add message database thing

1 files changed, 116 insertions, 0 deletions

diff --git a/messagelog.lua b/messagelog.lua
new file mode 100644
index 0000000..9f05ab4
--- /dev/null
+++ b/messagelog.lua
@@ -0,0 +1,116 @@
+local function esc(x)
+    local res = ""
+    for i=1, #x do
+        local c = x:sub(i,i)
+        if c == "\\" then
+            res = res .. "\\\\"
+        elseif c == "\01" then
+            res = res .. "\\a"
+        elseif c == "\02" then
+            res = res .. "\\b"
+        elseif c == "|" then
+            res = res .. "\\p"
+        else
+            res = res .. c
+        end
+    end
+    return res
+end
+
+local function unesc(x)
+    local res = ""
+    local i = 1
+    while i <= #x do
+        local c = x:sub(i,i)
+        if c == "\\" then
+            local c2 = x:sub(i+1,i+1)
+            if c2 == "\\" then res = res .. "\\" end
+            if c2 == "a" then res = res .. "\01" end
+            if c2 == "b" then res = res .. "\01" end
+            if c2 == "p" then res = res .. "|" end
+            i = i + 1
+        else
+            res = res .. c
+        end
+        i = i + 1
+    end
+    return res
+end
+
+local function genmsg(msg)
+    return "\01|"..msg.timestamp.."|"..esc(msg.sender).."|"..esc(msg.content).."|"..(msg.parent or "").."|"
+end
+
+local function parsemsg(readable)
+    if readable:read(1) ~= "\01" or readable:read(1) ~= "|" then
+        return false
+    end
+    local section = 0
+    local timestamp = ""
+    local sender = ""
+    local content = ""
+    local parent = ""
+    while true do
+        local c = readable:read(1)
+        if c == nil then
+            return false
+        end
+        if c == "|" then
+            section = section + 1
+            if section == 4 then return {timestamp=timestamp, sender=unesc(sender), content=unesc(content), parent=parent=="" and nil or tonumber(parent)} end
+        elseif section == 0 then
+            timestamp = timestamp .. c
+        elseif section == 1 then
+            sender = sender .. c
+        elseif section == 2 then
+            content = content .. c
+        else
+            parent = parent .. c
+        end
+    end
+end
+
+local function appendmsg(filename,msg)
+    local f = io.open(filename,"ab")
+    local res = f:seek("cur",0)
+    f:write(genmsg(msg))
+    f:close()
+    return res
+end
+
+local function getmsg(filename,id)
+    local f = io.open(filename,"rb")
+    f:seek("set",id)
+    local msg = parsemsg(f)
+    msg.id = id
+    f:close()
+    return msg
+end
+
+local function last_n(filename,n,id)
+    local res = {}
+    local f = io.open(filename,"rb")
+    local i = id or 0
+    while true do
+        i = i - 1
+        local pos = f:seek(id and "set" or "end",i)
+        local c = f:read(1)
+        if not c then
+            local res2 = {}
+            for i=#res,1,-1 do
+                table.insert(res2,res[i])
+            end
+            return res2
+        end
+        if c == "\01" then table.insert(res, getmsg(filename,pos)) end
+        if #res >= n or pos == 0 then
+            local res2 = {}
+            for i=#res,1,-1 do
+                table.insert(res2,res[i])
+            end
+            return res2
+        end
+    end
+end
+
+return {last_n = last_n, getmsg = getmsg, appendmsg = appendmsg}
\ No newline at end of file