package cmd

import (
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"time"

	"github.com/nihei9/maleeni/compiler"
	"github.com/nihei9/maleeni/spec"
	"github.com/spf13/cobra"
)

func init() {
	cmd := &cobra.Command{
		Use:     "compile",
		Short:   "Compile a lexical specification into a DFA",
		Long:    `compile takes a lexical specification and generates a DFA accepting the tokens described in the specification.`,
		Example: `  cat lexspec.json | maleeni compile > clexspec.json`,
		RunE:    runCompile,
	}
	rootCmd.AddCommand(cmd)
}

func runCompile(cmd *cobra.Command, args []string) (retErr error) {
	lspec, err := readLexSpec()
	if err != nil {
		return fmt.Errorf("Cannot read a lexical specification: %w", err)
	}
	var w io.Writer
	{
		fileName := "maleeni-compile.log"
		f, err := os.OpenFile(fileName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
		if err != nil {
			return fmt.Errorf("Cannot open the log file %s: %w", fileName, err)
		}
		defer f.Close()
		w = f
	}
	fmt.Fprintf(w, `maleeni compile starts.
Date time: %v
---
`, time.Now().Format(time.RFC3339))
	defer func() {
		fmt.Fprintf(w, "---\n")
		if retErr != nil {
			fmt.Fprintf(w, "maleeni compile failed: %v\n", retErr)
		} else {
			fmt.Fprintf(w, "maleeni compile succeeded.\n")
		}
	}()
	clspec, err := compiler.Compile(lspec, compiler.EnableLogging(w))
	if err != nil {
		return err
	}
	err = writeCompiledLexSpec(clspec)
	if err != nil {
		return fmt.Errorf("Cannot write a compiled lexical specification: %w", err)
	}

	return nil
}

func readLexSpec() (*spec.LexSpec, error) {
	data, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		return nil, err
	}
	lspec := &spec.LexSpec{}
	err = json.Unmarshal(data, lspec)
	if err != nil {
		return nil, err
	}
	return lspec, nil
}

func writeCompiledLexSpec(clspec *spec.CompiledLexSpec) error {
	out, err := json.Marshal(clspec)
	if err != nil {
		return err
	}
	fmt.Fprintf(os.Stdout, "%v\n", string(out))
	return nil
}