-- create a temporary table called tmp_TBLNAME, mimicking existing table
-- TBLNAME
--
-- Args:
--     tblname: name of the table to mimick
create or replace function swh_mktemp(tblname regclass)
    returns void
    language plpgsql
as $$
begin
    execute format('
	create temporary table tmp_%I
	    (like %I including defaults)
	    on commit drop
	', tblname, tblname);
    return;
end
$$;


-- create a temporary table for directory entries called tmp_TBLNAME,
-- mimicking existing table TBLNAME with an extra dir_id (sha1_git)
-- column, and dropping the id column.
--
-- This is used to create the tmp_directory_entry_<foo> tables.
--
-- Args:
--     tblname: name of the table to mimick
create or replace function swh_mktemp_dir_entry(tblname regclass)
    returns void
    language plpgsql
as $$
begin
    execute format('
	create temporary table tmp_%I
	    (like %I including defaults, dir_id sha1_git)
	    on commit drop;
        alter table tmp_%I drop column id;
	', tblname, tblname, tblname, tblname);
    return;
end
$$;


-- create a temporary table for revisions called tmp_revisions,
-- mimicking existing table revision, replacing the foreign keys to
-- people with an email and name field
--
create or replace function swh_mktemp_revision()
    returns void
    language sql
as $$
    create temporary table tmp_revision (
        like revision including defaults,
        author_name text not null default '',
        author_email text not null default '',
        committer_name text not null default '',
        committer_email text not null default ''
    ) on commit drop;
    alter table tmp_revision drop column author;
    alter table tmp_revision drop column committer;
$$;


-- create a temporary table for releases called tmp_release,
-- mimicking existing table release, replacing the foreign keys to
-- people with an email and name field
--
create or replace function swh_mktemp_release()
    returns void
    language sql
as $$
    create temporary table tmp_release (
        like release including defaults,
        author_name text not null default '',
        author_email text not null default ''
    ) on commit drop;
    alter table tmp_release drop column author;
$$;


-- a content signature is a set of cryptographic checksums that we use to
-- uniquely identify content, for the purpose of verifying if we already have
-- some content or not during content injection
create type content_signature as (
    sha1      sha1,
    sha1_git  sha1_git,
    sha256    sha256
);


-- check which entries of tmp_content are missing from content
--
-- operates in bulk: 0. swh_mktemp(content), 1. COPY to tmp_content,
-- 2. call this function
create or replace function swh_content_missing()
    returns setof content_signature
    language plpgsql
as $$
begin
    -- This query is critical for (single-algorithm) hash collision detection,
    -- so we cannot rely only on the fact that a single hash (e.g., sha1) is
    -- missing from the table content to conclude that a given content is
    -- missing. Ideally, we would want to (try to) add to content all entries
    -- in tmp_content that, when considering all columns together, are missing
    -- from content.
    --
    -- But doing that naively would require a *compound* index on all checksum
    -- columns; that index would not be significantly smaller than the content
    -- table itself, and therefore won't be used. Therefore we union together
    -- all contents that differ on at least one column from what is already
    -- available. If there is a collision on some (but not all) columns, the
    -- relevant tmp_content entry will be included in the set of content to be
    -- added, causing a downstream violation of unicity constraint.
    return query
	(select sha1, sha1_git, sha256 from tmp_content as tmp
	 where not exists
	     (select 1 from content as c where c.sha1 = tmp.sha1))
	union
	(select sha1, sha1_git, sha256 from tmp_content as tmp
	 where not exists
	     (select 1 from content as c where c.sha1_git = tmp.sha1_git))
	union
	(select sha1, sha1_git, sha256 from tmp_content as tmp
	 where not exists
	     (select 1 from content as c where c.sha256 = tmp.sha256));
    return;
end
$$;


