--[[ Deposit module.

This module takes care of the complete deposit process (except for the back
end storage, which is called here but defined in the repo module).

The deposit process is carried out in several steps:

- SIP generation (`generate_sip()`): scans the laundry list CSV and builds a
  temporary data structure with the found metadata; generates unique IDs for
  resources; infers some implicit relationships from the position of the CSV
  rows and folder layout; adds system-controlled metadata.
- File staging (`deposit()`): scan through the generated SIP, identifies the
  files, calculates their checksums, and moves them to temporary storage; adds
  checksums to the metadata. TODO allow user-provided metadata and validation
- Graph generation: generate an RDF graph for each resource in the SIP.
- Permanent storage: push the RDF graph to permanent store (via functions in
  the `repo` module), which includes content model validation; if this
  succeeds, related files are also moved from the staging area to the archival
  store.
- Cleanup (optional): if requested, the laundry list and resource folder are
  deleted from their original location.

--]]
local io = io

local csv = require "ftcsv"
local dir = require "pl.dir"
local file = require "pl.file"
local libmagic = require "libmagic"
local path = require "pl.path"
local pp = require "pl.pretty"

local term = require "volksdata.term"
local triple = require "volksdata.triple"
local graph = require "volksdata.graph"

local pkar = require "pocket_archive"
local model = require "pocket_archive.model"
local mc = require "pocket_archive.monocypher"
local repo = require "pocket_archive.repo"
local validator = require "pocket_archive.validator"

local logger = pkar.logger
local dbg = require "debugger"

-- "nil" table - for missing key fallback in chaining.
local NT = {}

-- Local path to URI mapping. For linking between newly created resources.
local path_to_uri


-- Initialize libmagic database.
local magic = libmagic.open(libmagic.MIME_TYPE, libmagic.NO_CHECK_COMPRESS )
assert(magic:load())


-- For idgen(). Makes a 60-character pool with ~5.9 bits of entropy per char.
local chpool = {}
for i = 48, 57  do table.insert(chpool, i) end  -- 0-9
for i = 65, 90  do table.insert(chpool, i) end  -- A-Z
for i = 97, 122 do table.insert(chpool, i) end  -- a-z


--[[
Generate a random, reader-friendly ID.

A 16-character ID with the above defined #chpool of 60 smybols has an entropy
of 94.5 bits, which should be plenty for a medium-sized repository.
]]
local function idgen(len)
    local charlist = {}
    for i = 1, (len or pkar.config.id.len) do
        table.insert(charlist, string.char(chpool[math.random(1, #chpool)]))
    end

    return table.concat(charlist)
end


local function generate_sip(ll_path)
    local sip = {root_path = path.dirname(ll_path)}
    path_to_uri = {}

    local tn_dir = path.join(sip.root_path, "proc", "tn")
    dir.makepath(tn_dir)

    local prev_path

    local i = 0
    for row_n, row in csv.parseLine(ll_path) do
        local has_content
        for k, v in pairs(row) do
            -- Change "" to nil.
            if v == "" then row[k] = nil
            else has_content = true end
        end
        -- Skip empty lines.
        if not has_content then goto skip end

