// Copyright 2015 The go-python Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"

	"github.com/gonuts/commander"
	"github.com/gonuts/flag"

	"github.com/go-python/gopy/bind"
)

func gopyMakeCmdBuild() *commander.Command {
	cmd := &commander.Command{
		Run:       gopyRunCmdBuild,
		UsageLine: "build <go-package-name> [other-go-package...]",
		Short:     "generate and compile (C)Python language bindings for Go",
		Long: `
build generates and compiles (C)Python language bindings for Go package(s).

ex:
 $ gopy build [options] <go-package-name> [other-go-package...]
 $ gopy build github.com/go-python/gopy/_examples/hi
`,
		Flag: *flag.NewFlagSet("gopy-build", flag.ExitOnError),
	}

	cmd.Flag.String("vm", "python", "path to python interpreter")
	cmd.Flag.String("output", "", "output directory for bindings")
	cmd.Flag.String("name", "", "name of output package (otherwise name of first package is used)")
	cmd.Flag.String("main", "", "code string to run in the go main() function in the cgo library")
	cmd.Flag.String("package-prefix", ".", "custom package prefix used when generating import "+
		"statements for generated package")
	cmd.Flag.Bool("rename", false, "rename Go symbols to python PEP snake_case")
	cmd.Flag.Bool("symbols", true, "include symbols in output")
	cmd.Flag.Bool("no-warn", false, "suppress warning messages, which may be expected")
	cmd.Flag.Bool("no-make", false, "do not generate a Makefile, e.g., when called from Makefile")
	cmd.Flag.Bool("dynamic-link", false, "whether to link output shared library dynamically to Python")
	cmd.Flag.String("build-tags", "", "build tags to be passed to `go build`")
	return cmd
}

func gopyRunCmdBuild(cmdr *commander.Command, args []string) error {
	if len(args) == 0 {
		err := fmt.Errorf("gopy: expect a fully qualified go package name as argument")
		log.Println(err)
		return err
	}

	cfg := NewBuildCfg()
	cfg.OutputDir = cmdr.Flag.Lookup("output").Value.Get().(string)
	cfg.Name = cmdr.Flag.Lookup("name").Value.Get().(string)
	cfg.Main = cmdr.Flag.Lookup("main").Value.Get().(string)
	cfg.VM = cmdr.Flag.Lookup("vm").Value.Get().(string)
	cfg.PkgPrefix = cmdr.Flag.Lookup("package-prefix").Value.Get().(string)
	cfg.RenameCase = cmdr.Flag.Lookup("rename").Value.Get().(bool)
	cfg.Symbols = cmdr.Flag.Lookup("symbols").Value.Get().(bool)
	cfg.NoWarn = cmdr.Flag.Lookup("no-warn").Value.Get().(bool)
	cfg.NoMake = cmdr.Flag.Lookup("no-make").Value.Get().(bool)
	cfg.DynamicLinking = cmdr.Flag.Lookup("dynamic-link").Value.Get().(bool)
	cfg.BuildTags = cmdr.Flag.Lookup("build-tags").Value.Get().(string)

	bind.NoWarn = cfg.NoWarn
	bind.NoMake = cfg.NoMake

	for _, path := range args {
		bpkg, err := loadPackage(path, true, cfg.BuildTags) // build first
		if err != nil {
			return fmt.Errorf("gopy-gen: go build / load of package failed with path=%q: %v", path, err)
		}
		pkg, err := parsePackage(bpkg)
		if err != nil {
			return err
		}
		if cfg.Name == "" {
			cfg.Name = pkg.Name()
		}
	}
	return runBuild("build", cfg)
}

// runBuild calls genPkg and then executes commands to build the resulting files
// exe = executable mode to build an executable instead of a library
// mode = gen, build, pkg, exe
func runBuild(mode bind.BuildMode, cfg *BuildCfg) error {
	var err error
	cfg.OutputDir, err = genOutDir(cfg.OutputDir)
	if err != nil {
		return err
	}
	err = genPkg(mode, cfg)
	if err != nil {
		return err
	}

	fmt.Printf("\n--- building package ---\n%s\n", cfg.Cmd)

	buildname := cfg.Name + "_go"
	var cmdout []byte
	cwd, err := os.Getwd()
	os.Chdir(cfg.OutputDir)
	defer os.Chdir(cwd)

	os.Remove(cfg.Name + ".c") // may fail, we don't care

	fmt.Printf("goimports -w %v\n", cfg.Name+".go")
	cmd := exec.Command("goimports", "-w", cfg.Name+".go")
	cmdout, err = cmd.CombinedOutput()
	if err != nil {
		fmt.Printf("cmd had error: %v  output:\no%v\n", err, string(cmdout))
		return err
	}

	pycfg, err := bind.GetPythonConfig(cfg.VM)

	if mode == bind.ModeExe {
		of, err := os.Create(buildname + ".h") // overwrite existing
		fmt.Fprintf(of, "typedef uint8_t bool;\n")
		of.Close()

		fmt.Printf("%v build.py   # will fail, but needed to generate .c file\n", cfg.VM)
		cmd = exec.Command(cfg.VM, "build.py")
		cmd.Run() // will fail, we don't care about errors

		args := []string{"build", "-mod=mod", "-buildmode=c-shared"}
		if cfg.BuildTags != "" {
			args = append(args, "-tags", cfg.BuildTags)
		}
		args = append(args, "-o", buildname+libExt, ".")

