package main

import (
	"fmt"
	"log"
	"os"
	"time"

	"github.com/iancoleman/strcase"
	"golang.org/x/sys/execabs"
)

// ErrorSpec specifies the error we care about.
type ErrorSpec struct {
	// Errno is the error name as an errno value (e.g., ECONNREFUSED).
	Errno string

	// Failure is the error name according to OONI (e.g., FailureConnectionRefused).
	Failure string
}

// Specs contains all the error specs.
var Specs = []ErrorSpec{{
	Errno:   "ECANCELED",
	Failure: "OperationCanceled",
}, {
	Errno:   "ECONNREFUSED",
	Failure: "ConnectionRefused",
}, {
	Errno:   "ECONNRESET",
	Failure: "ConnectionReset",
}, {
	Errno:   "EHOSTUNREACH",
	Failure: "HostUnreachable",
}, {
	Errno:   "ETIMEDOUT",
	Failure: "TimedOut",
}, {
	Errno:   "EAFNOSUPPORT",
	Failure: "AddressFamilyNotSupported",
}, {
	Errno:   "EADDRINUSE",
	Failure: "AddressInUse",
}, {
	Errno:   "EADDRNOTAVAIL",
	Failure: "AddressNotAvailable",
}, {
	Errno:   "EISCONN",
	Failure: "AlreadyConnected",
}, {
	Errno:   "EFAULT",
	Failure: "BadAddress",
}, {
	Errno:   "EBADF",
	Failure: "BadFileDescriptor",
}, {
	Errno:   "ECONNABORTED",
	Failure: "ConnectionAborted",
}, {
	Errno:   "EALREADY",
	Failure: "ConnectionAlreadyInProgress",
}, {
	Errno:   "EDESTADDRREQ",
	Failure: "DestinationAddressRequired",
}, {
	Errno:   "EINTR",
	Failure: "Interrupted",
}, {
	Errno:   "EINVAL",
	Failure: "InvalidArgument",
}, {
	Errno:   "EMSGSIZE",
	Failure: "MessageSize",
}, {
	Errno:   "ENETDOWN",
	Failure: "NetworkDown",
}, {
	Errno:   "ENETRESET",
	Failure: "NetworkReset",
}, {
	Errno:   "ENETUNREACH",
	Failure: "NetworkUnreachable",
}, {
	Errno:   "ENOBUFS",
	Failure: "NoBufferSpace",
}, {
	Errno:   "ENOPROTOOPT",
	Failure: "NoProtocolOption",
}, {
	Errno:   "ENOTSOCK",
	Failure: "NotASocket",
}, {
	Errno:   "ENOTCONN",
	Failure: "NotConnected",
}, {
	Errno:   "EWOULDBLOCK",
	Failure: "OperationWouldBlock",
}, {
	Errno:   "EACCES",
	Failure: "PermissionDenied",
}, {
	Errno:   "EPROTONOSUPPORT",
	Failure: "ProtocolNotSupported",
}, {
	Errno:   "EPROTOTYPE",
	Failure: "WrongProtocolType",
}}

func fileCreate(filename string) *os.File {
	filep, err := os.Create(filename)
	if err != nil {
		log.Fatal(err)
	}
	return filep
}

func fileWrite(filep *os.File, content string) {
	if _, err := filep.WriteString(content); err != nil {
		log.Fatal(err)
	}
}

func fileClose(filep *os.File) {
	if err := filep.Close(); err != nil {
		log.Fatal(err)
	}
}

func filePrintf(filep *os.File, format string, v ...interface{}) {
	fileWrite(filep, fmt.Sprintf(format, v...))
}

func gofmt(filename string) {
	cmd := execabs.Command("go", "fmt", filename)
	if err := cmd.Run(); err != nil {
		log.Fatal(err)
	}
}

func writeSystemSpecificFile(kind string) {
	filename := "errno_" + kind + ".go"
	filep := fileCreate(filename)
	fileWrite(filep, "// Code generated by go generate; DO NOT EDIT.\n")
	filePrintf(filep, "// Generated: %+v\n\n", time.Now())
	fileWrite(filep, "package errorsx\n\n")
	filePrintf(filep, "import \"golang.org/x/sys/%s\"\n\n", kind)
	fileWrite(filep, "const (\n")
	for _, spec := range Specs {
		filePrintf(filep, "\t%s = %s.%s\n", spec.Errno, kind, spec.Errno)
	}
	fileWrite(filep, ")\n\n")
	fileClose(filep)
	gofmt(filename)
}

