usgs-api-closure.R

library(httr)

usgsapi <- function () {
  API_URL <- 'https://m2m.cr.usgs.gov/api/api/json/stable/'
  ENDPOINTS <- list(
    login = paste0(API_URL, 'login'),
    permissions = paste0(API_URL, 'permissions'),
    scene_search = paste0(API_URL, 'scene-search')
  )
  TOKEN <- NULL
  
  # internal methods ----
  set_token <- function (token) {
    TOKEN <<- token
  }
  
  get_token <- function () {
    return(TOKEN)
  }
  
  AUTH_HEADER <- function () {
    return(httr::add_headers('X-Auth-Token' = get_token()))
  }
  
  # login function ----
  login <- function (username, password) {
    body <- jsonlite::toJSON(list(
      username = username,
      password = password
    ), auto_unbox = TRUE)
    
    ## run post request
    req <- httr::POST(ENDPOINTS$login,
                           config = list(
                             httr::add_headers('Content-Type' = 'application/json')
                           ),
                           body = body
    )
    ## set token
    res <- httr::content(req)
    TOKEN <<- set_token(res$data)
    
    ## return response
    return(res)
  }
  
  # permissions function ----
  permissions <- function (...) {
    # because the token is within the scope of the parent function (usgsapi)
    # you don't need to provide it manually, you can grap it from the parent scope
    # this also means you can check if you are authenticated, and if not run the
    # login function first
    res <- httr::POST(ENDPOINTS$permissions,
                      add_headers('X-Auth-Token' = get_token()),
                      ...
                     )
    
    return(res)
  }
  
  scene_search <- function (body, ...) {
    req <- httr::POST(ENDPOINTS$scene_search, AUTH_HEADER(), body = body, ...)
    return(req)
  }
  
  return(list(
    get_token = get_token,
    login = login,
    permissions = permissions,
    scene_search = scene_search
  ))
}

# initialize API
api <- usgsapi()

# run login function ----
## runngint this line will also set your token!
res <- api$login(username = "_kmg_", password = "l2Q9B5aZjw8ibf")
res

(token <- api$get_token())

# permissions ----
res <- api$permissions(verbose())
content(res)

# scene search ----
body <- list(
  maxResults = 2,
  datasetName = 'gls_all'
)
(body <- jsonlite::toJSON(body, auto_unbox = TRUE))

res <- api$scene_search(body = body, verbose(), encode = 'json')

jsonlite::toJSON(content(res))

data <- content(res)
data

data$data$results %>% str()
data$data$results[[1]] %>% str()

# try a real request ----
st_bbox_to_poly <- function (bbox) {
  x1 <- bbox[1]
  y1 <- bbox[2]
  x2 <- bbox[3]
  y2 <- bbox[4]
  
  sf::st_polygon(list(matrix(c(
    x1, y1,
    x1, y2,
    x2, y2,
    x2, y1,
    x1, y1
  ), ncol = 2, byrow = TRUE)))
}

poly <- st_bbox_to_poly(shape) %>% 
  sf::st_sfc(crs = 4326) %>% st_as_sf()

(geojson <- geojsonsf::sf_geojson(poly))

body <- list(
  datasetName = 'LANDSAT_8_C1',
  maxResults = 1,
  sceneFilter = list(
    SpatialFilterGeoJson = list(
      filterType = 'geoJson',
      geojson = geojson
    )
  )
)

body

res <- api$scene_search(body = body, verbose(), encode = 'json')
content(res)

jsonlite::toJSON(content(res))