package responses

import (
	"net/url"
	"strings"

	"reasonix/internal/provider"
)

// vendorCapabilities describes how a Responses-compatible endpoint deviates
// from the base OpenAI Responses wire behavior. Vendors are detected from the
// base URL (DetectVendor); unknown endpoints get the zero value, which is the
// standard OpenAI-compatible behavior (stateful, no session-cache header, no
// summary requirement, no tool-call reasoning retention, temperature honored).
//
// This table is the single source of truth for wire-level vendor differences:
// adding a new Responses-compatible vendor means adding one entry here and a
// base-URL case in DetectVendor — not threading more string comparisons
// through responses.go.
type vendorCapabilities struct {
	// stateless marks endpoints that reject previous_response_id and require
	// the full input history on every turn (DeepSeek, MiMo). stateful is the
	// OpenAI default.
	stateless bool

	// sessionCacheHeader marks DashScope, whose session cache must be opted
	// into with the x-dashscope-session-cache header.
	sessionCacheHeader bool

	// toolCallReasoning marks stateless vendors whose documentation requires
	// retaining historical reasoning content in the input on multi-turn tool
	// calls (DeepSeek, MiMo).
	toolCallReasoning bool

	// singleSegmentReasoning marks endpoints whose thinking is one
	// uninterruptible segment per turn: the server emits reasoning and the
	// final answer atomically, and a new reasoning segment only starts on a
	// brand-new turn — never mid-turn after a tool call. MiMo documents this
	// ("reasoning.effort: low/medium/high all enable reasoning, no strength
	// differentiation"; tool-call turns carry one segment). DeepSeek, by
	// contrast, can emit several reasoning segments across a turn's tool
	// loop. Callers must not expect a multi-segment chain-of-thought from
	// single-segment vendors.
	singleSegmentReasoning bool

	// ignoresTemperature marks vendors that force temperature/top_p to their
	// defaults in thinking mode, so sending them is a no-op (MiMo forces
	// 1.0 / 0.95). Keeps the wire request lean for such endpoints.
	ignoresTemperature bool

	// defaultMaxOutputTokens is the max_output_tokens sent when the caller
	// did not request one (req.MaxTokens == 0). Zero means "leave unset and
	// let the server use its own default". MiMo's server default (32768)
	// covers reasoning + visible output, and its thinking mode can spend a
	// large chunk of that budget on reasoning before the visible answer —
	// truncating tool calls mid-JSON on long turns. Raise it to the next
	// documented tier (65536, within the allowed [1, 131072] range) so the
	// answer survives long reasoning.
	defaultMaxOutputTokens int

	// compactionOutputTokens is the separate budget for native/summary
	// compaction calls. Zero means "no dedicated compaction budget; fall
	// back to ordinary summarize without inheriting a large default".
	compactionOutputTokens int

	// summaryRequired marks vendors whose Responses API requires the
	// `summary` list on input reasoning items (DashScope; without it the
	// server rejects with "Invalid 'summary': summary is required..."). The
	// OpenAI base format only needs `content`. Sending `summary` to vendors
	// that do not define it (MiMo) leaks the reasoning text into an extra
	// field the server may fold back into the model context, doubling the
	// chain-of-thought echoed each turn and inflating reasoning output
	// until truncation. Only send it where the wire demands it.
	summaryRequired bool
}

var vendorTable = map[string]vendorCapabilities{
	"dashscope": {
		stateless:              false,
		sessionCacheHeader:     true,
		toolCallReasoning:      false,
		singleSegmentReasoning: false,
		ignoresTemperature:     false,
		summaryRequired:        true,
		// No native compact endpoint yet; summarize fallback only.
		compactionOutputTokens: 8192,
	},
	"deepseek": {
		stateless:              true,
		sessionCacheHeader:     false,
		toolCallReasoning:      true,
		singleSegmentReasoning: false,
		ignoresTemperature:     false,
		// 0 = omit max_output_tokens; official server ceiling is 384K.
		defaultMaxOutputTokens: 0,
		// Compaction summaries use a dedicated 16K-class budget, independent of
		// ordinary answer output.
		compactionOutputTokens: provider.DefaultOrdinaryOutputTokens,
	},
	"mimo": {
		stateless:              true,
		sessionCacheHeader:     false,
		toolCallReasoning:      true,
		singleSegmentReasoning: true,
		ignoresTemperature:     true,
		// Coding-agent default 32K; users may raise explicitly. Not 128K auto.
		defaultMaxOutputTokens: provider.DefaultReasoningOutputTokens,
		compactionOutputTokens: provider.DefaultOrdinaryOutputTokens,
	},
	// StepFun's Responses API accepts reasoning items only with a `summary`
	// list and silently ignores previous_response_id (verified live: a
	// continuation request billed only the new-turn tokens and the model
	// hallucinated unrelated context), so it is stateless like DeepSeek but
	// needs the summary field like DashScope. Only step-3.7-flash is enabled
	// server-side; the wire shape is identical on the standard and step_plan
	// hosts, so one entry covers both.
	"stepfun": {
		stateless:              true,
		sessionCacheHeader:     false,
		toolCallReasoning:      true,
		singleSegmentReasoning: false,
		ignoresTemperature:     false,
		summaryRequired:        true,
		compactionOutputTokens: provider.DefaultOrdinaryOutputTokens,
	},
	// "" (unknown OpenAI-compatible endpoint) → zero value = default behavior.
	// Unknown gateways deliberately do NOT inherit a large max-output default.
}

// capabilitiesFor returns the wire capabilities for a detected vendor name.
// Unknown vendors fall back to the zero value (standard OpenAI behavior).
func capabilitiesFor(vendor string) vendorCapabilities {
	return vendorTable[vendor]
}

// DetectVendor identifies endpoint behavior that affects the Responses wire.
// Empty means an unknown OpenAI-compatible endpoint with default behavior.
func DetectVendor(baseURL string) string {
	u, err := url.Parse(strings.TrimSpace(baseURL))
	if err != nil {
		return ""
	}
	host := strings.ToLower(u.Hostname())
	switch {
	case host == "dashscope.aliyuncs.com", strings.HasSuffix(host, ".dashscope.aliyuncs.com"), strings.HasSuffix(host, ".maas.aliyuncs.com"):
		return "dashscope"
	case host == "api.deepseek.com", strings.HasSuffix(host, ".deepseek.com"):
		return "deepseek"
	case host == "api.xiaomimimo.com", strings.HasSuffix(host, ".xiaomimimo.com"):
		return "mimo"
	case host == "api.stepfun.com", host == "api.stepfun.ai":
		return "stepfun"
	default:
		return ""
	}
}