-- check which entries of tmp_skipped_content are missing from skipped_content
--
-- operates in bulk: 0. swh_mktemp(skipped_content), 1. COPY to tmp_skipped_content,
-- 2. call this function
create or replace function swh_skipped_content_missing()
    returns setof content_signature
    language plpgsql
as $$
begin
    return query
	select sha1, sha1_git, sha256 from tmp_skipped_content
	where not exists
	(select 1 from skipped_content s where
	    sha1 is not distinct from s.sha1 and
	    sha1_git is not distinct from s.sha1_git and
	    sha256 is not distinct from s.sha256);
    return;
end
$$;


-- Look up content based on one or several different checksums. Return all
-- content information if the content is found; a NULL row otherwise.
--
-- At least one checksum should be not NULL. If several are not NULL, they will
-- be AND-ed together in the lookup query.
--
-- Note: this function is meant to be used to look up individual contents
-- (e.g., for the web app), for batch lookup of missing content (e.g., to be
-- added) see swh_content_missing
create or replace function swh_content_find(
    sha1      sha1     default NULL,
    sha1_git  sha1_git default NULL,
    sha256    sha256   default NULL
)
    returns content
    language plpgsql
as $$
declare
    con content;
    filters text[] := array[] :: text[];  -- AND-clauses used to filter content
    q text;
begin
    if sha1 is not null then
        filters := filters || format('sha1 = %L', sha1);
    end if;
    if sha1_git is not null then
        filters := filters || format('sha1_git = %L', sha1_git);
    end if;
    if sha256 is not null then
        filters := filters || format('sha256 = %L', sha256);
    end if;

    if cardinality(filters) = 0 then
        return null;
    else
        q = format('select * from content where %s',
	        array_to_string(filters, ' and '));
        execute q into con;
	return con;
    end if;
end
$$;


-- add tmp_content entries to content, skipping duplicates
--
-- operates in bulk: 0. swh_mktemp(content), 1. COPY to tmp_content,
-- 2. call this function
create or replace function swh_content_add()
    returns void
    language plpgsql
as $$
begin
    insert into content (sha1, sha1_git, sha256, length, status)
	select distinct sha1, sha1_git, sha256, length, status
	from tmp_content
	where (sha1, sha1_git, sha256) in
	    (select * from swh_content_missing());
	    -- TODO XXX use postgres 9.5 "UPSERT" support here, when available.
	    -- Specifically, using "INSERT .. ON CONFLICT IGNORE" we can avoid
	    -- the extra swh_content_missing() query here.
    return;
end
$$;


-- add tmp_skipped_content entries to skipped_content, skipping duplicates
--
-- operates in bulk: 0. swh_mktemp(skipped_content), 1. COPY to tmp_skipped_content,
-- 2. call this function
create or replace function swh_skipped_content_add()
    returns void
    language plpgsql
as $$
begin
    insert into skipped_content (sha1, sha1_git, sha256, length, status, reason, origin)
	select distinct sha1, sha1_git, sha256, length, status, reason, origin
	from tmp_skipped_content
	where (coalesce(sha1, ''), coalesce(sha1_git, ''), coalesce(sha256, '')) in
	    (select coalesce(sha1, ''), coalesce(sha1_git, ''), coalesce(sha256, '') from swh_skipped_content_missing());
	    -- TODO XXX use postgres 9.5 "UPSERT" support here, when available.
	    -- Specifically, using "INSERT .. ON CONFLICT IGNORE" we can avoid
	    -- the extra swh_content_missing() query here.
    return;
end
$$;


-- check which entries of tmp_directory are missing from directory
--
-- operates in bulk: 0. swh_mktemp(directory), 1. COPY to tmp_directory,
-- 2. call this function
create or replace function swh_directory_missing()
    returns setof sha1_git
    language plpgsql
as $$
begin
    return query
	select id from tmp_directory
	except
	select id from directory;
    return;
end
$$;


create type directory_entry_type as enum('file', 'dir', 'rev');


