package providers

import (
	"context"
	"encoding/json"
	"errors"
	"log"
	"net/http"
	"net/url"
	"sync"
	"time"

	"chat-switchboard/models"
)

// ── Errors ─────────────────────────────────

var ErrNotSupported = errors.New("operation not supported by this provider")

// ── Provider Interface ──────────────────────

// Provider is the contract for LLM API adapters.
type Provider interface {
	// ID returns the provider identifier (e.g. "openai", "anthropic").
	ID() string

	// ChatCompletion sends a non-streaming request and returns the full response.
	ChatCompletion(ctx context.Context, cfg ProviderConfig, req CompletionRequest) (*CompletionResponse, error)

	// StreamCompletion sends a streaming request and returns a channel of events.
	// The channel is closed when the stream ends. Errors are sent as StreamEvents.
	StreamCompletion(ctx context.Context, cfg ProviderConfig, req CompletionRequest) (<-chan StreamEvent, error)

	// ListModels returns available models from this provider.
	ListModels(ctx context.Context, cfg ProviderConfig) ([]Model, error)

	// Embed generates embeddings for the given input texts.
	// Returns ErrNotSupported if the provider has no embedding endpoint.
	Embed(ctx context.Context, cfg ProviderConfig, req EmbeddingRequest) (*EmbeddingResponse, error)
}

// ── Configuration ───────────────────────────

// ProviderConfig holds credentials and endpoint for a configured provider.
// Populated from the provider_configs table at call time.
type ProviderConfig struct {
	Endpoint      string
	APIKey        string
	CustomHeaders map[string]string      // Extra HTTP headers (e.g. OpenRouter HTTP-Referer)
	Settings      map[string]interface{} // Provider-specific settings from config JSONB
	ProxyMode     string                 // "system" (default), "direct", "custom"
	ProxyURL      string                 // Only used when ProxyMode == "custom"
}

// ── HTTP Client Pool ───────────────────────
//
// Provider HTTP clients are pooled by (ProxyMode, ProxyURL) tuple.
// Previously Client() created a new http.Transport per call, leaking
// idle connections and preventing TCP reuse across requests to the same
// provider. With pooling, a Venice model sync followed by a completion
// reuses the same TCP connection to api.venice.ai.

// clientPool holds shared *http.Client instances keyed by proxy config.
var clientPool sync.Map // map[string]*http.Client

// Client returns an *http.Client configured for this provider's proxy settings.
// Clients are cached and reused across calls with the same proxy configuration.
// system = http.ProxyFromEnvironment (Go default), direct = no proxy,
// custom = explicit proxy URL (http/https/socks5).
func (c ProviderConfig) Client() *http.Client {
	key := c.ProxyMode + "|" + c.ProxyURL
	if v, ok := clientPool.Load(key); ok {
		return v.(*http.Client)
	}

	transport := &http.Transport{
		MaxIdleConns:        100,
		MaxIdleConnsPerHost: 10,
		IdleConnTimeout:     90 * time.Second,
		TLSHandshakeTimeout: 10 * time.Second,
	}
	switch c.ProxyMode {
	case "direct":
		transport.Proxy = nil
	case "custom":
		if c.ProxyURL != "" {
			u, err := url.Parse(c.ProxyURL)
			if err != nil {
				// Fall back to system rather than silently going direct —
				// a bad custom URL in a mandatory-proxy environment is a
				// security/audit hole if it silently bypasses.
				log.Printf("[proxy] invalid custom proxy URL %q: %v — falling back to system proxy", c.ProxyURL, err)
				transport.Proxy = http.ProxyFromEnvironment
			} else {
				transport.Proxy = http.ProxyURL(u)
			}
		} else {
			transport.Proxy = http.ProxyFromEnvironment
		}
	default: // "system" or empty
		transport.Proxy = http.ProxyFromEnvironment
	}

	client := &http.Client{Transport: transport}
	actual, _ := clientPool.LoadOrStore(key, client)
	return actual.(*http.Client)
}

// ── Request / Response Types ────────────────

// Message represents a chat message in the conversation.
type Message struct {
	Role    string `json:"role"`    // user, assistant, system, tool
	Content string `json:"content"`

	// Multimodal content parts (v0.12.0+). When set, providers use these
	// instead of Content for the user message. Content is still set as
	// a fallback and for message persistence (extracted text summary).
	ContentParts []ContentPart `json:"content_parts,omitempty"`

	// Tool calling fields (assistant → tool_calls, tool → tool_call_id)
	ToolCalls  []ToolCall `json:"tool_calls,omitempty"`   // set when assistant requests tools
	ToolCallID string     `json:"tool_call_id,omitempty"` // set for role="tool" result messages
	Name       string     `json:"name,omitempty"`         // speaker name (tool result, or persona attribution v0.23.0)
}