		fmt.Printf("go %v\n", strings.Join(args, " "))
		cmd = exec.Command("go", args...)
		cmdout, err = cmd.CombinedOutput()
		if err != nil {
			fmt.Printf("cmd had error: %v  output:\n%v\n", err, string(cmdout))
			return err
		}

		fmt.Printf("%v build.py   # should work this time\n", cfg.VM)
		cmd = exec.Command(cfg.VM, "build.py")
		cmdout, err = cmd.CombinedOutput()
		if err != nil {
			fmt.Printf("cmd had error: %v  output:\n%v\n", err, string(cmdout))
			return err
		}

		err = os.Remove(cfg.Name + "_go" + libExt)

		fmt.Printf("go build -o py%s\n", cfg.Name)
		cmd = exec.Command("go", "build", "-mod=mod")
		if cfg.BuildTags != "" {
			args = append(args, "-tags", cfg.BuildTags)
		}
		args = append(args, "-o", "py"+cfg.Name)
		cmdout, err = cmd.CombinedOutput()
		if err != nil {
			fmt.Printf("cmd had error: %v  output:\n%v\n", err, string(cmdout))
			return err
		}

	} else {
		buildLib := buildname + libExt
		extext := libExt
		if runtime.GOOS == "windows" {
			extext = ".pyd"
		}
		if pycfg.ExtSuffix != "" {
			extext = pycfg.ExtSuffix
		}
		modlib := "_" + cfg.Name + extext

		// build the go shared library upfront to generate the header
		// needed by our generated cpython code
		args := []string{"build", "-mod=mod", "-buildmode=c-shared"}
		if cfg.BuildTags != "" {
			args = append(args, "-tags", cfg.BuildTags)
		}
		if !cfg.Symbols {
			// These flags will omit the various symbol tables, thereby
			// reducing the final size of the binary. From https://golang.org/cmd/link/
			// -s Omit the symbol table and debug information
			// -w Omit the DWARF symbol table
			args = append(args, "-ldflags=-s -w")
		}
		args = append(args, "-o", buildLib, ".")
		fmt.Printf("go %v\n", strings.Join(args, " "))
		cmd = exec.Command("go", args...)
		cmdout, err = cmd.CombinedOutput()
		if err != nil {
			fmt.Printf("cmd had error: %v  output:\n%v\n", err, string(cmdout))
			return err
		}
		// update the output name to the one with the ABI extension
		args[len(args)-2] = modlib
		// we don't need this initial lib because we are going to relink
		os.Remove(buildLib)

		// generate c code
		fmt.Printf("%v build.py\n", cfg.VM)
		cmd = exec.Command(cfg.VM, "build.py")
		cmdout, err = cmd.CombinedOutput()
		if err != nil {
			fmt.Printf("cmd had error: %v  output:\no%v\n", err, string(cmdout))
			return err
		}

		if bind.WindowsOS {
			fmt.Printf("Doing windows sed hack to fix declspec for PyInit\n")
			fname := cfg.Name + ".c"
			raw, err := os.ReadFile(fname)
			if err != nil {
				fmt.Printf("could not read %s: %+v", fname, err)
				return fmt.Errorf("could not read %s: %w", fname, err)
			}
			raw = bytes.ReplaceAll(raw, []byte(" PyInit_"), []byte(" __declspec(dllexport) PyInit_"))
			err = os.WriteFile(fname, raw, 0644)
			if err != nil {
				fmt.Printf("could not apply sed hack to fix declspec for PyInit: %+v", err)
				return fmt.Errorf("could not apply sed hack to fix PyInit: %w", err)
			}
		}

		cflags := strings.Fields(strings.TrimSpace(pycfg.CFlags))
		cflags = append(cflags, "-fPIC", "-Ofast")
		if include, exists := os.LookupEnv("GOPY_INCLUDE"); exists {
			cflags = append(cflags, "-I"+filepath.ToSlash(include))
		}
		var ldflags []string
		if cfg.DynamicLinking {
			ldflags = strings.Fields(strings.TrimSpace(pycfg.LdDynamicFlags))
		} else {
			ldflags = strings.Fields(strings.TrimSpace(pycfg.LdFlags))
		}
		if !cfg.Symbols {
			ldflags = append(ldflags, "-s")
		}
		if lib, exists := os.LookupEnv("GOPY_LIBDIR"); exists {
			ldflags = append(ldflags, "-L"+filepath.ToSlash(lib))
		}
		if libname, exists := os.LookupEnv("GOPY_PYLIB"); exists {
			ldflags = append(ldflags, "-l"+filepath.ToSlash(libname))
		}

		removeEmpty := func(src []string) []string {
			o := make([]string, 0, len(src))
			for _, v := range src {
				if v == "" {
					continue
				}
				o = append(o, v)
			}
			return o
		}

		cflags = removeEmpty(cflags)
		ldflags = removeEmpty(ldflags)

		cflagsEnv := fmt.Sprintf("CGO_CFLAGS=%s", strings.Join(cflags, " "))
		ldflagsEnv := fmt.Sprintf("CGO_LDFLAGS=%s", strings.Join(ldflags, " "))

		env := os.Environ()
		env = append(env, cflagsEnv)
		env = append(env, ldflagsEnv)

		fmt.Println(cflagsEnv)
		fmt.Println(ldflagsEnv)

		// build extension with go + c
		fmt.Printf("go %v\n", strings.Join(args, " "))
		cmd = exec.Command("go", args...)
		cmd.Env = env
		cmdout, err = cmd.CombinedOutput()
		if err != nil {
			fmt.Printf("cmd had error: %v  output:\n%v\n", err, string(cmdout))
			return err
		}
	}

	return err
}