-- Add tmp_directory_entry_* entries to directory_entry_* and directory,
-- skipping duplicates in directory_entry_*.  This is a generic function that
-- works on all kind of directory entries.
--
-- operates in bulk: 0. swh_mktemp_dir_entry('directory_entry_*'), 1 COPY to
-- tmp_directory_entry_*, 2. call this function
--
-- Assumption: this function is used in the same transaction that inserts the
-- context directory in table "directory".
create or replace function swh_directory_entry_add(typ directory_entry_type)
    returns void
    language plpgsql
as $$
begin
    execute format('
    insert into directory_entry_%1$s (target, name, perms, atime, mtime, ctime)
    select distinct t.target, t.name, t.perms, t.atime, t.mtime, t.ctime
    from tmp_directory_entry_%1$s t
    where not exists (
    select 1
    from directory_entry_%1$s i
    where t.target = i.target and t.name = i.name and t.perms = i.perms and
       t.atime is not distinct from i.atime and
       t.mtime is not distinct from i.mtime and
       t.ctime is not distinct from i.ctime)
   ', typ);

    execute format('
    with new_entries as (
	select t.dir_id, array_agg(i.id) as entries
	from tmp_directory_entry_%1$s t
	inner join directory_entry_%1$s i
	on t.target = i.target and t.name = i.name and t.perms = i.perms and
	   t.atime is not distinct from i.atime and
	   t.mtime is not distinct from i.mtime and
	   t.ctime is not distinct from i.ctime
	group by t.dir_id
    )
    update directory as d
    set %1$s_entries = new_entries.entries
    from new_entries
    where d.id = new_entries.dir_id
    ', typ);

    return;
end
$$;


-- a directory listing entry with all the metadata
--
-- can be used to list a directory, and retrieve all the data in one go.
create type directory_entry as
(
  dir_id  sha1_git,     -- id of the parent directory
  type    directory_entry_type,  -- type of entry
  target  sha1_git,     -- id of target
  name    unix_path,    -- path name, relative to containing dir
  perms   file_perms,   -- unix-like permissions
  atime   timestamptz,  -- time of last access
  mtime   timestamptz,  -- time of last modification
  ctime   timestamptz   -- time of last status change
);


-- List a single level of directory walked_dir_id
create or replace function swh_directory_walk_one(walked_dir_id sha1_git)
    returns setof directory_entry
    language sql
as $$
    with dir as (
	select id as dir_id, dir_entries, file_entries, rev_entries
	from directory
	where id = walked_dir_id),
    ls_d as (select dir_id, unnest(dir_entries) as entry_id from dir),
    ls_f as (select dir_id, unnest(file_entries) as entry_id from dir),
    ls_r as (select dir_id, unnest(rev_entries) as entry_id from dir)
    (select dir_id, 'dir'::directory_entry_type as type,
	    target, name, perms, atime, mtime, ctime
     from ls_d
     left join directory_entry_dir d on ls_d.entry_id = d.id)
    union
    (select dir_id, 'file'::directory_entry_type as type,
	    target, name, perms, atime, mtime, ctime
     from ls_f
     left join directory_entry_file d on ls_f.entry_id = d.id)
    union
    (select dir_id, 'rev'::directory_entry_type as type,
	    target, name, perms, atime, mtime, ctime
     from ls_r
     left join directory_entry_rev d on ls_r.entry_id = d.id)
    order by name;
$$;


-- List all revision IDs starting from a given revision, going back in time
--
-- TODO ordering: should be breadth-first right now (what do we want?)
-- TODO ordering: ORDER BY parent_rank somewhere?
create or replace function swh_revision_list(root_revision sha1_git)
    returns setof sha1_git
    language sql
as $$
    with recursive rev_list(id) as (
	(select id from revision where id = root_revision)
	union
	(select parent_id
	 from revision_history as h
	 join rev_list on h.id = rev_list.id)
    )
    select * from rev_list;
$$;