// ContentPart is a single element in a multimodal message.
// Providers convert these to their native wire format.
type ContentPart struct {
	Type string `json:"type"` // "text", "image_url", "document"

	// Text content (type="text")
	Text string `json:"text,omitempty"`

	// Image content (type="image_url") — base64 data URI
	ImageURL *ImageURL `json:"image_url,omitempty"`
}

// ImageURL holds image data for multimodal requests.
// URL is a data URI: "data:image/jpeg;base64,..."
type ImageURL struct {
	URL    string `json:"url"`
	Detail string `json:"detail,omitempty"` // "auto", "low", "high"
}

// ToolCall represents a function call requested by the LLM.
type ToolCall struct {
	ID       string       `json:"id"`
	Type     string       `json:"type"` // "function"
	Function FunctionCall `json:"function"`
}

// FunctionCall is the function name and JSON arguments.
type FunctionCall struct {
	Name      string `json:"name"`
	Arguments string `json:"arguments"`
}

// ToolDef describes a tool available to the LLM.
type ToolDef struct {
	Type     string      `json:"type"` // "function"
	Function FunctionDef `json:"function"`
}

// FunctionDef is the schema for a tool function.
type FunctionDef struct {
	Name        string          `json:"name"`
	Description string          `json:"description"`
	Parameters  json.RawMessage `json:"parameters"`
}

// CompletionRequest is the normalized request sent to any provider.
type CompletionRequest struct {
	Model       string                 `json:"model"`
	Messages    []Message              `json:"messages"`
	MaxTokens   int                    `json:"max_tokens,omitempty"`
	Temperature *float64               `json:"temperature,omitempty"`
	TopP        *float64               `json:"top_p,omitempty"`
	Stream      bool                   `json:"stream,omitempty"`
	Tools       []ToolDef              `json:"tools,omitempty"`       // available tools for function calling
	ExtraBody   map[string]interface{} `json:"-"`                     // provider-specific wire fields (v0.22.1)
}

// CompletionResponse is the normalized non-streaming response.
type CompletionResponse struct {
	Content             string     `json:"content"`
	Model               string     `json:"model"`
	FinishReason        string     `json:"finish_reason"`
	InputTokens         int        `json:"input_tokens"`
	OutputTokens        int        `json:"output_tokens"`
	CacheCreationTokens int        `json:"cache_creation_tokens,omitempty"`
	CacheReadTokens     int        `json:"cache_read_tokens,omitempty"`
	ToolCalls           []ToolCall `json:"tool_calls,omitempty"` // set when finish_reason is "tool_calls"
}

// StreamEvent is a single chunk from a streaming response.
type StreamEvent struct {
	Delta               string     `json:"delta,omitempty"`
	Reasoning           string     `json:"reasoning,omitempty"`
	Done                bool       `json:"done,omitempty"`
	FinishReason        string     `json:"finish_reason,omitempty"`
	ToolCalls           []ToolCall `json:"tool_calls,omitempty"`
	Model               string     `json:"model,omitempty"`
	Error               error      `json:"-"`
	InputTokens         int        `json:"input_tokens,omitempty"`
	OutputTokens        int        `json:"output_tokens,omitempty"`
	CacheCreationTokens int        `json:"cache_creation_tokens,omitempty"`
	CacheReadTokens     int        `json:"cache_read_tokens,omitempty"`
}

// ── Embedding Types ────────────────────────

// EmbeddingRequest is the normalized embedding request.
type EmbeddingRequest struct {
	Model string   `json:"model"`
	Input []string `json:"input"` // batch of texts to embed
}

// EmbeddingResponse is the normalized embedding response.
type EmbeddingResponse struct {
	Embeddings  [][]float64 `json:"embeddings"`
	Model       string      `json:"model"`
	InputTokens int         `json:"input_tokens"`
}

// Model represents an available model from a provider, with capabilities.
type Model struct {
	ID           string                   `json:"id"`
	Name         string                   `json:"name,omitempty"`
	Type         string                   `json:"type,omitempty"` // "chat", "embedding", "image" — from provider API
	OwnedBy      string                   `json:"owned_by,omitempty"`
	Capabilities models.ModelCapabilities `json:"capabilities"`
	Pricing      *models.ModelPricing     `json:"pricing,omitempty"`
}

// mergeExtraBody merges arbitrary key-value pairs into a marshalled JSON object.
// Used by provider doRequest methods to inject hook-supplied fields (e.g.
// venice_parameters, thinking config) into the wire-format request body.
func mergeExtraBody(body []byte, extra map[string]interface{}) ([]byte, error) {
	var base map[string]interface{}
	if err := json.Unmarshal(body, &base); err != nil {
		return nil, err
	}
	for k, v := range extra {
		base[k] = v
	}
	return json.Marshal(base)
}