-- 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> public; M._<name> private.
-- Supports both explicit assignment (`M.foo = function`) and syntax sugar
-- (`function M.foo`) — Lua treats them semantically identical.
-- Returns: { public = ["foo","bar",...], private = ["_baz",...] }
function M.parse_lua_surface(source_string)
    -- Strip Lua line-comments (-- to end-of-line) before pattern matching.
    -- This prevents false-positive matches inside commented-out forward-compat
    -- stubs (e.g. DEPRECATED-MVP placeholders).
    -- Block comments (--[[...]]) are not handled; not used in Sporel-lib code.
    -- Caveat: a literal "--" inside a string would also be stripped; acceptable
    -- for the lint-tool's purpose (false-negatives in pathological string cases
    -- are preferable to false-positives on commented stubs).
    local stripped = string.gsub(source_string, "%-%-[^\n]*", "")

    local public  = {}
    local private = {}
    local seen    = {}

    local function classify(name)
        if seen[name] then return end
        seen[name] = true
        if string.sub(name, 1, 1) == "_" then
            table.insert(private, name)
        else
            table.insert(public, name)
        end
    end

    -- Form 1: M.foo = function(...)
    for name in string.gmatch(stripped, "M%.([_%w]+)%s*=%s*function") do
        classify(name)
    end

    -- Form 2: function M.foo(...)
    for name in string.gmatch(stripped, "function%s+M%.([_%w]+)") do
        classify(name)
    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 = {}
    local seen = {}

    -- 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)

    -- Two-pass matching to handle both namespace-prefixed and namespace-less
    -- function-names in H3 headers.
    -- Pattern 1: namespaced — "### `ns.func(...)`" -> capture "func"
    for name in string.gmatch(section, "###%s+`[%w_]+%.([_%w]+)") do
        if not seen[name] then
            seen[name] = true
            table.insert(documented, name)
        end
    end
    -- Pattern 2: namespace-less — "### `func(...)`" -> capture "func"
    -- The seen-set prevents re-matching names already captured by pattern 1.
    for name in string.gmatch(section, "###%s+`([_%w]+)%s*[%(`]") do
        if not seen[name] then
            seen[name] = true
            table.insert(documented, name)
        end
    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

-- Generates mermaid topology-block from manifest + engine_calls.
-- engine_calls: array from grep_engine_calls (presence determines engine-node).
-- Returns: mermaid-source-string (no markers - caller wraps).
function M.generate_topology_block(manifest, engine_calls)
    local lines = {"graph LR"}
    local self_node = string.format('  this["%s"]', manifest.id)
    table.insert(lines, self_node)

    if manifest.deps then
        for _, dep in ipairs(manifest.deps) do
            local dep_var = string.gsub(dep.id, "[%-%.]", "_")
            table.insert(lines, string.format('  %s["%s"]', dep_var, dep.id))
            table.insert(lines, string.format('  this --> %s', dep_var))
        end
    end

    if engine_calls and #engine_calls > 0 then
        table.insert(lines, '  engine["engine.*"]')
        table.insert(lines, '  this --> engine')
    end

    return table.concat(lines, "\n")
end

-- Validates README structure against MUST-sections for the given tier.
-- Tier "core" enforces: H1, Abstract, Badges, Topology, Topology-Block, API, References.
-- Tier "engine" enforces the same MUST-sections, but the Badges check accepts
--   any bold key:value line (engine README has no Lib-ID; instead Version/License).
-- Tier "community" enforces nothing (returns empty result).
-- Returns: { missing_sections = [...], section_order_ok = bool }
function M.validate_readme_structure(markdown_string, tier)
    if tier == "community" then
        return { missing_sections = {}, section_order_ok = true }
    end

    -- Both "core" and "engine" tiers use the same MUST-sections list.
    -- Difference is handled upstream (engine tier skips parse_lua_surface etc.).
    local missing = {}
    local checks = {
        { name = "H1",             pattern = "^#%s+%S" },
        { name = "Badges",         pattern = "\n%*%*Lib%-ID:%*%*%s*lib%-" },
        { name = "Topology",       pattern = "\n##%s+Topology[%s\n]" },
        { name = "Topology-Block", pattern = "<!%-%-%s*topology:start" },
        { name = "API",            pattern = "\n##%s+API[%s\n]" },
        { name = "References",     pattern = "\n##%s+References[%s\n]" },
    }

    -- Engine-tier: relax the Badges check (engine uses "Version", "License" etc.
    -- instead of a "Lib-ID:" prefix — engine is not a lib).
    if tier == "engine" then
        checks[2] = { name = "Badges", pattern = "\n%*%*[%w%-]+:%*%*" }
    end

    for _, c in ipairs(checks) do
        if not string.find(markdown_string, c.pattern) then
            table.insert(missing, c.name)
        end
    end

    -- Order check: API must appear before References in source order
    local api_pos = string.find(markdown_string, "\n##%s+API[%s\n]")
    local ref_pos = string.find(markdown_string, "\n##%s+References[%s\n]")
    local order_ok = (api_pos and ref_pos and api_pos < ref_pos) or (not api_pos and not ref_pos)

    return { missing_sections = missing, section_order_ok = order_ok }
end

return M