces))
		for name := range ctx.interfaces {
			ifaceNames = append(ifaceNames, name)
		}
		sort.Strings(ifaceNames)
		for _, name := range ifaceNames {
			sb.WriteString(ctx.interfaces[name])
			sb.WriteString("\n\n")
		}
	}

	// 4. Module Interfaces
	sb.WriteString("// --- Module Definitions ---\n\n")
	for _, modName := range modNames {
		sb.WriteString(moduleDefs[modName])
		sb.WriteString("\n\n")
	}

	// 5. Global 'go' declaration
	sb.WriteString("/** Global entry point for Go bridged modules */\n")
	sb.WriteString("declare const go: {\n")
	for _, modName := range modNames {
		sb.WriteString(fmt.Sprintf("  readonly %s: %s_Module;\n", modName, strings.Title(modName)))
	}
	sb.WriteString("};\n")

	return sb.String()
}

type docCtx struct {
	currentMod string
	seenTypes  map[reflect.Type]string
	interfaces map[string]string
	opaqueList map[string]bool
}

func formatExport(name string, val any, ctx *docCtx, isMethod bool) string {
	t := reflect.TypeOf(val)
	if t == nil {
		return fmt.Sprintf("%s: any;", name)
	}

	if t.Kind() == reflect.Func {
		return fmt.Sprintf("%s%s;", name, formatFunc(t, ctx, isMethod))
	}

	return fmt.Sprintf("%s: %s;", name, goTypeToTS(t, ctx))
}

func formatFunc(t reflect.Type, ctx *docCtx, isMethod bool) string {
	var params []string
	numIn := t.NumIn()
	jsArgIdx := 0

	startIdx := 0
	if isMethod {
		startIdx = 1 // Skip receiver
	}

	isVariadic := t.IsVariadic()

	for i := startIdx; i < numIn; i++ {
		argType := t.In(i)
		typeName := argType.String()
		if typeName == "context.Context" || strings.Contains(typeName, "log.Logger") {
			continue
		}

		isLast := i == numIn-1
		paramName := fmt.Sprintf("arg%d", jsArgIdx)

		if isVariadic && isLast {
			// Variadic parameters are optional in TS
			params = append(params, fmt.Sprintf("...%s: %s", paramName, goTypeToTS(argType.Elem(), ctx)))
		} else if argType.Kind() == reflect.Ptr {
			// Pointer parameters at the end are optional
			params = append(params, fmt.Sprintf("%s?: %s", paramName, goTypeToTS(argType, ctx)))
		} else {
			params = append(params, fmt.Sprintf("%s: %s", paramName, goTypeToTS(argType, ctx)))
		}
		jsArgIdx++
	}

	numOut := t.NumOut()
	var retType string
	if numOut == 0 {
		retType = "void"
	} else {
		realOut := numOut
		if numOut > 0 && t.Out(numOut-1).Implements(reflect.TypeOf((*error)(nil)).Elem()) {
			realOut--
		}

		if realOut <= 0 {
			retType = "void"
		} else if realOut == 1 {
			retType = goTypeToTS(t.Out(0), ctx)
		} else {
			retType = "any[]"
		}
	}

	return fmt.Sprintf("(%s): %s", strings.Join(params, ", "), retType)
}

func goTypeToTS(t reflect.Type, ctx *docCtx) string {
	if t == nil {
		return "any"
	}

	for t.Kind() == reflect.Ptr {
		t = t.Elem()
	}

	pkgPath := t.PkgPath()
	rawName := t.Name()

	// 1. Blacklist / Filter
	if isTypeUnusable(t) {
		return "any"
	}

	// 2. Map primitive-like types (even with PkgPath) to TS primitives
	switch t.Kind() {
	case reflect.String:
		return "string"
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
		reflect.Float32, reflect.Float64:
		// time.Duration is an Int64, but we treat it as number (ms)
		return "number"
	case reflect.Bool:
		return "boolean"
	case reflect.Slice, reflect.Array:
		return goTypeToTS(t.Elem(), ctx) + "[]"
	case reflect.Map:
		// http.Header as a special Record mapping
		if pkgPath == "net/http" && rawName == "Header" {
			return "Record<string, string[]>"
		}
		return fmt.Sprintf("Record<%s, %s>", goTypeToTS(t.Key(), ctx), goTypeToTS(t.Elem(), ctx))
	}

