package binding

import (
	"bytes"
	"fmt"
	"go/format"
	"go/token"
	"io"
	"sort"
	"strconv"
	"strings"
	"text/template"
	"unicode"

	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
	"github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest"
	"github.com/nspcc-dev/neo-go/pkg/util"
)

const srcTmpl = `
{{- define "METHOD" -}}
// {{.Name}} {{.Comment}}
func {{.Name}}({{range $index, $arg := .Arguments -}}
	{{- if ne $index 0}}, {{end}}
		{{- .Name}} {{.Type}}
	{{- end}}) {{if .ReturnType }}{{ .ReturnType }} {
	return neogointernal.CallWithToken(Hash, "{{ .NameABI }}", int(contract.{{ .CallFlag }})
		{{- range $arg := .Arguments -}}, {{.Name}}{{end}}).({{ .ReturnType }})
	{{- else -}} {
	neogointernal.CallWithTokenNoRet(Hash, "{{ .NameABI }}", int(contract.{{ .CallFlag }})
		{{- range $arg := .Arguments -}}, {{.Name}}{{end}})
	{{- end}}
}
{{- end -}}
// Package {{.PackageName}} contains wrappers for {{.ContractName}} contract.
package {{.PackageName}}

import (
{{range $m := .Imports}}	"{{ $m }}"
{{end}})

// Hash contains contract hash in big-endian form.
const Hash = "{{ .Hash }}"
{{range $m := .Methods}}
{{template "METHOD" $m }}
{{end}}`

type (
	// Config contains parameter for the generated binding.
	Config struct {
		Package  string             `yaml:"package,omitempty"`
		Manifest *manifest.Manifest `yaml:"-"`
		// Hash denotes the contract hash and is allowed to be empty for RPC bindings
		// generation (if not provided by the user).
		Hash      util.Uint160                 `yaml:"hash,omitempty"`
		Overrides map[string]Override          `yaml:"overrides,omitempty"`
		CallFlags map[string]callflag.CallFlag `yaml:"callflags,omitempty"`
		// NamedTypes contains exported structured types that have some name (even
		// if the original structure doesn't) and a number of internal fields. The
		// map key is in the form of `namespace.name`, the value is fully-qualified
		// and possibly nested description of the type structure.
		NamedTypes map[string]ExtendedType `yaml:"namedtypes,omitempty"`
		// Types contains type structure description for various types used in
		// smartcontract. The map key has one of the following forms:
		// - `methodName` for method return value;
		// - `mathodName.paramName` for method's parameter value.
		// - `eventName.paramName` for event's parameter value.
		Types  map[string]ExtendedType `yaml:"types,omitempty"`
		Output io.Writer               `yaml:"-"`
	}

	ExtendedType struct {
		Base      smartcontract.ParamType `yaml:"base"`
		Name      string                  `yaml:"name,omitempty"`      // Structure name, omitted for arrays, interfaces and maps.
		Interface string                  `yaml:"interface,omitempty"` // Interface type name, "iterator" only for now.
		Key       smartcontract.ParamType `yaml:"key,omitempty"`       // Key type (only simple types can be used for keys) for maps.
		Value     *ExtendedType           `yaml:"value,omitempty"`     // Value type for iterators, arrays and maps.
		Fields    []FieldExtendedType     `yaml:"fields,omitempty"`    // Ordered type data for structure fields.
	}

	FieldExtendedType struct {
		Field        string `yaml:"field"`
		ExtendedType `yaml:",inline"`
	}

	ContractTmpl struct {
		PackageName  string
		ContractName string
		Imports      []string
		Hash         string
		Methods      []MethodTmpl
	}

	MethodTmpl struct {
		Name       string
		NameABI    string
		CallFlag   string
		Comment    string
		Arguments  []ParamTmpl
		ReturnType string
	}

	ParamTmpl struct {
		Name string
		Type string
	}
)

var srcTemplate = template.Must(template.New("generate").Parse(srcTmpl))

