package gethwrappers

import (
	"bytes"
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/token"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/ethereum/go-ethereum/accounts/abi"
	gethParams "github.com/ethereum/go-ethereum/params"
	"golang.org/x/tools/go/ast/astutil"

	"github.com/smartcontractkit/chainlink/v2/core/chains/evm/utils"
)

const headerComment = `// Code generated - DO NOT EDIT.
// This file is a generated binding and any manual changes will be lost.

`

// AbigenArgs is the arguments to the abigen executable. E.g., Bin is the -bin
// arg.
type AbigenArgs struct {
	Bin, ABI, Out, Type, Pkg string
}

// Abigen calls Abigen  with the given arguments
//
// It might seem like a shame, to shell out to another golang program like
// this, but the abigen executable is the stable public interface to the
// geth contract-wrapper machinery.
//
// Check whether native abigen is installed, and has correct version
func Abigen(a AbigenArgs) {
	var versionResponse bytes.Buffer
	abigenExecutablePath := filepath.Join(GetProjectRoot(), "tools/bin/abigen")
	abigenVersionCheck := exec.Command(abigenExecutablePath, "--version")
	abigenVersionCheck.Stdout = &versionResponse
	if err := abigenVersionCheck.Run(); err != nil {
		Exit("no native abigen; you must install it (`make abigen` in the "+
			"chainlink root dir)", err)
	}
	version := string(regexp.MustCompile(`[0-9]+\.[0-9]+\.[0-9]+`).Find(
		versionResponse.Bytes()))
	if version != gethParams.Version {
		Exit(fmt.Sprintf("wrong version (%s) of abigen; install the correct one "+
			"(%s) with `make abigen` in the chainlink root dir", version,
			gethParams.Version),
			nil)
	}
	args := []string{
		"-abi", a.ABI,
		"-out", a.Out,
		"-type", a.Type,
		"-pkg", a.Pkg,
	}
	if a.Bin != "-" {
		args = append(args, "-bin", a.Bin)
	}
	buildCommand := exec.Command(abigenExecutablePath, args...)
	var buildResponse bytes.Buffer
	buildCommand.Stderr = &buildResponse
	if err := buildCommand.Run(); err != nil {
		Exit("failure while building "+a.Pkg+" wrapper, stderr: "+buildResponse.String(), err)
	}

	ImproveAbigenOutput(a.Out, a.ABI)
}

func ImproveAbigenOutput(path string, abiPath string) {
	abiBytes, err := os.ReadFile(abiPath)
	if err != nil {
		Exit("Error while improving abigen output", err)
	}
	abi, err := abi.JSON(strings.NewReader(string(abiBytes)))
	if err != nil {
		Exit("Error while improving abigen output", err)
	}

	bs, err := os.ReadFile(path)
	if err != nil {
		Exit("Error while improving abigen output", err)
	}

	fset, fileNode := parseFile(bs)
	logNames := getLogNames(fileNode)
	if len(logNames) > 0 {
		astutil.AddImport(fset, fileNode, "fmt")
		astutil.AddImport(fset, fileNode, "github.com/smartcontractkit/chainlink/v2/core/gethwrappers/generated")
	}
	contractName := getContractName(fileNode)
	fileNode = addContractStructFields(contractName, fileNode)
	fileNode = replaceAnonymousStructs(contractName, fileNode)
	bs = generateCode(fset, fileNode)
	bs = writeAdditionalMethods(contractName, logNames, abi, bs)
	err = os.WriteFile(path, bs, 0600)
	if err != nil {
		Exit("Error while writing improved abigen source", err)
	}

	fset, fileNode = parseFile(bs)
	fileNode = writeInterface(contractName, fileNode)
	bs = generateCode(fset, fileNode)
	bs = addHeader(bs)

	err = os.WriteFile(path, bs, 0600)
	if err != nil {
		Exit("Error while writing improved abigen source", err)
	}
}

func parseFile(bs []byte) (*token.FileSet, *ast.File) {
	fset := token.NewFileSet()
	fileNode, err := parser.ParseFile(fset, "", string(bs), parser.AllErrors)
	if err != nil {
		Exit("Error while improving abigen output", err)
	}
	return fset, fileNode
}

func generateCode(fset *token.FileSet, fileNode *ast.File) []byte {
	var buf bytes.Buffer
	err := format.Node(&buf, fset, fileNode)
	if err != nil {
		Exit("Error while writing improved abigen source", err)
	}
	return buf.Bytes()
}

func getContractName(fileNode *ast.File) string {
	// Search for the ABI const e.g. VRFCoordinatorV2ABI = "0x..."
	var contractName string
	astutil.Apply(fileNode, func(cursor *astutil.Cursor) bool {
		x, is := cursor.Node().(*ast.ValueSpec)
		if !is {
			return true
		}
		if len(x.Names) > 0 {
			for _, n := range x.Names {
				if len(n.Name) < 3 {
					return true
				}
				if n.Name[len(n.Name)-3:] != "ABI" {
					return true
				}
				contractName = n.Name[:len(n.Name)-3]
			}
		}
		return false
	}, nil)
	return contractName
}

