local function parseValueSimily(vm, source, lsp)
    local key = source[1]
    if not key then
        return nil
    end
    local positions = {}
    vm:eachSource(function (other)
        if other == source then
            return
        end
        if      other[1] == key
            and not other:bindLocal()
            and other:bindValue()
            and other:action() == 'set'
            and source:bindValue() ~= other:bindValue()
        then
            positions[#positions+1] = {
                other.start,
                other.finish,
            }
        end
    end)
    if #positions == 0 then
        return nil
    end
    return positions
end

local function parseValueCrossFile(vm, source, lsp)
    local value = source:bindValue()
    local positions = {}
    value:eachInfo(function (info, src)
        if info.type == 'local' and src.uri == value.uri then
            positions[#positions+1] = {
                src.start,
                src.finish,
                value.uri,
            }
            return true
        end
    end)
    if #positions > 0 then
        return positions
    end

    value:eachInfo(function (info, src)
        if info.type == 'set' and src.uri == value.uri  then
            positions[#positions+1] = {
                src.start,
                src.finish,
                value.uri,
            }
        end
    end)
    if #positions > 0 then
        return positions
    end

    value:eachInfo(function (info, src)
        if info.type == 'return' and src.uri == value.uri then
            positions[#positions+1] = {
                src.start,
                src.finish,
                value.uri,
            }
        end
    end)
    if #positions > 0 then
        return positions
    end

    local destVM = lsp:getVM(value.uri)
    if not destVM then
        positions[#positions+1] = {
            0, 0, value.uri,
        }
        return positions
    end

    local result = parseValueSimily(destVM, source, lsp)
    if result then
        for _, position in ipairs(result) do
            positions[#positions+1] = position
            position[3] = value.uri
        end
    end
    if #positions > 0 then
        return positions
    end

    return positions
end

local function parseValue(vm, source, lsp)
    local positions = {}
    local mark = {}

    local function callback(src)
        if source == src then
            return
        end
        if mark[src] then
            return
        end
        mark[src] = true
        if src.start == 0 then
            return
        end
        local uri = src.uri
        if uri == '' then
            uri = nil
        end
        positions[#positions+1] = {
            src.start,
            src.finish,
            uri,
        }
    end

    if source:bindValue() then
        source:bindValue():eachInfo(function (info, src)
            if info.type == 'set' or info.type == 'local' or info.type == 'return' then
                callback(src)
                return true
            end
        end)
    end
    local parent = source:get 'parent'
    if parent then
        parent:eachInfo(function (info, src)
            if info[1] == source[1] then
                if info.type == 'set child' then
                    callback(src)
                end
            end
        end)
    end
    if #positions == 0 then
        return nil
    end
    return positions
end

local function parseLabel(vm, label, lsp)
    local positions = {}
    label:eachInfo(function (info, src)
        if info.type == 'set' then
            positions[#positions+1] = {
                src.start,
                src.finish,
            }
        end
    end)
    if #positions == 0 then
        return nil
    end
    return positions
end

local function jumpUri(vm, source, lsp)
    local uri = source:get 'target uri'
    local positions = {}
    positions[#positions+1] = {
        0, 0, uri,
    }
    return positions
end

local function parseClass(vm, source)
    local className = source:get 'emmy class'
    local positions = {}
    vm.emmyMgr:eachClass(className, function (class)
        local src = class:getSource()
        positions[#positions+1] = {
            src.start,
            src.finish,
            src.uri,
        }
    end)
    return positions
end

return function (vm, source, lsp)
    if not source then
        return nil
    end
    if source:bindValue() then
        return parseValue(vm, source, lsp)
            or parseValueSimily(vm, source, lsp)
    end
    if source:bindLabel() then
        return parseLabel(vm, source:bindLabel(), lsp)
    end
    if source:get 'target uri' then
        return jumpUri(vm, source, lsp)
    end
    if source:get 'in index' then
        return parseValue(vm, source, lsp)
            or parseValueSimily(vm, source, lsp)
    end
    if source:get 'emmy class' then
        return parseClass(vm, source)
    end
end