-- Detailed entry in a revision log
create type revision_log_entry as
(
  id                     sha1_git,
  date                   timestamptz,
  date_offset            smallint,
  committer_date         timestamptz,
  committer_date_offset  smallint,
  type                   revision_type,
  directory              sha1_git,
  message                bytea,
  author_name            text,
  author_email           text,
  committer_name         text,
  committer_email        text
);


-- "git style" revision log. Similar to swh_revision_list(), but returning all
-- information associated to each revision, and expanding authors/committers
create or replace function swh_revision_log(root_revision sha1_git)
    returns setof revision_log_entry
    language sql
as $$
    select revision.id, date, date_offset,
	committer_date, committer_date_offset,
	type, directory, message,
	author.name as author_name, author.email as author_email,
	committer.name as committer_name, committer.email as committer_email
    from swh_revision_list(root_revision) as rev_list
    join revision on revision.id = rev_list
    join person as author on revision.author = author.id
    join person as committer on revision.committer = committer.id;
$$;


-- List missing revisions from tmp_revision
create or replace function swh_revision_missing()
    returns setof sha1_git
    language plpgsql
as $$
begin
    return query
        select id from tmp_revision
	except
	select id from revision;
    return;
end
$$;


-- Create entries in person from tmp_revision
create or replace function swh_person_add_from_revision()
    returns void
    language plpgsql
as $$
begin
    with t as (
        select author_name as name, author_email as email from tmp_revision
    union
        select committer_name as name, committer_email as email from tmp_revision
    ) insert into person (name, email)
    select distinct name, email from t
    where not exists (
        select 1
	from person p
	where t.name = p.name and t.email = p.email
    );
    return;
end
$$;


-- Create entries in revision from tmp_revision
create or replace function swh_revision_add()
    returns void
    language plpgsql
as $$
begin
    perform swh_person_add_from_revision();

    insert into revision (id, date, date_offset, committer_date, committer_date_offset, type, directory, message, author, committer)
    select t.id, t.date, t.date_offset, t.committer_date, t.committer_date_offset, t.type, t.directory, t.message, a.id, c.id
    from tmp_revision t
    left join person a on a.name = t.author_name and a.email = t.author_email
    left join person c on c.name = t.committer_name and c.email = t.committer_email;
    return;
end
$$;


-- List missing releases from tmp_release
create or replace function swh_release_missing()
    returns setof sha1_git
    language plpgsql
as $$
begin
    return query
        select id from tmp_release
	except
	select id from release;
    return;
end
$$;


-- Create entries in person from tmp_release
create or replace function swh_person_add_from_release()
    returns void
    language plpgsql
as $$
begin
    with t as (
        select distinct author_name as name, author_email as email from tmp_release
    ) insert into person (name, email)
    select name, email from t
    where not exists (
        select 1
	from person p
	where t.name = p.name and t.email = p.email
    );
    return;
end
$$;


-- Create entries in release from tmp_release
create or replace function swh_release_add()
    returns void
    language plpgsql
as $$
begin
    perform swh_person_add_from_release();

    insert into release (id, revision, date, date_offset, name, comment, author)
    select t.id, t.revision, t.date, t.date_offset, t.name, t.comment, a.id
    from tmp_release t
    left join person a on a.name = t.author_name and a.email = t.author_email;
    return;
end
$$;


-- Absolute path: directory reference + complete path relative to it
create type content_dir as (
    directory  sha1_git,
    path       unix_path
);


