package webdav

import (
	"errors"
	"fmt"
	"io"
	"net/http"
	"strings"
)

var ErrConflict = errors.New("webdav conflict")

type Version struct {
	ETag string
}

type Client struct {
	HTTPClient *http.Client
	BaseURL    string
	Username   string
	Password   string
}

func (c Client) Open(path string) ([]byte, Version, error) {
	req, err := http.NewRequest(http.MethodGet, c.url(path), nil)
	if err != nil {
		return nil, Version{}, fmt.Errorf("build GET request: %w", err)
	}
	c.applyAuth(req)

	resp, err := c.httpClient().Do(req)
	if err != nil {
		return nil, Version{}, fmt.Errorf("GET %s: %w", path, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, Version{}, fmt.Errorf("GET %s: unexpected status %d", path, resp.StatusCode)
	}

	content, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, Version{}, fmt.Errorf("read %s: %w", path, err)
	}

	return content, Version{ETag: resp.Header.Get("ETag")}, nil
}

func (c Client) Save(path string, content io.Reader, version Version) (Version, error) {
	req, err := http.NewRequest(http.MethodPut, c.url(path), content)
	if err != nil {
		return Version{}, fmt.Errorf("build PUT request: %w", err)
	}
	c.applyAuth(req)
	if version.ETag != "" {
		req.Header.Set("If-Match", version.ETag)
	}

	resp, err := c.httpClient().Do(req)
	if err != nil {
		return Version{}, fmt.Errorf("PUT %s: %w", path, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusPreconditionFailed {
		return Version{}, ErrConflict
	}
	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusNoContent {
		return Version{}, fmt.Errorf("PUT %s: unexpected status %d", path, resp.StatusCode)
	}

	return Version{ETag: resp.Header.Get("ETag")}, nil
}

func (c Client) httpClient() *http.Client {
	if c.HTTPClient != nil {
		return c.HTTPClient
	}
	return http.DefaultClient
}

func (c Client) applyAuth(req *http.Request) {
	if c.Username == "" && c.Password == "" {
		return
	}
	req.SetBasicAuth(c.Username, c.Password)
}

func (c Client) url(path string) string {
	base := strings.TrimRight(c.BaseURL, "/")
	path = strings.TrimLeft(path, "/")
	return base + "/" + path
}