-- SPDX-FileCopyrightText: © 2026 Vladimir Zorin <vladimir@deviant.guru>
-- SPDX-License-Identifier: LicenseRef-OWL-1.0-or-later
-- Licensed under OWL v1.0+. See LICENSE.

--- Default web_search backend backed by the Linkup /search endpoint.
-- See https://docs.linkup.so/pages/documentation/endpoints/search/reference
-- The API key is read from the LINKUP_API_KEY env var by default.

local http = require("http")
local json = require("cjson.safe")

local M = {}

local DEFAULT_ENDPOINT = "https://api.linkup.so/v1/search"
local DEFAULT_DEPTH = "standard"
local DEFAULT_OUTPUT_TYPE = "sourcedAnswer"
local DEFAULT_API_KEY_ENV = "LINKUP_API_KEY"

local function non_empty_string(value)
	return type(value) == "string" and value ~= ""
end

local function non_empty_array(value)
	return type(value) == "table" and #value > 0
end

-- Map Linkup sources ({name, url, favicon, snippet}) onto web_search's
-- expected source shape.
local function normalize_sources(sources)
	local out = {}
	if type(sources) ~= "table" then
		return out
	end
	for _, src in ipairs(sources) do
		if type(src) == "table" then
			out[#out + 1] = {
				title = src.name,
				url = src.url,
				snippet = src.snippet,
			}
		end
	end
	return out
end

--- Construct a search backend function.
-- @param opts table  optional overrides: api_key, api_key_env, endpoint,
--   depth, output_type, max_results, timeout
-- @return function search(query, search_opts) -> (result, err)
function M.new(opts)
	opts = opts or {}

	local api_key_env = non_empty_string(opts.api_key_env) and opts.api_key_env or DEFAULT_API_KEY_ENV
	local endpoint = non_empty_string(opts.endpoint) and opts.endpoint or DEFAULT_ENDPOINT
	local depth = non_empty_string(opts.depth) and opts.depth or DEFAULT_DEPTH
	local output_type = non_empty_string(opts.output_type) and opts.output_type or DEFAULT_OUTPUT_TYPE

	return function(query, search_opts)
		search_opts = search_opts or {}

		local api_key = opts.api_key
		if not non_empty_string(api_key) then
			api_key = os.getenv(api_key_env)
		end
		if not non_empty_string(api_key) then
			return nil, api_key_env .. " is not set"
		end

		local body = {
			q = query,
			depth = depth,
			outputType = output_type,
		}
		if non_empty_array(search_opts.include_domains) then
			body.includeDomains = search_opts.include_domains
		end
		if non_empty_array(search_opts.exclude_domains) then
			body.excludeDomains = search_opts.exclude_domains
		end
		if type(opts.max_results) == "number" then
			body.maxResults = opts.max_results
		end

		local ok_encode, encoded = pcall(json.encode, body)
		if not ok_encode or type(encoded) ~= "string" then
			return nil, "failed to encode search request"
		end

		local resp, req_err = http.request(endpoint, {
			method = "POST",
			body = encoded,
			headers = {
				authorization = "Bearer " .. api_key,
				["content-type"] = "application/json",
				accept = "application/json",
			},
		}, opts.timeout)

		if not resp then
			return nil, "search request failed: " .. tostring(req_err or "unknown error")
		end
		if type(resp.status) ~= "number" then
			return nil, "search response missing status"
		end
		if resp.status < 200 or resp.status >= 300 then
			local detail = non_empty_string(resp.body) and resp.body or ""
			return nil, "search request failed with status " .. tostring(resp.status) .. " " .. detail
		end

		local payload = json.decode(resp.body or "")
		if type(payload) ~= "table" then
			return nil, "failed to decode search response"
		end

		return {
			answer = payload.answer,
			sources = normalize_sources(payload.sources),
			metadata = {
				depth = depth,
				output_type = output_type,
				status = resp.status,
			},
		}
	end
end

return M