// NewConfig initializes and returns a new config instance.
func NewConfig() Config {
	return Config{
		Overrides:  make(map[string]Override),
		CallFlags:  make(map[string]callflag.CallFlag),
		NamedTypes: make(map[string]ExtendedType),
		Types:      make(map[string]ExtendedType),
	}
}

// Generate writes Go file containing smartcontract bindings to the `cfg.Output`.
// It doesn't check manifest from Config for validity, incorrect manifest can
// lead to unexpected results.
func Generate(cfg Config) error {
	ctr := TemplateFromManifest(cfg, scTypeToGo)
	ctr.Imports = append(ctr.Imports, "github.com/nspcc-dev/neo-go/pkg/interop/contract")
	ctr.Imports = append(ctr.Imports, "github.com/nspcc-dev/neo-go/pkg/interop/neogointernal")
	sort.Strings(ctr.Imports)

	return FExecute(srcTemplate, cfg.Output, ctr)
}

// FExecute tries to execute given template over the data provided, apply gofmt
// rules to the result and write the result to the provided io.Writer. If a
// format error occurs while formatting the resulting binding, then the generated
// binding is written "as is" and no error is returned.
func FExecute(tmplt *template.Template, out io.Writer, data any) error {
	in := bytes.NewBuffer(nil)
	err := tmplt.Execute(in, data)
	if err != nil {
		return fmt.Errorf("failed to execute template: %w", err)
	}
	res := in.Bytes()

	fmtRes, err := format.Source(res)
	if err != nil {
		// OK, still write something to the resulting file, our generator has known
		// bugs that make the resulting code uncompilable.
		fmtRes = res
	}
	_, err = out.Write(fmtRes)
	if err != nil {
		return fmt.Errorf("failed to write the resulting binding: %w", err)
	}
	return nil
}

func scTypeToGo(name string, typ smartcontract.ParamType, cfg *Config) (string, string) {
	if over, ok := cfg.Overrides[name]; ok {
		return over.TypeName, over.Package
	}

	switch typ {
	case smartcontract.AnyType:
		return "any", ""
	case smartcontract.BoolType:
		return "bool", ""
	case smartcontract.IntegerType:
		return "int", ""
	case smartcontract.ByteArrayType:
		return "[]byte", ""
	case smartcontract.StringType:
		return "string", ""
	case smartcontract.Hash160Type:
		return "interop.Hash160", "github.com/nspcc-dev/neo-go/pkg/interop"
	case smartcontract.Hash256Type:
		return "interop.Hash256", "github.com/nspcc-dev/neo-go/pkg/interop"
	case smartcontract.PublicKeyType:
		return "interop.PublicKey", "github.com/nspcc-dev/neo-go/pkg/interop"
	case smartcontract.SignatureType:
		return "interop.Signature", "github.com/nspcc-dev/neo-go/pkg/interop"
	case smartcontract.ArrayType:
		return "[]any", ""
	case smartcontract.MapType:
		return "map[string]any", ""
	case smartcontract.InteropInterfaceType:
		return "any", ""
	case smartcontract.VoidType:
		return "", ""
	default:
		panic("unreachable")
	}
}

// TemplateFromManifest create a contract template using the given configuration
// and type conversion function. It assumes manifest to be present in the
// configuration and assumes it to be correct (passing IsValid check).
func TemplateFromManifest(cfg Config, scTypeConverter func(string, smartcontract.ParamType, *Config) (string, string)) ContractTmpl {
	var hStr string
	if !cfg.Hash.Equals(util.Uint160{}) {
		for _, b := range cfg.Hash.BytesBE() {
			hStr += fmt.Sprintf("\\x%02x", b)
		}
	}

