local vim = vim
local symbols = require('symbols')

local D = {}

-- needs plenary
local reload = require('plenary.reload').reload_module

function D.R(name)
    reload(name)
    return require(name)
end

local function setupCommands()
    vim.cmd("command! " .. "DSymbolsOutline " ..
                ":lua require'symbols-outline'.R('symbols-outline').toggle_outline()")
    vim.cmd("command! " .. "SymbolsOutline " ..
                ":lua require'symbols-outline'.toggle_outline()")
end

local function setup_autocmd()
    vim.cmd(
        "autocmd InsertLeave,BufEnter,BufWinEnter,TabEnter,BufWritePost * :lua require('symbols-outline')._refresh()")
    vim.cmd(
        "autocmd CursorHold * :lua require('symbols-outline')._highlight_current_item()")
end

local function getParams()
    return {textDocument = vim.lsp.util.make_text_document_params()}
end

-------------------------
-- STATE
-------------------------
D.state = {
    outline_items = {},
    linear_outline_items = {},
    outline_win = nil,
    outline_buf = nil,
    code_win = nil
}

local function wipe_state()
    D.state = {outline_items = {}, linear_outline_items = {}}
end

-- local markers = {
--     bottom = "└",
--     middle = "├",
--     vertical = "│",
--     horizontal = "─"
-- }

function D.goto_location()
    local current_line = vim.api.nvim_win_get_cursor(D.state.outline_win)[1]
    local node = D.state.linear_outline_items[current_line]
    vim.fn.win_gotoid(D.state.code_win)
    vim.fn.cursor(node.line + 1, node.character + 1)
end

-- parses result into a neat table
local function parse(result, depth)
    local ret = {}
    for _, value in pairs(result) do
        local level = depth or 1
        local children = nil
        if value.children ~= nil then
            children = parse(value.children, level + 1)
        end

        table.insert(ret, {
            deprecated = value.deprecated,
            kind = value.kind,
            icon = symbols.icon_from_kind(value.kind),
            name = value.name,
            detail = value.detail,
            line = value.selectionRange.start.line,
            range_start = value.range.start.line,
            range_end = value.range["end"].line,
            character = value.selectionRange.start.character,
            children = children,
            depth = level
        });
    end
    return ret
end

local function make_linear(outline_items)
    local ret = {}
    for _, value in ipairs(outline_items) do
        table.insert(ret, value)
        if value.children ~= nil then
            local inner = make_linear(value.children)
            for _, value_inner in ipairs(inner) do
                table.insert(ret, value_inner)
            end
        end
    end
    return ret
end

local function highlight_text(name, text, hl_group)
    vim.cmd(string.format("syn match %s /%s/", name, text))
    vim.cmd(string.format("hi def link %s %s", name, hl_group))
end

local function setup_highlights()
    -- -- markers
    -- highlight_text("marker_middle", markers.middle, "Comment")
    -- highlight_text("marker_vertical", markers.vertical, "Comment")
    -- highlight_text("markers_horizontal", markers.horizontal, "Comment")
    -- highlight_text("markers_bottom", markers.bottom, "Comment")

    for _, value in ipairs(symbols.kinds) do
        local symbol = symbols[value]
        highlight_text(value, symbol.icon, symbol.hl)
    end
    vim.cmd('hi FocusedSymbol guibg=#e50050')
end

local function get_lines(outline_items, bufnr, winnr, lines)
    lines = lines or {}
    for _, value in ipairs(outline_items) do
        local line = string.rep("  ", value.depth)
        table.insert(lines, line .. value.icon .. " " .. value.name)

        if value.children ~= nil then
            get_lines(value.children, bufnr, winnr, lines)
        end
    end
    vim.api.nvim_buf_set_keymap(bufnr, "n", "<Cr>",
                                ":lua require('symbols-outline').goto_location()<Cr>",
                                {})
    return lines
end

local function get_details(outline_items, bufnr, winnr, lines)
    lines = lines or {}
    for _, value in ipairs(outline_items) do
        table.insert(lines, value.detail or "")

        if value.children ~= nil then
            get_details(value.children, bufnr, winnr, lines)
        end
    end
    return lines
end

local function write_outline(bufnr, lines)
    vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
end

local function write_details(bufnr, lines)
    for index, value in ipairs(lines) do
        vim.api.nvim_buf_set_virtual_text(bufnr, -1, index - 1,
                                          {{value, "Comment"}}, {})
    end
end

local function disable_nums(winnr)
    vim.api.nvim_win_set_option(winnr, "number", false)
end

local function clear_virt_text(bufnr)
    vim.api.nvim_buf_clear_namespace(bufnr, -1, 0, -1)
end

function D._refresh()
    if D.state.outline_buf ~= nil then
        vim.lsp.buf_request(0, "textDocument/documentSymbol", getParams(),
                            function(_, _, result)

