package providers

import (
	"context"
	"encoding/json"
)

// ── 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)
}

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

// ProviderConfig holds credentials and endpoint for a configured provider.
// Populated from the api_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 provider_settings JSONB
}

// ── 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"`

	// 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"`         // tool name for role="tool"
}

// 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
}

// 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"`
	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 is the incremental text content (empty for non-content events).
	Delta string `json:"delta,omitempty"`

	// Done is true when the stream is complete.
	Done bool `json:"done,omitempty"`

	// FinishReason is set on the final event.
	// "stop" = normal, "tool_calls" = LLM wants to call tools.
	FinishReason string `json:"finish_reason,omitempty"`

	// ToolCalls accumulates tool call data during streaming.
	// Fully populated on the final event when FinishReason is "tool_calls".
	ToolCalls []ToolCall `json:"tool_calls,omitempty"`

	// Model echoes back the model used.
	Model string `json:"model,omitempty"`

	// Error is set if the stream encountered an error.
	Error error `json:"-"`
}

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

// ModelPricing holds per-million-token costs.
type ModelPricing struct {
	InputPerM  float64 `json:"input_per_m,omitempty"`
	OutputPerM float64 `json:"output_per_m,omitempty"`
}