local M = {}

M.bg = "#000000"
M.fg = "#ffffff"
M.day_brightness = 0.3

---@param c  string
local function hexToRgb(c)
  c = string.lower(c)
  return { tonumber(c:sub(2, 3), 16), tonumber(c:sub(4, 5), 16), tonumber(c:sub(6, 7), 16) }
end

---@param fg string foreground color
---@param bg string background color
---@param alpha number number between 0 and 1. 0 results in bg, 1 results in fg
function M.blend(fg, bg, alpha)
  bg = hexToRgb(bg)
  fg = hexToRgb(fg)

  local blendChannel = function(i)
    local ret = (alpha * fg[i] + ((1 - alpha) * bg[i]))
    return math.floor(math.min(math.max(0, ret), 255) + 0.5)
  end

  return string.format("#%02x%02x%02x", blendChannel(1), blendChannel(2), blendChannel(3))
end

function M.darken(hex, amount, bg)
  return M.blend(hex, bg or M.bg, math.abs(amount))
end
function M.lighten(hex, amount, fg)
  return M.blend(hex, fg or M.fg, math.abs(amount))
end

function M.invert_color(color)
  local hsluv = require("tokyonight.hsluv")
  if color ~= "NONE" then
    local hsl = hsluv.hex_to_hsluv(color)
    hsl[3] = 100 - hsl[3]
    if hsl[3] < 40 then
      hsl[3] = hsl[3] + (100 - hsl[3]) * M.day_brightness
    end
    return hsluv.hsluv_to_hex(hsl)
  end
  return color
end

function M.highlight(group, color)
  local hl = { fg = color.fg, bg = color.bg, sp = color.sp, link = color.link }
  if color.style and color.style:lower() ~= "none" then
    for s in string.gmatch(color.style, "([^,]+)") do
      hl[s] = true
    end
  end
  vim.api.nvim_set_hl(0, group, hl)
end

--- Delete the autocmds when the theme changes to something else
function M.onColorScheme()
  if vim.g.colors_name ~= "tokyonight" then
    vim.cmd([[autocmd! TokyoNight]])
    vim.cmd([[augroup! TokyoNight]])
  end
end

---@param config Config
function M.autocmds(config)
  vim.cmd([[augroup TokyoNight]])
  vim.cmd([[  autocmd!]])
  vim.cmd([[  autocmd ColorScheme * lua require("tokyonight.util").onColorScheme()]])
  for _, sidebar in ipairs(config.sidebars) do
    if sidebar == "terminal" then
      vim.cmd([[  autocmd TermOpen * setlocal winhighlight=Normal:NormalSB,SignColumn:SignColumnSB]])
    else
      vim.cmd([[  autocmd FileType ]] .. sidebar .. [[ setlocal winhighlight=Normal:NormalSB,SignColumn:SignColumnSB]])
    end
  end
  vim.cmd([[augroup end]])
end

-- Simple string interpolation.
--
-- Example template: "${name} is ${value}"
--
---@param str string template string
---@param table table key value pairs to replace in the string
function M.template(str, table)
  return (str:gsub("($%b{})", function(w)
    return table[w:sub(3, -2)] or w
  end))
end

function M.syntax(syntax)
  for group, colors in pairs(syntax) do
    M.highlight(group, colors)
  end
end

---@param colors ColorScheme
function M.terminal(colors)
  -- dark
  vim.g.terminal_color_0 = colors.black
  vim.g.terminal_color_8 = colors.terminal_black

  -- light
  vim.g.terminal_color_7 = colors.fg_dark
  vim.g.terminal_color_15 = colors.fg

  -- colors
  vim.g.terminal_color_1 = colors.red
  vim.g.terminal_color_9 = colors.red

  vim.g.terminal_color_2 = colors.green
  vim.g.terminal_color_10 = colors.green

  vim.g.terminal_color_3 = colors.yellow
  vim.g.terminal_color_11 = colors.yellow

  vim.g.terminal_color_4 = colors.blue
  vim.g.terminal_color_12 = colors.blue

  vim.g.terminal_color_5 = colors.magenta
  vim.g.terminal_color_13 = colors.magenta

  vim.g.terminal_color_6 = colors.cyan
  vim.g.terminal_color_14 = colors.cyan
end

---@param colors ColorScheme
function M.invert_colors(colors)
  if type(colors) == "string" then
    ---@diagnostic disable-next-line: return-type-mismatch
    return M.invert_color(colors)
  end
  for key, value in pairs(colors) do
    colors[key] = M.invert_colors(value)
  end
end

---@param hls Highlights
function M.invert_highlights(hls)
  for _, hl in pairs(hls) do
    if hl.fg then
      hl.fg = M.invert_color(hl.fg)
    end
    if hl.bg then
      hl.bg = M.invert_color(hl.bg)
    end
    if hl.sp then
      hl.sp = M.invert_color(hl.sp)
    end
  end
end

---@param theme Theme
function M.load(theme)
  -- only needed to clear when not the default colorscheme
  if vim.g.colors_name then
    vim.cmd("hi clear")
  end

  vim.o.termguicolors = true
  vim.g.colors_name = "tokyonight"

  M.syntax(theme.highlights)

  -- vim.api.nvim_set_hl_ns(M.ns)
  if theme.config.terminal_colors then
    M.terminal(theme.colors)
  end

  M.autocmds(theme.config)

  vim.defer_fn(function()
    M.syntax(theme.defer)
  end, 100)
end

return M