            D.state.code_win = vim.api.nvim_get_current_win()
            D.state.outline_items = parse(result)
            D.state.linear_outline_items = make_linear(parse(result))

            local lines = get_lines(D.state.outline_items, D.state.outline_buf,
                                    D.state.outline_win)
            write_outline(D.state.outline_buf, lines)

            clear_virt_text(D.state.outline_buf)
            local details = get_details(D.state.outline_items,
                                        D.state.outline_buf, D.state.outline_win)
            write_details(D.state.outline_buf, details)
        end)
    end
end

local hovered_hl_ns = vim.api.nvim_create_namespace("hovered_item")

function D._highlight_current_item()

    if D.state.outline_buf == nil or vim.api.nvim_get_current_buf() ==
        D.state.outline_buf then return end

    local hovered_line = vim.api.nvim_win_get_cursor(
                             vim.api.nvim_get_current_win())[1] - 1

    local nodes = {}
    for index, value in ipairs(D.state.linear_outline_items) do
        if value.line == hovered_line or (hovered_line > value.range_start and hovered_line < value.range_end) then
            value.line_in_outline = index
            table.insert(nodes, value)
        end
    end

    -- clear old highlight
    vim.api.nvim_buf_clear_namespace(D.state.outline_buf, hovered_hl_ns, 0, -1)
    for _, value in ipairs(nodes) do
        vim.api.nvim_buf_add_highlight(D.state.outline_buf, hovered_hl_ns,
                                       "FocusedSymbol",
                                       value.line_in_outline - 1,
                                       value.depth * 2, -1)
        vim.api.nvim_win_set_cursor(D.state.outline_win,
                                    {value.line_in_outline, 1})
    end
end

local function setup_keymaps(bufnr)
    -- goto_location of symbol
    vim.api.nvim_buf_set_keymap(bufnr, "n", "<Cr>",
                                ":lua require('symbols-outline').goto_location()<Cr>",
                                {})
    -- close outline when escape is pressed
    vim.api.nvim_buf_set_keymap(bufnr, "n", "<Esc>",
                                ":bw!<Cr>",
                                {})
end

local function handler(_, _, result)
    D.state.code_win = vim.api.nvim_get_current_win()

    if D.state.outline_buf == nil then
        D.state.outline_buf = vim.api.nvim_create_buf(false, true)
        vim.api.nvim_buf_attach(D.state.outline_buf, false,
                                {on_detach = function(_, _) wipe_state() end})
        vim.api.nvim_buf_set_option(D.state.outline_buf, "bufhidden", "delete")

        local current_win = vim.api.nvim_get_current_win()
        local current_win_width = vim.api.nvim_win_get_width(current_win)

        vim.cmd("vsplit")
        vim.cmd("vertical resize " .. math.ceil(current_win_width * 0.25))
        D.state.outline_win = vim.api.nvim_get_current_win()
        vim.api.nvim_win_set_buf(D.state.outline_win, D.state.outline_buf)

        D.state.outline_items = parse(result)
        D.state.linear_outline_items = make_linear(parse(result))

        disable_nums(D.state.outline_win)

        local lines = get_lines(D.state.outline_items, D.state.outline_buf,
                                D.state.outline_win)
        write_outline(D.state.outline_buf, lines)

        local details = get_details(D.state.outline_items, D.state.outline_buf,
                                    D.state.outline_win)
        write_details(D.state.outline_buf, details)

        setup_keymaps(D.state.outline_buf)
        setup_highlights()
    else
        vim.api.nvim_win_close(D.state.outline_win, true)
    end
end

function D.toggle_outline()
    vim.lsp.buf_request(0, "textDocument/documentSymbol", getParams(), handler)
end

function D.setup()
    setupCommands()
    setup_autocmd()
end

return D