-- Find the containing directory of a given content, specified by sha1
-- (note: *not* sha1_git).
--
-- Return a pair (dir_it, path) where path is a UNIX path that, from the
-- directory root, reach down to a file with the desired content. Return NULL
-- if no match is found.
--
-- In case of multiple paths (i.e., pretty much always), an arbitrary one is
-- chosen.
create or replace function swh_content_find_directory(content_id sha1)
    returns content_dir
    language sql
as $$
    with recursive path as (
	-- Recursively build a path from the requested content to a root
	-- directory. Each iteration returns a pair (dir_id, filename) where
	-- filename is relative to dir_id. Stops when no parent directory can
	-- be found.
	(select dir.id as dir_id, dir_entry_f.name as name, 0 as depth
	 from directory_entry_file as dir_entry_f
	 join content on content.sha1_git = dir_entry_f.target
	 join directory as dir on dir.file_entries @> array[dir_entry_f.id]
	 where content.sha1 = content_id
	 limit 1)
	union all
	(select dir.id as dir_id,
		(dir_entry_d.name || '/' || path.name)::unix_path as name,
		path.depth + 1
	 from path
	 join directory_entry_dir as dir_entry_d on dir_entry_d.target = path.dir_id
	 join directory as dir on dir.dir_entries @> array[dir_entry_d.id]
	 limit 1)
    )
    select dir_id, name from path order by depth desc limit 1;
$$;


-- Walk the revision history starting from a given revision, until a matching
-- occurrence is found. Return all occurrence information if one is found, NULL
-- otherwise.
create or replace function swh_revision_find_occurrence(revision_id sha1_git)
    returns occurrence
    language plpgsql
as $$
declare
    occ occurrence%ROWTYPE;
    rev sha1_git;
begin
    -- first check to see if revision_id is already pointed by an occurrence
    select origin, branch, revision
    from occurrence_history as occ_hist
    where occ_hist.revision = revision_id
    order by upper(occ_hist.validity)  -- TODO filter by authority?
    limit 1
    into occ;

    -- no occurrence point to revision_id, walk up the history
    if not found then
        -- recursively walk the history, stopping immediately before a revision
        -- pointed to by an occurrence.
	-- TODO find a nicer way to stop at, but *including*, that revision
	with recursive revlog as (
	    (select revision_id as rev_id, 0 as depth)
	    union all
	    (select hist.parent_id as rev_id, revlog.depth + 1
	     from revlog
	     join revision_history as hist on hist.id = revlog.rev_id
	     and not exists(select 1 from occurrence_history
			    where revision = hist.parent_id)
	     limit 1)
	)
	select rev_id from revlog order by depth desc limit 1
	into rev;
	if not found then return null; end if;

	-- as we stopped before a pointed by revision, look it up again and
	-- return its data
	select origin, branch, revision
	from revision_history as rev_hist, occurrence_history as occ_hist
	where rev_hist.id = rev
	and occ_hist.revision = rev_hist.parent_id
	order by upper(occ_hist.validity)  -- TODO filter by authority?
	limit 1
	into occ;
    end if;

    return occ;  -- might be NULL
end
$$;


-- Occurrence of some content in a given context
create type content_occurrence as (
    origin_type	 text,
    origin_url	 text,
    branch	 text,
    revision_id	 sha1_git,
    path	 unix_path
);


-- Given the sha1 of some content, look up an occurrence that points to a
-- revision, which in turns reference (transitively) a tree containing the
-- content. Answer the question: "where/when did SWH see a given content"?
-- Return information about an arbitrary occurrence/revision/tree if one is
-- found, NULL otherwise.
create or replace function swh_content_find_occurrence(content_id sha1)
    returns content_occurrence
    language plpgsql
as $$
declare
    dir content_dir;
    rev sha1_git;
    occ occurrence%ROWTYPE;
    coc content_occurrence;
begin
    -- each step could fail if no results are found, and that's OK
    select * from swh_content_find_directory(content_id)     -- look up directory
	into dir;
    if not found then return null; end if;

    select id from revision where directory = dir.directory  -- look up revision
	limit 1
	into rev;
    if not found then return null; end if;

    select * from swh_revision_find_occurrence(rev)	     -- look up occurrence
	into occ;
    if not found then return null; end if;

    select origin.type, origin.url, occ.branch, rev, dir.path
    from origin
    where origin.id = occ.origin
    into coc;

    return coc;  -- might be NULL
end
$$;