package proxy

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"sync"
	"time"
)

// KiloGatewayBase is the Kilo Code public gateway base URL.
// Confirmed working without auth for free models (HTTP 200 on both
// GET /api/gateway/models and POST /api/gateway/chat/completions).
const KiloGatewayBase = "https://api.kilo.ai/api/gateway"

// KiloBackend forwards to Kilo Code's free gateway models.
//
// Kilo is an opencode-based CLI whose gateway exposes free models (flagged
// isFree:true in GET /api/gateway/models) reachable without authentication,
// in standard OpenAI Chat Completions format. This backend is a Discoverer:
// it auto-discovers its full free catalogue with rich metadata from the
// upstream /models endpoint.
type KiloBackend struct {
	mu         sync.RWMutex
	discovered []ModelInfo
}

// kiloCuratedModels is the curated base layer: aliases + trusted metadata.
// Discovered models matching these IDs keep this metadata (curated wins).
// Discovered-only models use the metadata parsed from the upstream response.
var kiloCuratedModels = []ModelInfo{
	{
		ID:              "stepfun/step-3.7-flash:free",
		Name:            "StepFun Step 3.7 Flash (Free)",
		OwnedBy:         "stepfun",
		ContextWindow:   256_000,
		MaxOutputTokens: 32_000,
		Description:     "StepFun. Flash rápido, tareas generales.",
	},
	{
		ID:              "poolside/laguna-m.1:free",
		Name:            "Poolside Laguna M.1 (Free)",
		OwnedBy:         "poolside",
		ContextWindow:   256_000,
		MaxOutputTokens: 32_000,
		Description:     "Poolside. Modelo orientado a código.",
	},
	{
		ID:              "nvidia/nemotron-3-ultra-550b-a55b:free",
		Name:            "Nemotron 3 Ultra 550B (Free)",
		OwnedBy:         "nvidia",
		ContextWindow:   1_000_000,
		MaxOutputTokens: 16_384,
		Description:     "NVIDIA Nemotron 3 Ultra (550B/55B MoE). 1M contexto, razonamiento.",
	},
	{
		ID:              "openrouter/free",
		Name:            "OpenRouter Best Free (Free)",
		OwnedBy:         "openrouter",
		ContextWindow:   256_000,
		MaxOutputTokens: 32_000,
		Description:     "OpenRouter selecciona automáticamente el mejor modelo free disponible.",
	},
}

// kiloAliases lets clients use shorter names for Kilo free models.
var kiloAliases = map[string]string{
	"stepfun":       "stepfun/step-3.7-flash:free",
	"stepfun-free":  "stepfun/step-3.7-flash:free",
	"poolside":      "poolside/laguna-m.1:free",
	"poolside-free": "poolside/laguna-m.1:free",
	"laguna":        "poolside/laguna-m.1:free",
	"openrouter":    "openrouter/free",
}

// Name returns the backend identifier.
func (*KiloBackend) Name() string { return "kilo" }

// Models returns the Kilo free models (discovered catalogue, or curated
// fallback before the first successful Refresh()).
func (b *KiloBackend) Models() []ModelInfo {
	b.mu.RLock()
	defer b.mu.RUnlock()
	if len(b.discovered) == 0 {
		return kiloCuratedModels
	}
	return b.discovered
}

// Resolve maps a requested name to a Kilo model ID. Checks curated aliases,
// curated IDs, then the discovered catalogue so newly discovered models route
// correctly instead of falling through to pass-through.
func (b *KiloBackend) Resolve(model string) (string, bool) {
	if mapped, ok := kiloAliases[model]; ok {
		return mapped, true
	}
	for _, m := range kiloCuratedModels {
		if m.ID == model {
			return model, true
		}
	}
	b.mu.RLock()
	defer b.mu.RUnlock()
	for _, m := range b.discovered {
		if m.ID == model {
			return model, true
		}
	}
	return "", false
}

// ChatURL is the Kilo gateway chat completions endpoint.
func (*KiloBackend) ChatURL() string { return KiloGatewayBase + "/chat/completions" }

