local M = {}

HlPrefix = "SL_Highlight_"
Colors = {
    { name = "Red",                       ctermfg = "red",       fg = "red" },
    { name = "Green",                     ctermfg = "green",     fg = "green" },
    { name = "Blue",                      ctermfg = "blue",      fg = "blue" },
    { name = "Black on Red",              ctermfg = "black",     ctermbg = "magenta",   fg = "black", bg = "IndianRed" },
    { name = "Black on Green",            ctermfg = "black",     ctermbg = "green",     fg = "black", bg = "chartreuse" },
    { name = "Black on Cyan",             ctermfg = "black",     ctermbg = "cyan",      fg = "black", bg = "DeepSkyBlue" },
    { name = "White on Red",              ctermfg = "white",     ctermbg = "DarkRed",   fg = "white", bg = "firebrick" },
    { name = "White on Green",            ctermfg = "white",     ctermbg = "DarkGreen", fg = "white", bg = "DarkGreen" },
    { name = "White on Blue",             ctermfg = "white",     ctermbg = "DarkBlue",  fg = "white", bg = "DarkSlateBlue" },
    { name = "Black on White",            fg = "black",          bg = "thistle" },
    { name = "Black on Baige",            fg = "black",          bg = "burlywood" },
    { name = "Black on Powder Blue",      fg = "black",          bg = "PowderBlue" },
    { name = "Black on Orange",           fg = "black",          bg = "peru" },
    { name = "Black on Dark Sea Green",   fg = "black",          bg = "DarkSeaGreen" },
    { name = "Black on Steel Blue",       fg = "black",          bg = "SteelBlue" },
    { name = "Black on Dark Orange",      fg = "black",          bg = "DarkOrange" },
    { name = "Black on Dark Olive Green", fg = "black",          bg = "DarkOliveGreen" },
    { name = "Black on Slate Gray",       fg = "black",          bg = "SlateGray" },
    { name = "Red on Dark Grey",          fg = "red",            bg = "grey20" },
    { name = "Green on Dark Grey",        fg = "green",          bg = "grey20" },
    { name = "Blue on Dark Grey",         fg = "CornflowerBlue", bg = "grey20" },
    { name = "Red on Semi Dark Grey",     fg = "red",            bg = "grey40" },
    { name = "Green on Semi Dark Grey",   fg = "green",          bg = "grey40" },
    { name = "Blue on Semi Dark Grey",    fg = "blue",           bg = "grey40" },
    { name = "Red on Grey",               fg = "red",            bg = "grey70" },
    { name = "Green on Grey",             fg = "DarkGreen",      bg = "grey70" },
    { name = "Blue on Grey",              fg = "blue",           bg = "grey70" },
}
ActiveHighlights = {}

M.setup = function()
    table.sort(Colors, function(a, b) return a.name < b.name end)
    -- Defining highlight groups
    for _, v in ipairs(Colors) do
        local params = {}
        for field, value in pairs(v) do
            if field == "name" then
                goto continue
            end
            params[field] = value
            ::continue::
        end
        local key = (v.ctermfg or "") .. (v.ctermbg or "") .. (v.fg or "") .. (v.bg or "")
        vim.api.nvim_set_hl(0, HlPrefix .. key, params)
    end

    -- Defining command for applying highlight
    vim.api.nvim_create_user_command(
        "HL",
        function(opts)
            PerformHighlight(opts)
        end,
        {
            desc = "idk",
            range = true,
        }
    )

    -- Defining command for applying random highlight
    vim.api.nvim_create_user_command(
        "HLR",
        function(opts)
            PerformHighlight(opts, true)
        end,
        {
            desc = "idk",
            range = true,
        }
    )