// Add the `.address` and `.abi` fields to the contract struct.
func addContractStructFields(contractName string, fileNode *ast.File) *ast.File {
	fileNode = addContractStructFieldsToStruct(contractName, fileNode)
	fileNode = addContractStructFieldsToConstructor(contractName, fileNode)
	fileNode = addContractStructFieldsToDeployMethod(contractName, fileNode)
	return fileNode
}

// Add the fields to the contract struct.
func addContractStructFieldsToStruct(contractName string, fileNode *ast.File) *ast.File {
	return astutil.Apply(fileNode, func(cursor *astutil.Cursor) bool {
		x, is := cursor.Node().(*ast.StructType)
		if !is {
			return true
		}
		theType, is := cursor.Parent().(*ast.TypeSpec)
		if !is {
			return false
		} else if theType.Name.Name != contractName {
			return false
		}

		addrField := &ast.Field{
			Names: []*ast.Ident{ast.NewIdent("address")},
			Type: &ast.SelectorExpr{
				X:   ast.NewIdent("common"),
				Sel: ast.NewIdent("Address"),
			},
		}

		abiField := &ast.Field{
			Names: []*ast.Ident{ast.NewIdent("abi")},
			Type: &ast.SelectorExpr{
				X:   ast.NewIdent("abi"),
				Sel: ast.NewIdent("ABI"),
			},
		}
		x.Fields.List = append([]*ast.Field{addrField, abiField}, x.Fields.List...)
		return false
	}, nil).(*ast.File)
}

// Add the fields to the return value of the constructor.
func addContractStructFieldsToConstructor(contractName string, fileNode *ast.File) *ast.File {
	return astutil.Apply(fileNode, func(cursor *astutil.Cursor) bool {
		x, is := cursor.Node().(*ast.FuncDecl)
		if !is {
			return true
		} else if x.Name.Name != "New"+contractName {
			return false
		}

		for _, stmt := range x.Body.List {
			returnStmt, is := stmt.(*ast.ReturnStmt)
			if !is {
				continue
			}
			lit, is := returnStmt.Results[0].(*ast.UnaryExpr).X.(*ast.CompositeLit)
			if !is {
				continue
			}
			addressExpr := &ast.KeyValueExpr{
				Key:   ast.NewIdent("address"),
				Value: ast.NewIdent("address"),
			}
			abiExpr := &ast.KeyValueExpr{
				Key:   ast.NewIdent("abi"),
				Value: ast.NewIdent("abi"),
			}
			lit.Elts = append([]ast.Expr{addressExpr, abiExpr}, lit.Elts...)
		}

		parseABIStmt := &ast.AssignStmt{
			Lhs: []ast.Expr{ast.NewIdent("abi"), ast.NewIdent("err")},
			Tok: token.DEFINE,
			Rhs: []ast.Expr{
				&ast.CallExpr{
					Fun: &ast.SelectorExpr{
						X:   ast.NewIdent("abi"),
						Sel: ast.NewIdent("JSON"),
					},
					Args: []ast.Expr{
						&ast.CallExpr{
							Fun: &ast.SelectorExpr{
								X:   ast.NewIdent("strings"),
								Sel: ast.NewIdent("NewReader"),
							},
							Args: []ast.Expr{ast.NewIdent(contractName + "ABI")},
						},
					},
				},
			},
		}
		checkParseABIErrStmt := &ast.IfStmt{
			Cond: &ast.BinaryExpr{
				X:  ast.NewIdent("err"),
				Op: token.NEQ,
				Y:  ast.NewIdent("nil"),
			},
			Body: &ast.BlockStmt{
				List: []ast.Stmt{
					&ast.ReturnStmt{
						Results: []ast.Expr{ast.NewIdent("nil"), ast.NewIdent("err")},
					},
				},
			},
		}

		x.Body.List = append([]ast.Stmt{parseABIStmt, checkParseABIErrStmt}, x.Body.List...)
		return false
	}, nil).(*ast.File)
}

// Add the fields to the returned struct in the 'Deploy<contractName>' method.
func addContractStructFieldsToDeployMethod(contractName string, fileNode *ast.File) *ast.File {
	return astutil.Apply(fileNode, func(cursor *astutil.Cursor) bool {
		x, is := cursor.Node().(*ast.FuncDecl)
		if !is {
			return true
		} else if x.Name.Name != "Deploy"+contractName {
			return false
		}

		for _, stmt := range x.Body.List {
			returnStmt, is := stmt.(*ast.ReturnStmt)
			if !is {
				continue
			}
			if len(returnStmt.Results) < 3 {
				continue
			}
			rs, is := returnStmt.Results[2].(*ast.UnaryExpr)
			if !is {
				return true
			}
			lit, is := rs.X.(*ast.CompositeLit)
			if !is {
				continue
			}
			addressExpr := &ast.KeyValueExpr{
				Key:   ast.NewIdent("address"),
				Value: ast.NewIdent("address"),
			}
			abiExpr := &ast.KeyValueExpr{
				Key:   ast.NewIdent("abi"),
				Value: ast.NewIdent("*parsed"),
			}
			lit.Elts = append([]ast.Expr{addressExpr, abiExpr}, lit.Elts...)
		}
		return false
	}, nil).(*ast.File)
}

