-- only lmt because the backend code doesn't deal with it and it makes
-- no sense to waste time on that for mkiv

if not modules then modules = { } end modules ['data-hsh'] = {
    version   = 0.002,
    comment   = "companion to luat-lib.mkiv",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

-- todo: options
--
-- lowercase
-- cleanupnames (normalize)
-- use database from project tree

local type = type
local gsub = string.gsub
local addsuffix, basename, pathpart, filesuffix, filesize = file.addsuffix, file.basename, file.pathpart, file.suffix, file.size
local loadtable, savetable = table.load, table.save
local loaddata, savedata, open = io.loaddata, io.savedata, io.open

local trace_hashed  = false
local report_hashed = logs.reporter("resolvers","hashed")

trackers.register("resolvers.locating", function(v) trace_hashed = v end)
trackers.register("resolvers.hashed",   function(v) trace_hashed = v end)

-- we can have a virtual file: open at the position, make sure read and seek don't
-- go beyond the boundaries

local resolvers = resolvers
local finders   = resolvers.finders
local openers   = resolvers.openers
local loaders   = resolvers.loaders

local ordered = { }
local hashed  = { }
local version = 0.002

-- local lowercase = characters.lower

local function showstatus(database,metadata)
    report_hashed("database %a, %i paths, %i names, %i unique blobs, %i compressed blobs",
        database, metadata.nofpaths, metadata.nofnames, metadata.nofblobs, metadata.nofcompressed
    )
end

local function validhashed(database)
    local found = hashed[database]
    if found then
        return found
    else
        local metaname = addsuffix(database,"lua")
        local dataname = addsuffix(database,"dat")
        local metadata = loadtable(metaname)
        if type(metadata) ~= "table" then
            report_hashed("invalid database %a",metaname)
        elseif metadata.version ~= version then
            report_hashed("version mismatch in database %a",metaname)
        elseif not lfs.isfile(dataname) then
            report_hashed("missing data data file for %a",metaname)
        else
            return {
                database = database,
                metadata = metadata,
                dataname = dataname,
            }
        end
    end
end

local function registerhashed(database)
    if not hashed[database] then
        local valid = validhashed(database)
        if valid then
            ordered[#ordered + 1] = valid
            hashed[database] = ordered[#ordered]
            showstatus(database,valid.metadata)
        end
    end
end

local registerfilescheme  do

    local findfile = finders.file

    local list = { }
    local done = { }
    local hash = { }

    registerfilescheme = function(name)
        if not done[name] then
            list[#list+1] = name
            done[name]    = true
        end
    end

    -- why does the finder not remember ?

    function finders.file(specification,filetype)
        if type(specification) == "table" then
            local original = specification.original
         -- print(original)
            if original then
                local found = hash[original]
                if found == nil then
                    for i=1,#list do
                        local scheme = list[i]
                        local found  = finders[scheme](specification,filetype)
                        if found then
                            hash[original] = found
                            if trace_hashed then
                                report_hashed("found by auto scheme %s: %s",scheme,found)
                            end
                            return found
                        end
                    end
                    local found = findfile(specification,filetype)
                    if found then
                        hash[original] = found
                        if trace_hashed then
                            report_hashed("found by normal file scheme: %s",found)
                        end
                        return found
                    end
                    hash[original] = false
                elseif found then
                    return found
                end
                return false
            else
                -- something is wrong here, maybe we should trace it (scheme can be "unknown")
            end
        end
        -- again, something is wrong
        return findfile(specification,filetype)
    end

end

finders.helpers.validhashed        = validhashed
finders.helpers.registerhashed     = registerhashed
finders.helpers.registerfilescheme = registerfilescheme

local function locate(found,path,name)
    local files  = found.metadata.files
    local hashes = found.metadata.hashes
    local fp = files[path]
    local hash = fp and fp[name]
    if hash and hashes[hash] then
        return hash
    end
end

local function locatehash(filename,database)
    if filename then
        local name = basename(filename)
        local path = pathpart(filename)
        local hash = false
        if database then
            local found = hashed[database]
            if found then
                hash = locate(found,path,name), database, path, name
            end
        else
            for i=1,#ordered do
                local found = ordered[i]
                hash = locate(found,path,name)
                if hash then
                    database = found.database
                    break
                end
            end
        end
        if hash then
            return {
                hash = hash,
                name = name,
                path = path,
                base = database,
            }
        end
    end
end

