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

local function searchAsArg(vm, inCall, inString, callback)
    local special = inCall.func.lib and inCall.func.lib.special
    if not special then
        return
    end
    if special == 'require' then
        if not vm.lsp or not vm.lsp.workspace then
            return
        end
        local results = vm.lsp.workspace:matchPath(vm.uri, inString[1])
        if not results then
            return
        end
        for _, v in ipairs(results) do
            if v ~= inString[1] then
                callback(v, CompletionItemKind.Module)
            end
        end
    end
end

local function findClosePos(vm, pos)
    local curDis = math.maxinteger
    local parent = nil
    for sources, object in pairs(vm.results.sources) do
        if sources.type == 'multi-source' then
            for _, source in ipairs(sources) do
                if source.type ~= 'simple' then
                    local dis = pos - source.finish
                    if dis > 0 and dis < curDis then
                        curDis = dis
                        parent = object
                    end
                end
            end
        else
            local source = sources
            if source.type ~= 'simple' then
                local dis = pos - source.finish
                if dis > 0 and dis < curDis then
                    curDis = dis
                    parent = object
                end
            end
        end
    end
    if parent and parent.type ~= 'local' and parent.type ~= 'field' then
        parent = nil
    end
    if parent then
        -- 造个假的 DirtyName
        local source = {
            type = 'name',
            start = pos,
            finish = pos,
            [1]    = '',
        }
        local result = {
            type = 'field',
            parent = parent,
            key = '',
            source = source,
        }
        return result, source
    end
    return nil
end

local function isContainPos(obj, pos)
    if obj.start <= pos and obj.finish + 1 >= pos then
        return true
    end
    return false
end

local function getString(vm, pos)
    for _, source in ipairs(vm.results.strings) do
        if isContainPos(source, pos) then
            return source
        end
    end
    return nil
end

local function findArgCount(args, pos)
    for i, arg in ipairs(args) do
        if isContainPos(arg, pos) then
            return i, arg
        end
    end
    return #args + 1, nil
end

-- 找出范围包含pos的call
local function findCall(vm, pos)
    local results = {}
    for _, call in ipairs(vm.results.calls) do
        if isContainPos(call.args, pos) then
            local n, arg = findArgCount(call.args, pos)
            if arg and arg.type ~= 'string' then
                return nil
            end
            local var = vm.results.sources[call.lastObj]
            if var then
                results[#results+1] = {
                    func = call.func,
                    var = var,
                    source = call.lastObj,
                    select = n,
                    args = call.args,
                }
            end
        end
    end
    if #results == 0 then
        return nil
    end
    -- 可能处于 'func1(func2(' 的嵌套中，因此距离越远的函数层级越低
    table.sort(results, function (a, b)
        return a.args.start < b.args.start
    end)
    return results
end

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

    inString = getString(vm, pos)
    if inString then
        local calls = findCall(vm, pos)
        if not calls then
            return nil
        end
        inCall = calls[#calls]
    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 inCall then
        searchAsArg(vm, inCall, inString, callback)
    else
        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
    end
    if #list == 0 then
        return nil
    end
    return list
end