func writeGenericFile() {
	filename := "errno.go"
	filep := fileCreate(filename)
	fileWrite(filep, "// Code generated by go generate; DO NOT EDIT.\n")
	filePrintf(filep, "// Generated: %+v\n\n", time.Now())
	fileWrite(filep, "package errorsx\n\n")
	fileWrite(filep, "//go:generate go run ./generator/\n\n")
	fileWrite(filep, "import (\n")
	fileWrite(filep, "\t\"errors\"\n")
	fileWrite(filep, "\t\"syscall\"\n")
	fileWrite(filep, ")\n\n")

	fileWrite(filep, "// This enumeration lists the syscall-derived failures defined at\n")
	fileWrite(filep, "// https://github.com/ooni/spec/blob/master/data-formats/df-007-errors.md\n")
	fileWrite(filep, "//\n")
	fileWrite(filep, "// See also the enumeration at failures.go for the failures that\n")
	fileWrite(filep, "// DO NOT derive from system call errors.\n")
	fileWrite(filep, "const (\n")
	for _, spec := range Specs {
		filePrintf(filep, "\tFailure%s = \"%s\"\n", spec.Failure,
			strcase.ToSnake(spec.Failure))
	}
	fileWrite(filep, ")\n\n")

	fileWrite(filep, "// toSyscallErr converts a syscall error to the\n")
	fileWrite(filep, "// proper OONI error. Returns the OONI error string\n")
	fileWrite(filep, "// on success, an empty string otherwise.\n")
	fileWrite(filep, "func toSyscallErr(err error) string {\n")
	fileWrite(filep, "\t// filter out system errors: necessary to detect all windows errors\n")
	fileWrite(filep, "\t// https://github.com/ooni/probe/issues/1526 describes the problem\n")
	fileWrite(filep, "\t// of mapping localized windows errors.\n")
	fileWrite(filep, "\tvar errno syscall.Errno\n")
	fileWrite(filep, "\tif !errors.As(err, &errno) {\n")
	fileWrite(filep, "\t\treturn \"\"\n")
	fileWrite(filep, "\t}\n")
	fileWrite(filep, "\tswitch errno {\n")
	for _, spec := range Specs {
		if spec.Failure != "" {
			filePrintf(filep, "\tcase %s:\n", spec.Errno)
			filePrintf(filep, "\t\treturn Failure%s\n", spec.Failure)
		}
	}
	fileWrite(filep, "\t}\n")
	fileWrite(filep, "\treturn \"\"\n")
	fileWrite(filep, "}\n\n")

	fileClose(filep)
	gofmt(filename)
}

func writeGenericTestFile() {
	filename := "errno_test.go"
	filep := fileCreate(filename)

	fileWrite(filep, "// Code generated by go generate; DO NOT EDIT.\n")
	filePrintf(filep, "// Generated: %+v\n\n", time.Now())
	fileWrite(filep, "package errorsx\n\n")
	fileWrite(filep, "import (\n")
	fileWrite(filep, "\t\"io\"\n")
	fileWrite(filep, "\t\"syscall\"\n")
	fileWrite(filep, "\t\"testing\"\n")
	fileWrite(filep, ")\n\n")

	fileWrite(filep, "func TestToSyscallErr(t *testing.T) {\n")
	fileWrite(filep, "\tif v := toSyscallErr(io.EOF); v != \"\" {\n")
	fileWrite(filep, "\t\tt.Fatalf(\"expected empty string, got '%s'\", v)\n")
	fileWrite(filep, "\t}\n")

	for _, spec := range Specs {
		filePrintf(filep, "\tif v := toSyscallErr(%s); v != Failure%s {\n", spec.Errno, spec.Failure)
		filePrintf(filep, "\t\tt.Fatalf(\"expected '%%s', got '%%s'\", Failure%s, v)\n", spec.Failure)
		fileWrite(filep, "\t}\n")
	}

	fileWrite(filep, "\tif v := toSyscallErr(syscall.Errno(0)); v != \"\" {\n")
	fileWrite(filep, "\t\tt.Fatalf(\"expected empty string, got '%s'\", v)\n")
	fileWrite(filep, "\t}\n")
	fileWrite(filep, "}\n")

	fileClose(filep)
	gofmt(filename)
}

func main() {
	writeSystemSpecificFile("unix")
	writeSystemSpecificFile("windows")
	writeGenericFile()
	writeGenericTestFile()
}