os = require "os"
socket = require "socket"


------------------------------------------------------------------------------
-- config and handling                                                      --
------------------------------------------------------------------------------

function shortname()
    --
    -- Short hostname
    --
    local long = socket.dns.gethostname()
    return string.gmatch(long, '[^.]+')()
end

function file_exists(name)
    --
    -- True if file *name* exists
    --
    local f = io.open(name,"r")
    if f ~= nil then
        io.close(f)
        return true
    else
        return false
    end
end

function init_host(session)
    --
    -- Do host-specific init, if exists
    --
    local init = session.dirs.host .. "/init.lua"
    if file_exists(init) then
        dofile(init)
        return
    end
end

function handle(session)
    --
    -- Look for action handler in session dirs; do first one that exists
    --
    local valid = {
        newmail = true,
        rewind = true,
        cleanup = true,
        migrate = true
    }
    if not valid[session.action] then
        error("invalid action: " .. session.action)
        return nil
    end
    init_host(session)
    for k,v in ipairs({session.dirs.host, session.dirs.default}) do
        attempt = v .. "/handlers/" .. session.action .. ".lua"
        if file_exists(attempt) then
            dofile(attempt)
            return
        end
    end
end


------------------------------------------------------------------------------
-- mail getters                                                             --
------------------------------------------------------------------------------

function get_queue(acct, mbox)
    --
    -- Get queue from *mbox* from *acct* or nil (no messages)
    --
    -- If mbox is not specified, "FILTER_QUEUE" is used
    --
    mbox = mbox or "FILTER_QUEUE"
    local exist, unread, unseen, uidnext = acct[mbox]:check_status()
    if exist > 0 then
        return acct[mbox]:select_all()
    end
    return nil
end

function _notifirc1(subj, from, body)
    --
    -- notify about message using (pre-configured) notifirc
    --
    local fd = assert(io.popen('notifirc -c mail -f - "message preview:"', "w"))
    local fmt = "> %s\n> %s\n> BODY: %s"
    fd:write(fmt:format(subj, from, body))
    fd:close()
end

function notifirc_all(seq)
    --
    -- Send notifications about all messages in *seq*
    --
    for _, mesg in ipairs(seq) do
        mbox, uid = table.unpack(mesg)
        subj = mbox[uid]:fetch_field('Subject')
        from = mbox[uid]:fetch_field('From')
        body = mbox[uid]:fetch_body()
        _notifirc1(subj, from, body)
    end
end

function _partinf_compare(a, b)
    if not type(a) == type(b) then
        return false
    end
    if type(a) == 'number' then
        return a == b
    elseif type(a) == 'string' then
        return a:lower() == b:lower()
    end
end

function has_part_like(query, structure)
    --
    -- True if structure has MIME part matching *query*
    --
    if structure == nil then
        return false
    end
    for partid, partinf in pairs(structure) do
        local part_answer = true
        -- check all query parts
        for qkey, qvalue in pairs(query) do
            value = partinf[qkey]
            if not _partinf_compare(value, qvalue) then
                part_answer = false
                break
            end
        end
        if part_answer then
            return true
        end
    end
    return false
end

function save_header(mesg, name)
    --
    -- Append header from *mesg* to file named *name*
    --
    -- File will be placed under directory specified by IMAPDOMO_HEADERS
    -- environment variable.
    --
    local dest = os.getenv("IMAPDOMO_HEADERS") .. '/' .. name
    local cmd = ('cat >>"%q"'):format(dest)
    mbox, uid = table.unpack(mesg)
    header = mbox[uid]:fetch_header()
    if pipe_to(cmd, header) == 0 then
        return true
    else
        return false
    end
end

function filter_header_saved(seq, name)
    --
    -- Save headers from sequence
    --
    -- Append header of each message in sequence *seq* to file names
    -- *name* and return new sequence with those messages where save was
    -- successful.
    --
    result = Set {}
    for _, mesg in ipairs(seq) do
        if save_header(mesg, name) then
            table.insert(result, mesg)
        end
    end
    return result
end

function filter_part_like(query, seq)
    --
    -- Run MIME part query on *seq* sequence of messages
    --
    result = Set {}
    for _, mesg in ipairs(seq) do
        mbox, uid = table.unpack(mesg)
        structure = mbox[uid]:fetch_structure()
        if has_part_like(query, structure) then
            table.insert(result, mesg)
        end
    end
    return result
end