local findResult = require 'matcher.find_result'
local hover = require 'matcher.hover'

local CompletionItemKind = {
    Text = 1,
    Method = 2,
    Function = 3,
    Constructor = 4,
    Field = 5,
    Variable = 6,
    Class = 7,
    Interface = 8,
    Module = 9,
    Property = 10,
    Unit = 11,
    Value = 12,
    Enum = 13,
    Keyword = 14,
    Snippet = 15,
    Color = 16,
    File = 17,
    Reference = 18,
    Folder = 19,
    EnumMember = 20,
    Constant = 21,
    Struct = 22,
    Event = 23,
    Operator = 24,
    TypeParameter = 25,
}

local function matchKey(me, other)
    if me == other then
        return false
    end
    if me == '' then
        return true
    end
    if #me > #other then
        return false
    end
    local lMe = me:lower()
    local lOther = other:lower()
    if lMe:sub(1, 1) ~= lOther:sub(1, 1) then
        return false
    end
    if lMe == lOther:sub(1, #lMe) then
        return true
    end
    local used = {
        [1] = true,
    }
    local cur = 2
    local lookup
    local researched
    for i = 2, #lMe do
        local c = lMe:sub(i, i)
        -- 1. 看当前字符是否匹配
        if c == lOther:sub(cur, cur) then
            used[cur] = true
            goto NEXT
        end
        -- 2. 看前一个字符是否匹配
        if not used[cur-1] then
            if c == lOther:sub(cur-1, cur-1) then
                used[cur-1] = true
                goto NEXT
            end
        end
        -- 3. 向后找这个字
        lookup = lOther:find(c, cur+1, true)
        if lookup then
            cur = lookup
            used[cur] = true
            goto NEXT
        end

        -- 4. 重新搜索整个字符串，但是只允许1次，否则失败.如果找不到也失败
        if researched then
            return false
        else
            researched = true
            for j = 2, cur - 2 do
                if c == lOther:sub(j, j) then
                    used[j] = true
                    goto NEXT
                end
            end
            return false
        end
        -- 5. 找到下一个可用的字，如果超出长度就算成功
        ::NEXT::
        repeat
            cur = cur + 1
        until not used[cur]
        if cur > #lOther then
            break
        end
    end
    return true
end

local function searchLocals(vm, pos, name, callback)
    for _, loc in ipairs(vm.results.locals) do
        if loc.source.start == 0 then
            goto CONTINUE
        end
        if loc.source.start <= pos and loc.close >= pos then
            if matchKey(name, loc.key) then
                callback(loc)
            end
        end
        ::CONTINUE::
    end
end

local function searchFields(name, parent, object, callback)
    if not parent or not parent.value or not parent.value.child then
        return
    end
    for key, field in pairs(parent.value.child) do
        if type(key) ~= 'string' then
            goto CONTINUE
        end
        if object then
            if not field.value or field.value.type ~= 'function' then
                goto CONTINUE
            end
        end
        if matchKey(name, key) then
            callback(field)
        end
        ::CONTINUE::
    end
end

local KEYS = {'and', 'break', 'do', 'else', 'elseif', 'end', 'false', 'for', 'function', 'goto', 'if', 'in', 'local', 'nil', 'not', 'or', 'repeat', 'return', 'then', 'true', 'until', 'while', 'toclose'}
local function searchKeyWords(name, callback)
    for _, key in ipairs(KEYS) do
        if matchKey(name, key) then
            callback(key)
        end
    end
end

local function getKind(var, default)
    local value = var.value
    if default == CompletionItemKind.Variable then
        if value.type == 'function' then
            return CompletionItemKind.Function
        end
    end
    if default == CompletionItemKind.Field then
        local tp = type(value.value)
        if tp == 'number' or tp == 'integer' or tp == 'string' then
            return CompletionItemKind.Enum
        end
        if value.type == 'function' then
            if var.parent and var.parent.value and var.parent.value.ENV ~= true then
                return CompletionItemKind.Method
            else
                return CompletionItemKind.Function
            end
        end
    end
    return default
end

local function getDetail(var)
    local tp = type(var.value.value)
    if tp == 'boolean' then
        return ('= %q'):format(var.value.value)
    elseif tp == 'number' then
        if math.type(var.value.value) == 'integer' then
            return ('= %q'):format(var.value.value)
        else
            local str = ('= %.10f'):format(var.value.value)
            local dot = str:find('.', 1, true)
            local suffix = str:find('[0]+$', dot+2)
            if suffix then
                return str:sub(1, suffix-1)
            else
                return str
            end
        end
    elseif tp == 'string' then
        return ('= %q'):format(var.value.value)
    end
    return nil
end

local function getDocument(var, source)
    if var.value.type == 'function' then
        return {
            kind = 'markdown',
            value = hover(var, source),
        }
    end
    return nil
end

local function searchAsGlobal(vm, pos, result, callback)
    searchLocals(vm, pos, result.key, function (var)
        callback(var, CompletionItemKind.Variable)
    end)
    searchFields(result.key, vm.results.locals[1], nil, function (var)
        callback(var, CompletionItemKind.Field)
    end)
    searchKeyWords(result.key, function (name)
        callback(name, CompletionItemKind.Keyword)
    end)
end

local function searchAsSuffix(result, callback)
    searchFields(result.key, result.parent, result.source.object, function (var)
        callback(var, CompletionItemKind.Field)
    end)
end

return function (vm, pos)
    local result, source = findResult(vm, pos, true)
    if not result then
        return nil
    end

    local list = {}
    local mark = {}
    local function callback(var, defualt)
        local key
        if type(var) == 'string' then
            key = var
        else
            key = var.key
        end
        if mark[key] then
            return
        end
        mark[key] = true
        if var == key then
            list[#list+1] = {
                label = key,
                kind = defualt,
            }
        else
            list[#list+1] = {
                label = var.key,
                kind = getKind(var, defualt),
                detail = getDetail(var),
                documentation = getDocument(var, source),
            }
        end
    end

    if result.type == 'local' then
        searchAsGlobal(vm, pos, result, callback)
    elseif result.type == 'field' then
        if result.parent and result.parent.value and result.parent.value.ENV == true then
            searchAsGlobal(vm, pos, result, callback)
        else
            searchAsSuffix(result, callback)
        end
    end
    return list
end