    -- Defining command for opening highlight removal menu
    vim.api.nvim_create_user_command(
        "HC",
        function(opts) ClearHighlight(opts) end,
        {
            desc = "idk",
            range = true,
        }
    )

    vim.keymap.set({ "n", "v" }, "<leader>hl", function()
        vim.api.nvim_command(":HL")
    end)
    vim.keymap.set({ "n", "v" }, "<leader>hh", function()
        vim.api.nvim_command(":HLR")
    end)
end

function PreparePatternForMatch(pattern)
    pattern = string.gsub(pattern, "%[", "\\[")
    pattern = string.gsub(pattern, "%]", "\\]")
    pattern = string.gsub(pattern, "%*", "\\*")
    return pattern
end

function PerformHighlight(opts, random)
    random = random or false
    local pattern = ""

    local mode = vim.api.nvim_get_mode().mode
    -- If command argument provided, use it whole as highlight pattern
    if string.len(opts.args) > 0 then
        pattern = opts.args
        -- If command is called with visual selection, extract text and use as pattern
    elseif opts.range > 0 then
        local region = vim.fn.getregion(
            vim.fn.getpos("'<"),
            vim.fn.getpos("'>"),
            { type = vim.fn.visualmode() }
        )
        pattern = table.concat(region, "\\n")
    elseif vim.fn.getpos("v") ~= vim.fn.getpos(".") and (mode:match("^v") or mode:match("^V")) then
        vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes("<Esc>", true, false, true), 'nx', false)
        local s = vim.fn.getpos("'<")
        local e = vim.fn.getpos("'>")
        local reg_opts = {
            -- type = mode:match("^v") and "char" or mode:match("^V") and "line" or "block"
            type = "v"
        }

        local lines = vim.fn.getregion(s, e, reg_opts)
        pattern = table.concat(lines, "\\n")
        -- If nothing is provided, use current word under the cursor
    else
        pattern = vim.fn.expand("<cword>")
    end

    if not random then
        local options = {}

        -- Defining options for highlight selection menu
        for _, v in ipairs(Colors) do
            table.insert(options, v.name)
        end
        -- Opening highlight selection menu
        vim.ui.select(
            options,
            { prompt = "Select highlight:" },
            function(_, index)
                if index == nil then
                    return
                end
                local v = Colors[index]
                local key = (v.ctermfg or "") .. (v.ctermbg or "") .. (v.fg or "") .. (v.bg or "")
                local match_pattern = PreparePatternForMatch(pattern)
                local match_id = vim.fn.matchadd(HlPrefix .. key, match_pattern, 10, -1)
                table.insert(ActiveHighlights, {
                    id = match_id,
                    pattern = pattern,
                    hl = HlPrefix .. key,
                })
            end
        )

        -- Call matchadd function on highlight selection menu to provide highlighting preview
        vim.defer_fn(function()
            local win = vim.api.nvim_get_current_win()
            for i, v in ipairs(Colors) do
                local key = (v.ctermfg or "") .. (v.ctermbg or "") .. (v.fg or "") .. (v.bg or "")
                vim.fn.matchadd(HlPrefix .. key, i .. ". " .. v.name, 10, -1, { window = win + 1 })
            end
        end, 50)
    else
        local index = math.random(#Colors)
        local v = Colors[index]
        local key = (v.ctermfg or "") .. (v.ctermbg or "") .. (v.fg or "") .. (v.bg or "")
        local match_pattern = PreparePatternForMatch(pattern)
        local match_id = vim.fn.matchadd(HlPrefix .. key, match_pattern, 10, -1)
        table.insert(ActiveHighlights, {
            id = match_id,
            pattern = pattern,
            hl = HlPrefix .. key,
        })
    end
end

function ClearHighlight(opts)
    if opts.args == "*" then
        vim.fn.clearmatches()
        return
    end

    local options = { "All" }
    for _, v in ipairs(ActiveHighlights) do
        table.insert(options, v.pattern)
    end

    vim.ui.select(
        options,
        { prompt = "Select highlight:" },
        function(_, index)
            if index == nil then
                return
            end
            if index == 1 then
                for _, v in ipairs(ActiveHighlights) do
                    vim.fn.matchdelete(v.id)
                end
                ActiveHighlights = {}
                return
            end
            vim.fn.matchdelete(ActiveHighlights[index - 1].id)
            table.remove(ActiveHighlights, index - 1)
        end
    )

    -- Call matchadd function on highlight removal menu to provide highlighting preview
    vim.defer_fn(function()
        local win = vim.api.nvim_get_current_win()
        for i, v in ipairs(ActiveHighlights) do
            local match_pattern = PreparePatternForMatch(v.pattern)
            vim.fn.matchadd(v.hl, (i + 1) .. ". " .. match_pattern, 10, -1, { window = win + 1 })
        end
    end, 50)
end

return M