-- Author        : swytch
-- Created       : Friday Mar 12, 2021 21:45:21 CET
-- License       : GPLv3
-- Description   : neovim statusline file
--                 based on github/nihilistkitten's work


local function gen_section(hl_string, items)
    local out = ""
    for _, item in pairs(items) do
        if item ~= "" then
            out = out .. " " .. item
        end
    end
    if out ~= "" then
        return hl_string .. out .. " "
    else
        return out
    end
end

-- sensible names for vim modes
local function get_mode(m)
    local mode_group = {
        ["n"]   = "Normal",
        ["no"]  = "O-Pending",
        ["nov"] = "O-Pending",
        ["noV"] = "O-Pending",
        ["no"] = "O-Pending",
        ["niI"] = "Normal",
        ["niR"] = "Normal",
        ["niV"] = "Normal",
        ["v"]   = "Visual",
        ["V"]   = "V-Line",
        [""]   = "V-Block",
        ["s"]   = "Select",
        ["S"]   = "S-Line",
        [""]   = "S-Block",
        ["i"]   = "Insert",
        ["ic"]  = "Insert",
        ["ix"]  = "Insert",
        ["R"]   = "Replace",
        ["Rc"]  = "Replace",
        ["Rv"]  = "V-Replace",
        ["Rx"]  = "Replace",
        ["c"]   = "Command",
        ["cv"]  = "Ex",
        ["ce"]  = "Ex",
        ["r"]   = "Prompt",
        ["rm"]  = "Prompt",
        ["r?"]  = "Prompt",
        ["!"]   = "Shell",
        ["t"]   = "Terminal",
    }
    return mode_group[m] or "None"
end

local function get_mode_display_name(m)
    local mode = {
        ["Normal"]    = "[ NRM ]",
        ["O-Pending"] = "[ OTR ]",
        ["Visual"]    = "[ VSL ]",
        ["V-Line"]    = "[ V·L ]",
        ["V-Block"]   = "[ V·B ]",
        ["Select"]    = "[ SEL ]",
        ["S-Line"]    = "[ S·L ]",
        ["S-Block"]   = "[ S·B ]",
        ["Insert"]    = "[ INS ]",
        ["Replace"]   = "[ RPL ]",
        ["Command"]   = "[ CMD ]",
        ["Prompt"]    = "[ PMT ]",
        ["Shell"]     = "[ SHL ]",
        ["Terminal"]  = "[ TRM ]",
        ["None"]      = "[ --- ]"
    }
    return mode[m]
end

-- get the highlight group for a mode group
local function get_mode_color(m)
    local color = {
        ["Normal"]    = "%#NormalMode#",
        ["O-Pending"] = "%#NormalMode#",
        ["Visual"]    = "%#VisualMode#",
        ["V-Line"]    = "%#VisualMode#",
        ["V-Block"]   = "%#VisualMode#",
        ["Select"]    = "%#NormalMode#",
        ["S-Line"]    = "%#NormalMode#",
        ["S-Block"]   = "%#NormalMode#",
        ["Insert"]    = "%#InsertMode#",
        ["Replace"]   = "%#ReplaceMode#",
        ["Command"]   = "%#CommandMode#",
        ["Prompt"]    = "%#NormalMode#",
        ["Shell"]     = "%#NormalMode#",
        ["Terminal"]  = "%#NormalMode#",
        ["None"]      = "%#NormalMode#"
    }
    return color[m]
end

-- from https://github.com/nvim-lualine/lualine.nvim/blob/master/lua/lualine/components/filename.lua
local function shorten_path(path, max_len)
    local sep = '/'
    local len = #path
    if len <= max_len then
        return path
    end

    local segments = vim.split(path, sep)
    local start = 1
    if segments[1] == "~" then
        start = start + 1
    end


    for idx = start, #segments - 1 do
        if len <= max_len then
            break
        end

        local segment = segments[idx]
        local short_end = 1
        if (vim.startswith(segment, '.') or vim.startswith(segment, '_')) then
            short_end = 2
        end
        local shortened = segment:sub(1, short_end)
        segments[idx] = shortened
        len = len - (#segment - #shortened)
    end

    if (len > max_len and #segments > 3) then
        while (len > max_len and #segments > 3) do
            table.remove(segments, 2)
        end
        table.insert(segments,2, "...")
    end

    return table.concat(segments, sep)
end

-- from https://github.com/nvim-lua/lsp-status.nvim/blob/master/lua/lsp-status/diagnostics.lua
local function get_lsp_diagnostics()
    local result = {}
    local levels = {
        error = "Error",
        warn = "Warn",
        info = "Info",
        hint = "Hint"
    }

    for k, level in pairs(levels) do
        local count = 0
        local diags = vim.diagnostic.get(0, { severity = level })
        for _, _ in pairs(diags) do
            count = count + 1
        end
        result[k] = count
    end

    return result
end

local function process_diagnostics(prefix, n, hl)
    if n > 0 then
        return hl .. prefix .. n
    else
        return ""
    end
end

local function spell_check()
    if vim.wo.spell then
        local lang = vim.o.spelllang
        return "[SPELL=" .. lang .. "]"
    else
        return ""
    end
end

local function statusline_focused()
    local file = vim.fn.expand("%:p:~")
    local diagnostics = get_lsp_diagnostics()
    local mode = vim.fn.mode()
    local mg = get_mode(mode)
    local accent_color = get_mode_color(mg)
    local winwidth = vim.fn.winwidth(0)

    local left = table.concat {
            gen_section(accent_color, { get_mode_display_name(mg) }),
            gen_section("%#Middle#", { shorten_path(file, winwidth / 2) }),
            gen_section("%#Bottom#", { "%m", "%r" }),
            gen_section(
                "%#Alert#",
                {
                    process_diagnostics(
                        globals.sign_error .. " ",
                        diagnostics.error,
                        "%#DiagnosticVirtualTextError#"
                    ),
                    process_diagnostics(
                        globals.sign_warn .. " ",
                        diagnostics.warn,
                        "%#DiagnosticVirtualTextWarn#"
                    ),
                    process_diagnostics(
                        globals.sign_info .. " ",
                        diagnostics.info,
                        "%#DiagnosticVirtualTextInfo#"
                    )
                }
            )
        }
    local right = table.concat {
            gen_section(
                "%#Bottom#",
                {
                    spell_check(),
                    vim.bo.filetype
                }
            ),
            gen_section("%#Middle#", { "%03.p%%" }),
            gen_section("%#Top#", { "-%03.c-" })
        }

    return table.concat {
            left,
            "%#Statusline#",
            "%=",
            right
        }
end

local function statusline_not_focused()
    local bufnr = vim.fn.winbufnr(vim.g.statusline_winid)
    local file = vim.fn.expand("#" .. bufnr .. ":p:~")
    local winwidth = vim.fn.winwidth(0)
    return table.concat {
            gen_section("%#StatuslineNF#", {
                shorten_path(file, winwidth / 2),
                "%m"
            }),
            "%=",
            gen_section("%#StatuslineNF#", { "%03.p%%" }),
            gen_section("%#StatuslineNF#", { "-%03.c-" })
        }
end

function _G.gen_statusline()
    if vim.g.statusline_winid == vim.fn.win_getid() then
        return statusline_focused()
    else
        return statusline_not_focused()
    end
end

vim.o.statusline = "%!luaeval(\"gen_statusline()\")"