func getLogNames(fileNode *ast.File) []string {
	var logNames []string
	astutil.Apply(fileNode, func(cursor *astutil.Cursor) bool {
		x, is := cursor.Node().(*ast.FuncDecl)
		if !is {
			return true
		} else if !strings.HasPrefix(x.Name.Name, "Parse") {
			return false
		}
		logNames = append(logNames, x.Name.Name[len("Parse"):])
		return false
	}, nil)
	return logNames
}

func replaceAnonymousStructs(contractName string, fileNode *ast.File) *ast.File {
	done := map[string]bool{}
	return astutil.Apply(fileNode, func(cursor *astutil.Cursor) bool {
		// Replace all anonymous structs with named structs
		x, is := cursor.Node().(*ast.FuncDecl)
		if !is {
			return true
		} else if len(x.Type.Results.List) == 0 {
			return false
		}
		theStruct, is := x.Type.Results.List[0].Type.(*ast.StructType)
		if !is {
			return false
		}

		methodName := x.Name.Name
		x.Type.Results.List[0].Type = ast.NewIdent(methodName)

		x.Body = astutil.Apply(x.Body, func(cursor *astutil.Cursor) bool {
			if _, is := cursor.Node().(*ast.StructType); !is {
				return true
			}
			if call, is := cursor.Parent().(*ast.CallExpr); is {
				for i, arg := range call.Args {
					if arg == cursor.Node() {
						call.Args[i] = ast.NewIdent(methodName)
						break
					}
				}
			}
			return true
		}, nil).(*ast.BlockStmt)

		if done[contractName+methodName] {
			return true
		}

		// Add the named structs to the bottom of the file
		fileNode.Decls = append(fileNode.Decls, &ast.GenDecl{
			Tok: token.TYPE,
			Specs: []ast.Spec{
				&ast.TypeSpec{
					Name: ast.NewIdent(methodName),
					Type: theStruct,
				},
			},
		})

		done[contractName+methodName] = true
		return false
	}, nil).(*ast.File)
}

func writeAdditionalMethods(contractName string, logNames []string, abi abi.ABI, bs []byte) []byte {
	// Write the ParseLog method
	if len(logNames) > 0 {
		var logSwitchBody string
		for _, logName := range logNames {
			logSwitchBody += fmt.Sprintf(`case _%v.abi.Events["%v"].ID:
        return _%v.Parse%v(log)
`, contractName, logName, contractName, logName)
		}

		bs = append(bs, []byte(fmt.Sprintf(`
func (_%v *%v) ParseLog(log types.Log) (generated.AbigenLog, error) {
    switch log.Topics[0] {
    %v
    default:
        return nil, fmt.Errorf("abigen wrapper received unknown log topic: %%v", log.Topics[0])
    }
}
`, contractName, contractName, logSwitchBody))...)
	}

	// Write the Topic method
	for _, logName := range logNames {
		bs = append(bs, []byte(fmt.Sprintf(`
func (%v%v) Topic() common.Hash {
    return common.HexToHash("%v")
}
`, contractName, logName, abi.Events[logName].ID.Hex()))...)
	}

	// Write the Address method to the bottom of the file
	bs = append(bs, []byte(fmt.Sprintf(`
func (_%v *%v) Address() common.Address {
    return _%v.address
}
`, contractName, contractName, contractName))...)

	return bs
}

func writeInterface(contractName string, fileNode *ast.File) *ast.File {
	// Generate an interface for the contract
	var methods []*ast.Field
	ast.Inspect(fileNode, func(n ast.Node) bool {
		switch x := n.(type) {
		case *ast.FuncDecl:
			if x.Recv == nil {
				return true
			}
			star, is := x.Recv.List[0].Type.(*ast.StarExpr)
			if !is {
				return false
			}

			typeName := star.X.(*ast.Ident).String()
			if typeName != contractName && typeName != contractName+"Caller" && typeName != contractName+"Transactor" && typeName != contractName+"Filterer" {
				return true
			}

			methods = append(methods, &ast.Field{
				Names: []*ast.Ident{x.Name},
				Type:  x.Type,
			})
		}
		return true
	})

	fileNode.Decls = append(fileNode.Decls, &ast.GenDecl{
		Tok: token.TYPE,
		Specs: []ast.Spec{
			&ast.TypeSpec{
				Name: ast.NewIdent(contractName + "Interface"),
				Type: &ast.InterfaceType{
					Methods: &ast.FieldList{
						List: methods,
					},
				},
			},
		},
	})

	return fileNode
}

func addHeader(code []byte) []byte {
	return utils.ConcatBytes([]byte(headerComment), code)
}