// Headers returns minimal headers for the Kilo gateway (no auth needed for free).
func (*KiloBackend) Headers(_, _ string) map[string]string {
	return map[string]string{
		"Content-Type": "application/json",
		"Accept":       "text/event-stream, application/json",
		"User-Agent":   "kilo/7.3.54",
	}
}

// ---------- Auto-discovery ----------

// Refresh fetches GET /api/gateway/models, keeps only isFree:true entries,
// and merges them with the curated base layer. Curated metadata wins for
// known IDs; discovered-only models use upstream metadata.
func (b *KiloBackend) Refresh() error {
	req, err := http.NewRequest("GET", KiloGatewayBase+"/models", nil)
	if err != nil {
		return err
	}
	req.Header.Set("User-Agent", "kilo/7.3.54")
	req.Header.Set("Accept", "application/json")

	client := &http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("kilo discovery: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		return fmt.Errorf("kilo discovery: upstream status %d", resp.StatusCode)
	}
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return err
	}

	parsed := parseKiloModels(body)

	merged := mergeKiloCatalogue(kiloCuratedModels, parsed)

	b.mu.Lock()
	b.discovered = merged
	b.mu.Unlock()
	return nil
}

// kiloModelsResponse is the subset of the Kilo /models schema we care about.
type kiloModelsResponse struct {
	Data []struct {
		ID          string `json:"id"`
		Name        string `json:"name"`
		Description string `json:"description"`
		IsFree      bool   `json:"isFree"`
		ContextLen  int    `json:"context_length"`
		TopProvider struct {
			ContextLength      int   `json:"context_length"`
			MaxCompletionTokens *int `json:"max_completion_tokens"`
		} `json:"top_provider"`
		Architecture struct {
			InputModalities []string `json:"input_modalities"`
		} `json:"architecture"`
		Pricing struct {
			Prompt     string `json:"prompt"`
			Completion string `json:"completion"`
		} `json:"pricing"`
	} `json:"data"`
}

// parseKiloModels converts the upstream response into ModelInfo entries,
// keeping only free models (isFree:true).
func parseKiloModels(body []byte) []ModelInfo {
	var resp kiloModelsResponse
	if err := json.Unmarshal(body, &resp); err != nil {
		return nil
	}
	var out []ModelInfo
	for _, m := range resp.Data {
		if !m.IsFree {
			continue
		}
		ctx := m.ContextLen
		if ctx == 0 {
			ctx = m.TopProvider.ContextLength
		}
		maxOut := 0
		if m.TopProvider.MaxCompletionTokens != nil {
			maxOut = *m.TopProvider.MaxCompletionTokens
		}
		vision := false
		for _, mod := range m.Architecture.InputModalities {
			if mod == "image" {
				vision = true
			}
		}
		owner := ownerFromID(m.ID)
		desc := m.Description
		if desc == "" {
			desc = fmt.Sprintf("%s (free). Detectado automáticamente.", m.Name)
		}
		out = append(out, ModelInfo{
			ID:              m.ID,
			Name:            m.Name,
			OwnedBy:         owner,
			ContextWindow:   ctx,
			MaxOutputTokens: maxOut,
			Description:     desc,
			SupportsVision:  vision,
		})
	}
	return out
}

// mergeKiloCatalogue merges curated + discovered. Curated entries are always
// present (with their metadata). Discovered entries not in curated are added.
func mergeKiloCatalogue(curated, discovered []ModelInfo) []ModelInfo {
	byID := make(map[string]bool, len(curated)+len(discovered))
	merged := make([]ModelInfo, 0, len(curated)+len(discovered))
	// Curated first (trusted metadata + aliases still resolve).
	for _, m := range curated {
		if !byID[m.ID] {
			merged = append(merged, m)
			byID[m.ID] = true
		}
	}
	// Discovered-only appended with upstream metadata.
	for _, m := range discovered {
		if !byID[m.ID] {
			merged = append(merged, m)
			byID[m.ID] = true
		}
	}
	return merged
}

// ownerFromID extracts a provider name from a "provider/model" id.
func ownerFromID(id string) string {
	if i := strings.Index(id, "/"); i >= 0 {
		return id[:i]
	}
	return "unknown"
}