package proxy

import (
	"crypto/rand"
	"encoding/hex"
	"sync"
	"time"
)

// ZenBaseURL is the upstream OpenCode Zen API base URL.
const ZenBaseURL = "https://opencode.ai/zen/v1"

// Free models available via OpenCode Zen (no API key required).
// These are the 5 models currently offered for free.
var zenModels = []ModelInfo{
	{
		ID:              "big-pickle",
		Name:            "Big Pickle (Free)",
		OwnedBy:         "opencode-zen",
		ContextWindow:   200_000,
		MaxOutputTokens: 32_000,
		Description:     "Permanentemente gratis. Código legacy, refactors, mantenimiento.",
		SupportsVision:  false,
	},
	{
		ID:              "deepseek-v4-flash-free",
		Name:            "DeepSeek V4 Flash (Free)",
		OwnedBy:         "deepseek",
		ContextWindow:   1_000_000,
		MaxOutputTokens: 384_000,
		Description:     "El todoterreno. 1M contexto, 284B params (13B activos), razonamiento.",
		SupportsVision:  false,
	},
	{
		ID:              "mimo-v2.5-free",
		Name:            "MiMo V2.5 (Free)",
		OwnedBy:         "xiaomi",
		ContextWindow:   1_000_000,
		MaxOutputTokens: 32_000,
		Description:     "Multimodal de Xiaomi. 1M contexto, imágenes → código. MIT license.",
		SupportsVision:  true,
	},
	{
		ID:              "north-mini-code-free",
		Name:            "North Mini Code (Free)",
		OwnedBy:         "cohere",
		ContextWindow:   256_000,
		MaxOutputTokens: 64_000,
		Description:     "Cohere. 30B total / 3B activos (MoE). Respuesta rápida, scripts.",
		SupportsVision:  false,
	},
	{
		ID:              "nemotron-3-ultra-free",
		Name:            "Nemotron 3 Ultra (Free)",
		OwnedBy:         "nvidia",
		ContextWindow:   1_000_000,
		MaxOutputTokens: 16_384,
		Description:     "NVIDIA. 550B params (55B activos). Mamba-2 + MoE híbrido. Razonamiento.",
		SupportsVision:  false,
	},
}

// Model aliases: short name → full model ID.
var modelAliases = map[string]string{
	// Short aliases
	"pickle":     "big-pickle",
	"big-pickle": "big-pickle",
	"deepseek":   "deepseek-v4-flash-free",
	"deepseek-v4": "deepseek-v4-flash-free",
	"ds":         "deepseek-v4-flash-free",
	"mimo":       "mimo-v2.5-free",
	"mimo-v2.5":  "mimo-v2.5-free",
	"xiaomi":     "mimo-v2.5-free",
	"north":      "north-mini-code-free",
	"north-mini": "north-mini-code-free",
	"cohere":     "north-mini-code-free",
	"nemotron":   "nemotron-3-ultra-free",
	"nemotron-3": "nemotron-3-ultra-free",
	"nvidia":     "nemotron-3-ultra-free",

	// Claude model name aliases (for Claude Code compatibility)
	// Claude Code validates model names client-side; set ANTHROPIC_MODEL to a Claude name.
	"claude-sonnet-4-6":   "deepseek-v4-flash-free",
	"claude-sonnet-4-5":   "deepseek-v4-flash-free",
	"claude-sonnet-4":     "deepseek-v4-flash-free",
	"claude-opus-4-8":     "deepseek-v4-flash-free",
	"claude-opus-4-5":     "deepseek-v4-flash-free",
	"claude-opus-4":       "deepseek-v4-flash-free",
	"claude-haiku-4-5":    "north-mini-code-free",
	"claude-haiku-4":      "north-mini-code-free",
	"claude-3.5-sonnet":   "north-mini-code-free",
	"claude-3.5-haiku":    "big-pickle",
}

// ModelInfo describes a single model.
type ModelInfo struct {
	ID              string `json:"id"`
	Name            string `json:"name,omitempty"`
	OwnedBy         string `json:"owned_by"`
	ContextWindow   int    `json:"context_window"`
	MaxOutputTokens int    `json:"max_output_tokens"`
	Description     string `json:"description"`
	SupportsVision  bool   `json:"supports_vision"`
}

// Proxy handles forwarding OpenAI-format requests to OpenCode Zen.
type Proxy struct {
	apiKey   string
	sessions map[string]*session // keyed by client-provided API key
	mu       sync.Mutex
}

type session struct {
	id        string
	expiresAt time.Time
}

// NewProxy creates a new Proxy instance.
func NewProxy(apiKey string) *Proxy {
	return &Proxy{
		apiKey:   apiKey,
		sessions: make(map[string]*session),
	}
}

// APIKey returns the configured API key (empty = no auth).
func (p *Proxy) APIKey() string { return p.apiKey }

// Models returns the list of available free models.
func (p *Proxy) Models() []ModelInfo { return zenModels }

// ModelByID returns the ModelInfo entry for a given model ID, or nil if not found.
func ModelByID(id string) *ModelInfo {
	for _, m := range zenModels {
		if m.ID == id {
			return &m
		}
	}
	return nil
}

// ResolveModel maps a requested model name to a Zen model ID.
// Returns the resolved model ID and whether it was found.
func (p *Proxy) ResolveModel(requested string) (string, bool) {
	// Check aliases first (covers both short names and exact IDs)
	if mapped, ok := modelAliases[requested]; ok {
		return mapped, true
	}
	// Check if it's already a valid model ID (belt and suspenders)
	for _, m := range zenModels {
		if m.ID == requested {
			return requested, true
		}
	}
	// Pass through unknown models (might be newly added upstream)
	return requested, false
}

// ZenChatURL returns the full upstream URL for chat completions.
func ZenChatURL() string {
	return ZenBaseURL + "/chat/completions"
}

// ZenModelsURL returns the full upstream URL for model listing.
func ZenModelsURL() string {
	return ZenBaseURL + "/models"
}

// SessionID returns a session ID for the given user key, rotating every 30 minutes.
func (p *Proxy) SessionID(userKey string) string {
	p.mu.Lock()
	defer p.mu.Unlock()

	if s, ok := p.sessions[userKey]; ok && time.Now().Before(s.expiresAt) {
		return s.id
	}

	p.sessions[userKey] = &session{
		id:        "ses_" + randomHex(12),
		expiresAt: time.Now().Add(30 * time.Minute),
	}
	return p.sessions[userKey].id
}

// RequestID generates a new unique request ID.
func RequestID() string {
	return "msg_" + randomHex(12)
}

func randomHex(n int) string {
	b := make([]byte, n)
	rand.Read(b)
	return hex.EncodeToString(b)
}