        logger:debug("Row path: ", row.source_path or "")
        logger:debug("Parsing row:", pp.write(row))
        if row.source_path then
            i = i + 1
            logger:info(
                    ("Processing LL resource #%d at row #%d.")
                    :format(i, row_n))
            prev_path = row.source_path
            -- New row.
            sip[i] = {id = "par:" .. idgen()}
            -- Add to path to URI map for later referencing.
            path_to_uri[row.source_path] = sip[i].id
            for k, v in pairs(row) do
                if not v then goto cont1 end  -- skip empty strings.
                if pkar.config.md.single_values[k] then sip[i][k] = v
                -- Multi-values are ordered in the SIP for further processing.
                else sip[i][k] = {v} end
                ::cont1::
            end
        else
            -- Continuation of values from a previous row.
            if i < 1 then
                error("First row MUST have a path value.", 2)
            elseif not prev_path then
                error(("No path information at row %d"):format(i), 2)
            else
                for k, v in pairs(row) do
                    if not v then goto cont2 end  -- skip empty strings.
                    if pkar.config.md.single_values[k] then
                        -- It doesn't make much sense to overwrite, maybe throw an error?
                        error(
                            ("On CSV row #%d: field %s is single-valued.")
                            :format(row_n, k))
                    else
                        logger:debug("Value: ", v)
                        logger:debug("Inserting at row ", i - 1)
                        table.insert(sip[i][k], v)
                    end
                    ::cont2::
                end
                row.source_path = prev_path
            end
        end
        ::skip::
        row_n = row_n + 1
    end
    -- Infer structure from paths and row ordering.
    for i, v in ipairs(sip) do
        local rmod = model.types[v.content_type]
        dbg.assert(v.source_path)
        local fpath = path.join(sip.root_path, v.source_path)
        --dbg.assert(rmod)
        v.has_member = v.has_member or {}
        -- Create implicit members from single-file artifact.
        if rmod.types.artifact and path.isfile(fpath) then
            local file_id = "par:" .. idgen()
            -- Insert file resource and move it into a new sub-folder.
            table.insert(sip, {
                content_type = rmod.default_fmodel or "file",
                id = file_id,
                label = path.basename(v.source_path),
                source_path = v.source_path,
            })
            sip[i].has_file = file_id
            sip[i].pref_rep = file_id
            sip[i].source_path = nil
            goto skip
        end
        for j = i + 1, #sip do
            if sip[j].source_path:match("^" .. pkar.escape_ptn(v.source_path))
            then
                local rel_path = sip[j].source_path:sub(#v.source_path + 2)
                logger:debug("rel_path: " .. rel_path)
                if not rel_path:match("/") then
                    logger:debug(("Adding member %s to %s"):format(
                            rel_path, v.source_path))
                    table.insert(v.has_member, sip[j].id)
                end
            end
        end
        ::skip::
    end

    return sip
end


--[[  Convert a SIP resource table to an in-memory Volksdata graph.

--]]
local function rsrc_to_graph(rsrc)
    local rmod = model.types[rsrc.content_type]
    logger:info("Updating resource md: ", pp.write(rsrc))

    local s = term.new_iriref_ns(rsrc.id)
    local gr = graph.new(nil)

    it = gr:add_init()
    for prop, v in pairs(rsrc) do
        if prop == "id" then goto skip end
        logger:debug(("Adding attribute: %s = %s"):format(prop, pp.write(v)))
        local p = model.id_to_uri[prop]
        if not p then
            logger:warn(
                ("Term %s has no URI mapped. Assigning `pas:%s`.")
                :format(prop, prop))
            p = term.new_iriref_ns("pas:" .. prop)
        end
        local pconf = (rmod.properties or NT)[prop] or NT
        local rdf_type_str = pkar.config.md.datatypes[pconf.type]
        local rdf_type
        if rdf_type_str then
            rdf_type = term.new_iriref_ns(rdf_type_str).data
        end
        -- Force all fields to be multi-valued.
        if type(v) ~= "table" then v = {v} end

        -- Convert values to URIs.
        local o
        --if prop == "has_member" then dbg() end
        for i, vv in ipairs(v) do
            if prop == "content_type" then
                o = term.new_iriref_ns(rmod.uri)
            elseif pconf.type == "resource" then
                if not vv:match("^[a-z]*:") then
                    -- Convert local path to URIs.
                    v[i] = assert(path_to_uri[vv]) end
                o = term.new_iriref_ns(v[i])
            elseif pconf.type == "ext_resource" then
                o = term.new_iriref(vv)
            else o = term.new_lit(vv, rdf_type) end
            it:add_iter(triple.new(s, p, o))
        end

        -- Create implicit bricks for "has_member" property.
        if prop == "has_member" then
            local proxy_s
            for i, vv in ipairs(v) do
                -- Add linked list proxies.
                local brick_uri = term.new_iriref_ns("par:" .. idgen())
                if i == 1 then
                    proxy_s = s
                    it:add_iter(triple.new(
                            proxy_s, model.id_to_uri.first, brick_uri))