-- no caching yet, we don't always want the file and it's fast enough

local function locateblob(filename,database)
    local found = locatehash(filename,database)
    if found then
        local database = found.base
        local data     = hashed[database]
        if data then
            local metadata = data.metadata
            local dataname = data.dataname
            local hashes   = metadata.hashes
            local blobdata = hashes[found.hash]
            if blobdata and dataname then
                local position = blobdata.position
                local f = open(dataname,"rb")
                if f then
                    f:seek("set",position)
                    local blob = f:read(blobdata.datasize)
                    if blobdata.compress == "zip" then
                        blob = zlib.decompresssize(blob,blobdata.filesize)
                    end
                    return blob
                end
            end
        end
    end
end

local finders  = resolvers.finders
local notfound = finders.notfound

function finders.hashed(specification)
    local original = specification.original
    local fullpath = specification.path
    if fullpath then
        local found = locatehash(fullpath)
        if found then
            if trace_hashed then
                report_hashed("finder: file %a found",original)
            end
            return original
        end
    end
    if trace_hashed then
        report_hashed("finder: unknown file %a",original)
    end
    return notfound()
end

local notfound   = openers.notfound
local textopener = openers.helpers.textopener

function openers.hashed(specification)
    local original = specification.original
    local fullpath = specification.path
    if fullpath then
        local found = locateblob(fullpath)
        if found then
            if trace_hashed then
                report_hashed("finder: file %a found",original)
            end
            return textopener("hashed",original,found,"utf-8")
        end
    end
    if trace_hashed then
        report_hashed("finder: unknown file %a",original)
    end
    return notfound()
end

local notfound = loaders.notfound

function loaders.hashed(specification)
    local original = specification.original
    local fullpath = specification.path
    if fullpath then
        local found = locateblob(fullpath)
        if found then
            if trace_hashed then
                report_hashed("finder: file %a found",original)
            end
            return true, found, found and #found or 0
        end
    end
    if trace_hashed then
        report_hashed("finder: unknown file %a",original)
    end
    return notfound()
end

-- this actually could end up in the generate namespace but it is not
-- really a 'generic' feature, more a module (at least for now)

local calculatehash = sha2.HEX256 -- md5.HEX is not unique enough

function resolvers.finders.helpers.createhashed(specification)
    local database = specification.database
    local patterns = specification.patterns
    if not patterns then
        local pattern = specification.pattern
        if pattern then
            patterns = {
                {
                    pattern  = pattern,
                    compress = specification.compress,
                }
            }
        end
    end
    local datname  = addsuffix(database,"dat")
    local luaname  = addsuffix(database,"lua")
    local metadata = loadtable(luaname)
    if type(metadata) ~= "table" then
        metadata = false
    elseif metadata.kind == "hashed" and metadata.version ~= version then
        report_hashed("version mismatch, starting with new table")
        metadata = false
    end
    if not metadata then
        metadata = {
            version       = version,
            kind          = "hashed",
            files         = { },
            hashes        = { },
            nofnames      = 0,
            nofpaths      = 0,
            nofblobs      = 0,
            nofcompressed = 0,
        }
    end
    local files         = metadata.files
    local hashes        = metadata.hashes
    local nofpaths      = metadata.nofpaths
    local nofnames      = metadata.nofnames
    local nofblobs      = metadata.nofblobs
    local nofcompressed = metadata.nofcompressed
    if type(patterns) == "table" then
        for i=1,#patterns do
            local pattern = patterns[i].pattern
            if pattern then
                local compress = patterns[i].compress
                local list     = dir.glob(pattern)
                local total    = #list
                report_hashed("database %a, adding pattern %a, compression %l",database,pattern,compress)
                for i=1,total do
                    local filename = list[i]
                    local name     = basename(filename)
                    local path     = pathpart(filename)
                    local data     = loaddata(filename)
                    -- cleanup
                    path = gsub(path,"^[./]*","")
                    --
                    if data then
                        local fp = files[path]
                        if not fp then
                            fp = { }
                            files[path] = fp
                            nofpaths = nofpaths + 1
                        end
                        local ff = fp[name]
                        if not ff then
                            local hash = calculatehash(data)
                            if not hashes[hash] then
                                local size = #data
                                if compress then
                                    data = zlib.compresssize(data,size)
                                    nofcompressed = nofcompressed + 1
                                end
                                local position = filesize(datname)
                                savedata(datname,data,"",true)
                                hashes[hash] = {
                                    filesize = size,
                                    datasize = #data,
                                    compress = compress and "zip",
                                    position = position,
                                }
                                nofblobs = nofblobs + 1
                            end
                            fp[name] = hash
                            nofnames = nofnames + 1
                        end
                    end
                end
            end
        end
    end
    metadata.nofpaths      = nofpaths
    metadata.nofnames      = nofnames
    metadata.nofblobs      = nofblobs
    metadata.nofcompressed = nofcompressed
    savetable(luaname, metadata)
    showstatus(database,metadata)
    return metadata
end