package contracts

import "errors"

// ErrInvalidStructuredOutput identifies a provider response that cannot satisfy
// the caller's declared structured-output contract.
var ErrInvalidStructuredOutput = errors.New("invalid structured output")

// ErrLLMCapacityExceeded identifies backend admission exhaustion before model
// generation begins.
var ErrLLMCapacityExceeded = errors.New("LLM capacity exceeded")

// ErrLLMGeneration identifies a provider generation failure.
var ErrLLMGeneration = errors.New("LLM generation failed")

type LLMGenerationFailureKind string

const (
	LLMGenerationFailureGeneration        LLMGenerationFailureKind = "generation"
	LLMGenerationFailureTransport         LLMGenerationFailureKind = "transport"
	LLMGenerationFailureProviderStatus    LLMGenerationFailureKind = "provider_status"
	LLMGenerationFailureMalformedResponse LLMGenerationFailureKind = "malformed_response"
)

type LLMGenerationMetadata struct {
	FailureKind      LLMGenerationFailureKind
	RetriesExhausted bool
	Attempts         uint64
}

type LLMGenerationError struct {
	status      int
	diagnostic  string
	failureKind LLMGenerationFailureKind
	exhausted   bool
	attempts    uint64
}

func NewLLMGenerationError(status int, diagnostic string) *LLMGenerationError {
	return NewLLMGenerationErrorWithMetadata(status, diagnostic, LLMGenerationMetadata{})
}

func NewLLMGenerationErrorWithMetadata(status int, diagnostic string, metadata LLMGenerationMetadata) *LLMGenerationError {
	if status < 0 {
		status = 0
	}
	kind := metadata.FailureKind
	if kind == "" {
		kind = LLMGenerationFailureGeneration
	}
	return &LLMGenerationError{status: status, diagnostic: diagnostic, failureKind: kind, exhausted: metadata.RetriesExhausted, attempts: metadata.Attempts}
}
func (e *LLMGenerationError) Error() string {
	if e == nil || e.diagnostic == "" {
		return ErrLLMGeneration.Error()
	}
	return e.diagnostic
}
func (e *LLMGenerationError) Unwrap() error { return ErrLLMGeneration }
func (e *LLMGenerationError) StatusCode() int {
	if e == nil {
		return 0
	}
	return e.status
}

func (e *LLMGenerationError) FailureKind() LLMGenerationFailureKind {
	if e == nil || e.failureKind == "" {
		return LLMGenerationFailureGeneration
	}
	return e.failureKind
}

func (e *LLMGenerationError) RetriesExhausted() bool {
	return e != nil && e.exhausted
}

func (e *LLMGenerationError) Attempts() uint64 {
	if e == nil {
		return 0
	}
	return e.attempts
}