	ctr := ContractTmpl{
		PackageName:  cfg.Package,
		ContractName: cfg.Manifest.Name,
		Hash:         hStr,
	}
	if ctr.PackageName == "" {
		buf := bytes.NewBuffer(make([]byte, 0, len(cfg.Manifest.Name)))
		for _, r := range cfg.Manifest.Name {
			if unicode.IsLetter(r) {
				buf.WriteRune(unicode.ToLower(r))
			}
		}

		ctr.PackageName = buf.String()
	}

	imports := make(map[string]struct{})
	seen := make(map[string]bool)
	for _, m := range cfg.Manifest.ABI.Methods {
		seen[m.Name] = false
	}
	for _, m := range cfg.Manifest.ABI.Methods {
		if m.Name[0] == '_' {
			continue
		}

		// Consider `perform(a)` and `perform(a, b)` methods.
		// First, try to export the second method with `Perform2` name.
		// If `perform2` is already in the manifest, use `perform_2` with as many underscores
		// as needed to eliminate name conflicts. It will produce long names in certain circumstances,
		// but if the manifest contains lots of similar names with trailing underscores, delicate naming
		// was probably not the goal.
		name := m.Name
		if v, ok := seen[name]; !ok || v {
			suffix := strconv.Itoa(len(m.Parameters))
			for ; seen[name]; name = m.Name + suffix {
				suffix = "_" + suffix
			}
		}
		seen[name] = true

		mtd := MethodTmpl{
			Name:     upperFirst(name),
			NameABI:  m.Name,
			CallFlag: callflag.All.String(),
			Comment:  fmt.Sprintf("invokes `%s` method of contract.", m.Name),
		}
		if f, ok := cfg.CallFlags[m.Name]; ok {
			mtd.CallFlag = f.String()
		} else if m.Safe {
			mtd.CallFlag = callflag.ReadOnly.String()
		}

		var varnames = make(map[string]bool)
		for i := range m.Parameters {
			name := m.Parameters[i].Name
			typeStr, pkg := scTypeConverter(m.Name+"."+name, m.Parameters[i].Type, &cfg)
			if pkg != "" {
				imports[pkg] = struct{}{}
			}
			if token.IsKeyword(name) {
				name = name + "v"
			}
			for varnames[name] {
				name = name + "_"
			}
			varnames[name] = true
			mtd.Arguments = append(mtd.Arguments, ParamTmpl{
				Name: name,
				Type: typeStr,
			})
		}

		typeStr, pkg := scTypeConverter(m.Name, m.ReturnType, &cfg)
		if pkg != "" {
			imports[pkg] = struct{}{}
		}
		mtd.ReturnType = typeStr
		ctr.Methods = append(ctr.Methods, mtd)
	}

	for imp := range imports {
		ctr.Imports = append(ctr.Imports, imp)
	}

	return ctr
}

func upperFirst(s string) string {
	return strings.ToUpper(s[0:1]) + s[1:]
}

// Equals compares two extended types field-by-field and returns true if they are
// equal.
func (e *ExtendedType) Equals(other *ExtendedType) bool {
	if e == nil && other == nil {
		return true
	}
	if e != nil && other == nil ||
		e == nil && other != nil {
		return false
	}
	if !((e.Base == other.Base || (e.Base == smartcontract.ByteArrayType || e.Base == smartcontract.StringType) &&
		(other.Base == smartcontract.ByteArrayType || other.Base == smartcontract.StringType)) &&
		e.Name == other.Name &&
		e.Interface == other.Interface &&
		e.Key == other.Key) {
		return false
	}
	if len(e.Fields) != len(other.Fields) {
		return false
	}
	for i := range e.Fields {
		if e.Fields[i].Field != other.Fields[i].Field {
			return false
		}
		if !e.Fields[i].ExtendedType.Equals(&other.Fields[i].ExtendedType) {
			return false
		}
	}
	return (e.Value == nil && other.Value == nil) || (e.Value != nil && other.Value != nil && e.Value.Equals(other.Value))
}