package api

import (
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	"strconv"
	"strings"

	"github.com/cli/cli/context"
	"github.com/spf13/cobra"
)

type ApiOptions struct {
	RequestMethod       string
	RequestMethodPassed bool
	RequestPath         string
	MagicFields         []string
	RawFields           []string
	RequestHeaders      []string
	ShowResponseHeaders bool

	HttpClient func() (*http.Client, error)
}

func NewCmdApi() *cobra.Command {
	opts := ApiOptions{}
	cmd := &cobra.Command{
		Use:   "api <endpoint>",
		Short: "Make an authenticated GitHub API request",
		Long: `Makes an authenticated HTTP request to the GitHub API and prints the response.

The <endpoint> argument should either be a path of a GitHub API v3 endpoint, or
"graphql" to access the GitHub API v4.

The default HTTP request method is "GET" normally and "POST" if any parameters
were added. Override the method with '--method'.

Pass one or more '--raw-field' values in "<key>=<value>" format to add
JSON-encoded string parameters to the POST body.

The '--field' flag behaves like '--raw-field' with magic type conversion based
on the format of the value:

- literal values "true", "false", "null", and integer numbers get converted to
  appropriate JSON types;
- if the value starts with "@", the rest of the value is interpreted as a
  filename to read the value from. Pass "-" to read from standard input.
`,
		Args: cobra.ExactArgs(1),
		RunE: func(c *cobra.Command, args []string) error {
			opts.RequestPath = args[0]
			opts.RequestMethodPassed = c.Flags().Changed("method")

			opts.HttpClient = func() (*http.Client, error) {
				ctx := context.New()
				token, err := ctx.AuthLogin()
				if err != nil {
					return nil, err
				}
				return apiClientFromContext(token), nil
			}

			return apiRun(&opts)
		},
	}

	cmd.Flags().StringVarP(&opts.RequestMethod, "method", "X", "GET", "The HTTP method for the request")
	cmd.Flags().StringArrayVarP(&opts.MagicFields, "field", "F", nil, "Add a parameter of inferred type")
	cmd.Flags().StringArrayVarP(&opts.RawFields, "raw-field", "f", nil, "Add a string parameter")
	cmd.Flags().StringArrayVarP(&opts.RequestHeaders, "header", "H", nil, "Add an additional HTTP request header")
	cmd.Flags().BoolVarP(&opts.ShowResponseHeaders, "include", "i", false, "Include HTTP response headers in the output")
	return cmd
}

func apiRun(opts *ApiOptions) error {
	params, err := parseFields(opts)
	if err != nil {
		return err
	}

	method := opts.RequestMethod
	if len(params) > 0 && !opts.RequestMethodPassed {
		method = "POST"
	}

	httpClient, err := opts.HttpClient()
	if err != nil {
		return err
	}

	resp, err := httpRequest(httpClient, method, opts.RequestPath, params, opts.RequestHeaders)
	if err != nil {
		return err
	}

	if opts.ShowResponseHeaders {
		for name, vals := range resp.Header {
			fmt.Printf("%s: %s\r\n", name, strings.Join(vals, ", "))
		}
		fmt.Print("\r\n")
	}

	if resp.StatusCode == 204 {
		return nil
	}
	defer resp.Body.Close()

	// TODO: make stdout configurable for tests
	_, err = io.Copy(os.Stdout, resp.Body)
	if err != nil {
		return err
	}

	return nil
}

func parseFields(opts *ApiOptions) (map[string]interface{}, error) {
	params := make(map[string]interface{})
	for _, f := range opts.RawFields {
		key, value, err := parseField(f)
		if err != nil {
			return params, err
		}
		params[key] = value
	}
	for _, f := range opts.MagicFields {
		key, strValue, err := parseField(f)
		if err != nil {
			return params, err
		}
		value, err := magicFieldValue(strValue)
		if err != nil {
			return params, fmt.Errorf("error parsing %q value: %w", key, err)
		}
		params[key] = value
	}
	return params, nil
}

func parseField(f string) (string, string, error) {
	idx := strings.IndexRune(f, '=')
	if idx == -1 {
		return f, "", fmt.Errorf("field %q requires a value separated by an '=' sign", f)
	}
	return f[0:idx], f[idx+1:], nil
}

func magicFieldValue(v string) (interface{}, error) {
	if strings.HasPrefix(v, "@") {
		return readUserFile(v[1:])
	}

	if n, err := strconv.Atoi(v); err != nil {
		return n, nil
	}

	switch v {
	case "true":
		return true, nil
	case "false":
		return false, nil
	case "null":
		return nil, nil
	default:
		return v, nil
	}
}

func readUserFile(fn string) ([]byte, error) {
	var r io.ReadCloser
	if fn == "-" {
		// TODO: make stdin configurable for tests
		r = os.Stdin
	} else {
		var err error
		r, err = os.Open(fn)
		if err != nil {
			return nil, err
		}
		defer r.Close()
	}
	return ioutil.ReadAll(r)
}