                    -- Add the "has member" property.
                    it:add_iter(triple.new(
                        s,
                        term.new_iriref_ns(pconf.uri),
                        term.new_iriref_ns(vv)))
                else
                    it:add_iter(triple.new(proxy_s, model.id_to_uri.next, brick_uri))
                end
                -- Add the reference.
                -- Add basic triples.
                for t in pairs(model.types.brick.types) do
                    it:add_iter(triple.new(
                        brick_uri,
                        pkar.RDF_TYPE,
                        model.id_to_uri[t]
                    ))
                end
                it:add_iter(triple.new(
                    brick_uri,
                    model.id_to_uri.content_type,
                    term.new_iriref_ns("pas:Brick")))
                -- Add reference.
                it:add_iter(triple.new(
                    brick_uri,
                    term.new_iriref_ns("pas:ref"),
                    term.new_iriref_ns(vv)))
                proxy_s = brick_uri
            end

            goto skip
        end
        ::skip::
    end
    for i, m in ipairs(rmod.lineage) do
        it:add_iter(triple.new(
            s, pkar.RDF_TYPE,
            term.new_iriref_ns(model.types[m].uri)))
    end
    it:add_done()

    return gr, s
end


-- Submission module.
local M = {}


M.deposit = function(ll_path, cleanup)
    local sip = generate_sip(ll_path)

    for i, rsrc in ipairs(sip) do
        -- TODO Wrap this chunk into a txn. Each row is atomic.
        logger:debug(("Processing resource #%d of %d: %s"):format(
                i, #sip, rsrc.id))

        local in_path, fext
        if not rsrc.source_path then goto continue end

        in_path = path.join(sip.root_path, rsrc.source_path)
        fext = path.extension(in_path)
        -- If it's a directory, skip file processing.
        if not path.isfile(in_path) then goto continue end

        do
            local tmp_dir = path.join(pkar.config.fs.ores_path, "tmp/")
            local file_ext
            _, file_ext = path.splitext(in_path)
            local tmp_path = tmp_dir .. rsrc.id .. file_ext
            dir.makepath(tmp_dir)

            local ifh = assert(io.open(in_path, "r"))

            rsrc.format = {magic:filehandle(ifh)}
            local hash_it = mc.new_blake2b()
            local fsize = 0
            logger:debug("Hashing ", in_path)
            local ofh = assert(io.open(tmp_path, "w"))
            while true do
                chunk = ifh:read(pkar.config.fs.stream_chunk_size)
                if not chunk then break end
                hash_it:update(chunk)
                ofh:write(chunk)
                fsize = fsize + #chunk
            end
            local checksum = hash_it:final(true)
            rsrc.checksum = {"urn:blake2:" .. checksum}
            rsrc.size = fsize

            ofh:close()
            ifh:close()

            -- Copy file and calculate checksum.
            local out_dir, out_path
            out_dir = path.join(
                    pkar.config.fs.ores_path,
                    checksum:sub(1, 2),
                    checksum:sub(3, 4))
            out_path = path.join(out_dir, checksum:sub(1,32) .. fext)
            dir.makepath(out_dir)
            logger:debug(("Moving file %s to %s"):format(tmp_path, out_path))
            dir.movefile(tmp_path, out_path)
            rsrc.archive_path = out_path

            -- Copy thumbnail if existing.
            if rsrc.thumbnail then
                src_path = rsrc.thumbnail
                out_path = path.join(
                        out_dir, path.basename(src_path))
                logger:debug(("Moving file %s to %s"):format(src_path, out_path))
                dir.movefile(src_path, out_path)
                rsrc.thumbnail = out_path
            end
        end

        ::continue::

        tstamp = os.date("!%Y-%m-%dT%TZ")
        rsrc.submitted = tstamp
        rsrc.last_modified = tstamp

        local tmp_gr, s
        tmp_gr, s = rsrc_to_graph(rsrc)

        local val_report = validator.validate(tmp_gr, s)
        if val_report.max_level == "ERROR" then error(
            "Validation raised errors: " .. pp.write(val_report))
        elseif val_report.max_level == "WARN" then logger:warn(
            "Validation raised warnings: " .. pp.write(val_report))
        elseif val_report.max_level == "NOTICE" then logger:warn(
            "Validation raised notices: " .. pp.write(val_report)) end

        repo.store_updates(tmp_gr, s)
    end

    -- Remove processing directory.
    dir.rmtree(path.join(sip.root_path, "proc"))

    if cleanup then
        -- Gather all top-level directories and delete them.
        rsrc_paths = {}
        for i, rsrc in ipairs(sip) do
            rsrc_paths[rsrc.source_path:match("[^/]+")] = true
        end
        for tlf in pairs(rsrc_paths) do
            local target = path.join(sip.root_path, tlf)
            logger:info("Cleaning up: " .. target)
            if path.isdir(target) then dir.rmtree(target)
            elseif path.isfile(target) then file.delete(target) end
        end
        logger:info("Cleaning up: " .. ll_path)
        file.delete(ll_path)
    end
end


return M