-- lib-core.api-discovery — Pure-Lua surface-discovery + README-parsing.
-- See: meta/docs/superpowers/specs/2026-05-16-api-doc-convention-design.md
local M = {}

-- Extracts public/private surface from Lua source code.
-- Convention: `M.<name> = function(...)` is public; `M._<name> = ...` is private.
-- Returns: { public = ["foo","bar",...], private = ["_baz",...] }
function M.parse_lua_surface(source_string)
    local public  = {}
    local private = {}
    for name in string.gmatch(source_string, "M%.([_%w]+)%s*=%s*function") do
        if string.sub(name, 1, 1) == "_" then
            table.insert(private, name)
        else
            table.insert(public, name)
        end
    end
    return { public = public, private = private }
end

-- Extracts documented function-names from README's "## API" section.
-- Parses H3-Headers like "### `input.bind(action_name, keys)`" → "bind".
-- Convention: H3 header opens with backtick, function-name follows after optional namespace-dot.
-- Returns: { documented = ["bind","unbind",...] }
function M.parse_readme_api(markdown_string)
    local documented = {}
    -- Find "## API" section start (allow trailing whitespace/content)
    local api_start = string.find(markdown_string, "\n## API[%s\n]")
    if not api_start then
        return { documented = documented }
    end
    -- Find next H2 (terminate API section)
    local api_end = string.find(markdown_string, "\n## ", api_start + 5)
    local section = string.sub(markdown_string, api_start, api_end or #markdown_string)

    -- Match H3 headers: "### `[namespace.]name(...)`" — capture name portion
    for line in string.gmatch(section, "###%s+`[^.`]*%.?([_%w]+)%s*[%(`]") do
        table.insert(documented, line)
    end
    return { documented = documented }
end

-- Diffs code-surface vs README-doc.
-- Compares surface.public (set) vs readme.documented (set).
-- Returns: { missing_docs = [...], stale_docs = [...] }
function M.diff_surface(surface, readme)
    local public_set = {}
    for _, name in ipairs(surface.public) do public_set[name] = true end
    local doc_set = {}
    for _, name in ipairs(readme.documented) do doc_set[name] = true end

    local missing = {}
    for name in pairs(public_set) do
        if not doc_set[name] then table.insert(missing, name) end
    end
    local stale = {}
    for name in pairs(doc_set) do
        if not public_set[name] then table.insert(stale, name) end
    end
    table.sort(missing); table.sort(stale)
    return { missing_docs = missing, stale_docs = stale }
end

-- Extracts unique engine.<namespace>.<func> calls from Lua source.
-- Returns: array of unique strings, sorted.
function M.grep_engine_calls(source_string)
    local seen = {}
    for call in string.gmatch(source_string, "(engine%.[_%w]+%.[_%w]+)") do
        seen[call] = true
    end
    local out = {}
    for call in pairs(seen) do table.insert(out, call) end
    table.sort(out)
    return out
end

return M