	// 3. Special Mappings for remaining named types (mostly Structs/Interfaces)
	if pkgPath == "time" && rawName == "Time" {
		return registerInterface(t, ctx)
	}

	// 4. Strict Penetration Blocking for named non-project types
	isProject := strings.HasPrefix(pkgPath, "apigo.cc/go/")
	isAnonymous := rawName == ""

	if pkgPath != "" && !isProject {
		base := filepath.Base(pkgPath)
		opaqueName := "Go" + strings.Title(base) + "_" + rawName
		ctx.opaqueList[opaqueName] = true
		return opaqueName
	}

	// 5. Recursive Struct/Interface Parsing
	switch t.Kind() {
	case reflect.Struct:
		if isAnonymous {
			return "{ [key: string]: any }"
		}
		return registerInterface(t, ctx)
	case reflect.Interface:
		return "any"
	default:
		return "any"
	}
}

func registerInterface(t reflect.Type, ctx *docCtx) string {
	if name, ok := ctx.seenTypes[t]; ok {
		return name
	}

	rawName := t.Name()
	pkgPath := t.PkgPath()

	var name string
	if strings.HasPrefix(pkgPath, "apigo.cc/go/") {
		parts := strings.Split(pkgPath, "/")
		name = fmt.Sprintf("%s_%s", strings.Title(parts[len(parts)-1]), rawName)
	} else if pkgPath != "" {
		// Standard lib types like time.Time
		base := filepath.Base(pkgPath)
		name = fmt.Sprintf("Go%s_%s", strings.Title(base), rawName)
	} else {
		name = fmt.Sprintf("%s_%s", strings.Title(ctx.currentMod), rawName)
	}

	ctx.seenTypes[t] = name

	var sb strings.Builder
	sb.WriteString(fmt.Sprintf("interface %s {\n", name))

	// Fields with Tag check
	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		if field.PkgPath != "" || field.Tag.Get("js") == "-" {
			continue
		}
		sb.WriteString(fmt.Sprintf("  %s: %s;\n", field.Name, goTypeToTS(field.Type, ctx)))
	}

	// Methods check
	ptrType := reflect.PtrTo(t)
	methods := make(map[string]reflect.Method)
	for i := 0; i < t.NumMethod(); i++ {
		m := t.Method(i)
		methods[m.Name] = m
	}
	for i := 0; i < ptrType.NumMethod(); i++ {
		m := ptrType.Method(i)
		methods[m.Name] = m
	}

	mNames := make([]string, 0, len(methods))
	for n := range methods {
		mNames = append(mNames, n)
	}
	sort.Strings(mNames)

	for _, n := range mNames {
		m := methods[n]
		if m.PkgPath != "" {
			continue
		}
		if isMethodUnusable(m.Type) {
			continue
		}
		sb.WriteString(fmt.Sprintf("  %s%s;\n", n, formatFunc(m.Type, ctx, true)))
	}

	sb.WriteString("}")
	ctx.interfaces[name] = sb.String()

	return name
}

func isMethodUnusable(t reflect.Type) bool {
	for i := 0; i < t.NumIn(); i++ {
		if isTypeUnusable(t.In(i)) {
			return true
		}
	}
	for i := 0; i < t.NumOut(); i++ {
		if isTypeUnusable(t.Out(i)) {
			return true
		}
	}
	return false
}

func isTypeUnusable(t reflect.Type) bool {
	for t.Kind() == reflect.Ptr || t.Kind() == reflect.Slice {
		t = t.Elem()
	}
	pkgPath := t.PkgPath()
	rawName := t.Name()

	if pkgPath == "reflect" || pkgPath == "runtime" || pkgPath == "unsafe" || pkgPath == "sync" {
		return true
	}
	if pkgPath == "io" && (rawName == "Reader" || rawName == "Writer" || rawName == "Closer") {
		return true
	}
	return false
}