package commands

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"

	"github.com/golangci/golangci-lint/pkg/printers"
	"github.com/golangci/golangci-lint/pkg/report"
	"github.com/golangci/golangci-lint/pkg/result"
)

var ErrNoResult = errors.New("could not read result")

func ReadResultsFile(filePath string) (report *report.Data, issues []result.Issue, err error) {
	if filePath == "" {
		return nil, nil, ErrNoResult
	}

	f, err := os.Open(filePath)
	if err != nil {
		return nil, nil, err
	}

	defer func() {
		err = errors.Join(err, f.Close())
	}()

	return ReadResults(f)
}

func ReadResults(reader io.Reader) (*report.Data, []result.Issue, error) {
	decoder := json.NewDecoder(reader)
	var printerResult printers.JSONResult
	if err := decoder.Decode(&printerResult); err != nil {
		return nil, nil, err
	}

	return printerResult.Report, printerResult.Issues, nil
}

func RunGolangCiLint(ctx context.Context, extraFlags []string) (*report.Data, []result.Issue, error) {
	const defaultArgsLen = 3
	golangCiLintArgs := make([]string, 1, defaultArgsLen+len(extraFlags))
	golangCiLintArgs[0] = "run"
	golangCiLintArgs = append(golangCiLintArgs, extraFlags...)
	golangCiLintArgs = append(golangCiLintArgs, "--issues-exit-code=0", "--out-format=json")

	golangCiLintArgs = append(golangCiLintArgs, extraFlags...)

	cmd := exec.CommandContext(
		ctx,
		"golangci-lint",
		golangCiLintArgs...,
	)

	stderrBuf := bytes.NewBuffer(nil)

	cmd.Stderr = stderrBuf

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return nil, nil, err
	}

	if err := cmd.Start(); err != nil {
		return nil, nil, err
	}

	var printerResult printers.JSONResult

	if err := json.NewDecoder(stdout).Decode(&printerResult); err != nil {
		return nil, nil, err
	}

	if err := cmd.Wait(); err != nil {
		return nil, nil, fmt.Errorf("stderr: %s - %w", stderrBuf.String(), err)
	}

	return printerResult.Report, printerResult.Issues, nil
}