package providers

import (
	"context"
	"fmt"
)

type ToolCall struct {
	ID        string                 `json:"id"`
	Type      string                 `json:"type,omitempty"`
	Function  *FunctionCall          `json:"function,omitempty"`
	Name      string                 `json:"name,omitempty"`
	Arguments map[string]interface{} `json:"arguments,omitempty"`
}

type FunctionCall struct {
	Name      string `json:"name"`
	Arguments string `json:"arguments"`
}

type LLMResponse struct {
	Content      string     `json:"content"`
	ToolCalls    []ToolCall `json:"tool_calls,omitempty"`
	FinishReason string     `json:"finish_reason"`
	Usage        *UsageInfo `json:"usage,omitempty"`
}

type UsageInfo struct {
	PromptTokens     int `json:"prompt_tokens"`
	CompletionTokens int `json:"completion_tokens"`
	TotalTokens      int `json:"total_tokens"`
}

type Message struct {
	Role       string     `json:"role"`
	Content    string     `json:"content"`
	ToolCalls  []ToolCall `json:"tool_calls,omitempty"`
	ToolCallID string     `json:"tool_call_id,omitempty"`
}

type LLMProvider interface {
	Chat(ctx context.Context, messages []Message, tools []ToolDefinition, model string, options map[string]interface{}) (*LLMResponse, error)
	GetDefaultModel() string
}

// FailoverReason classifies why an LLM request failed for fallback decisions.
type FailoverReason string

const (
	FailoverAuth       FailoverReason = "auth"
	FailoverRateLimit  FailoverReason = "rate_limit"
	FailoverBilling    FailoverReason = "billing"
	FailoverTimeout    FailoverReason = "timeout"
	FailoverFormat     FailoverReason = "format"
	FailoverOverloaded FailoverReason = "overloaded"
	FailoverUnknown    FailoverReason = "unknown"
)

// FailoverError wraps an LLM provider error with classification metadata.
type FailoverError struct {
	Reason   FailoverReason
	Provider string
	Model    string
	Status   int
	Wrapped  error
}

func (e *FailoverError) Error() string {
	return fmt.Sprintf("failover(%s): provider=%s model=%s status=%d: %v",
		e.Reason, e.Provider, e.Model, e.Status, e.Wrapped)
}

func (e *FailoverError) Unwrap() error {
	return e.Wrapped
}

// IsRetriable returns true if this error should trigger fallback to next candidate.
// Non-retriable: Format errors (bad request structure, image dimension/size).
func (e *FailoverError) IsRetriable() bool {
	return e.Reason != FailoverFormat
}

// ModelConfig holds primary model and fallback list.
type ModelConfig struct {
	Primary   string
	Fallbacks []string
}

type ToolDefinition struct {
	Type     string                 `json:"type"`
	Function ToolFunctionDefinition `json:"function"`
}

type ToolFunctionDefinition struct {
	Name        string                 `json:"name"`
	Description string                 `json:"description"`
	Parameters  map[string]interface{} `json:"parameters"`
}