# LIBRARIES ----
library(tidyquant)
library(tidyverse)
library(broom)

# devtools::install_github("rstudio/fontawesome")
library(gt)
library(fontawesome)
library(htmltools)

# DATA ----
mpg

# 1.0 GROUP SPLIT ----
# - Turns a grouped data frame into an list of data frames (iterable)
# - Iteration & functions - Covered in Week 5 of DS4B 101-R

# Group Split
mpg %>%
  mutate(manufacturer = as_factor(manufacturer)) %>%
  group_by(manufacturer) %>%
  group_split()

# We can now iterate with map()
mpg %>%
  mutate(manufacturer = as_factor(manufacturer)) %>%
  group_by(manufacturer) %>%
  group_split() %>%

  map(.f = function(df) {
    lm(hwy ~ cty, data = df)
  })

# 2.0 POWER OF BROOM ----
# - Tidy up our linear regression metrics with glance()
# - Modeling & Machine Learning - Covered in Week 6 of DS4B 101-R Course

hwy_vs_city_tbl <- mpg %>%
  mutate(manufacturer = as_factor(manufacturer)) %>%
  group_by(manufacturer) %>%
  group_split() %>%

  map_dfr(.f = function(df) {
    lm(hwy ~ cty, data = df) %>%
      glance() %>%
      add_column(manufacturer = unique(df$manufacturer), .before = 1)
  })

# 3.0 SUPER AWESOME TABLE WITH GT PACKAGE ----

# Source: https://themockup.blog/posts/2020-10-31-embedding-custom-features-in-gt-tables/
rating_stars <- function(rating, max_rating = 5) {
  rounded_rating <- floor(rating + 0.5)  # always round up
  stars <- lapply(seq_len(max_rating), function(i) {
    if (i <= rounded_rating) {
      fontawesome::fa("star", fill= "orange")
    } else {
      fontawesome::fa("star", fill= "grey")
    }
  })
  label <- sprintf("%s out of %s", rating, max_rating)
  div_out <- div(title = label, "aria-label" = label, role = "img", stars)

  as.character(div_out) %>%
    gt::html()
}

hwy_vs_city_tbl %>%
  dplyr::select(manufacturer, nobs, r.squared, adj.r.squared, p.value) %>%
  mutate(manufacturer = str_to_title(manufacturer)) %>%
  mutate(rating = cut_number(r.squared, n = 5) %>% as.numeric()) %>%
  mutate(rating = map(rating, rating_stars)) %>%
  arrange(desc(r.squared)) %>%
  gt() %>%
  tab_header(title = gt::md("__Highway vs City Fuel Mileage__")) %>%
  tab_spanner(
    label = gt::html("<small>Relationship Strength (hwy ~ cty)</small>"),
    columns = vars(r.squared, adj.r.squared, p.value)
  ) %>%
  fmt_number(columns = vars(r.squared, adj.r.squared)) %>%
  fmt_number(columns = vars(p.value), decimals = 3) %>%
  tab_style(
    style = cell_text(size = px(12)),
    locations = cells_body(
      columns = vars(r.squared, adj.r.squared, p.value))
  ) %>%
  cols_label(
    manufacturer = gt::md("__MFG__"),
    nobs = gt::md("__#__"),
    r.squared = gt::html(glue::glue("<strong>R-Squared ", fontawesome::fa("arrow-down", fill = "orange"), "</strong>")),
    adj.r.squared = gt::md("__R-Squared (Adj)__"),
    p.value = gt::md("__P-Value__"),
    rating  = gt::md("__Rating__")
  )