package thinking

import (
	"fmt"
	"strings"

	"github.com/router-for-me/CLIProxyAPI/v6/internal/registry"
)

// levelToBudgetMap defines the standard Level → Budget mapping.
// All keys are lowercase; lookups should use strings.ToLower.
var levelToBudgetMap = map[string]int{
	"none":    0,
	"auto":    -1,
	"minimal": 512,
	"low":     1024,
	"medium":  8192,
	"high":    24576,
	"xhigh":   32768,
}

// ConvertLevelToBudget converts a thinking level to a budget value.
//
// This is a semantic conversion that maps discrete levels to numeric budgets.
// Level matching is case-insensitive.
//
// Level → Budget mapping:
//   - none    → 0
//   - auto    → -1
//   - minimal → 512
//   - low     → 1024
//   - medium  → 8192
//   - high    → 24576
//   - xhigh   → 32768
//
// Returns:
//   - budget: The converted budget value
//   - ok: true if level is valid, false otherwise
func ConvertLevelToBudget(level string) (int, bool) {
	budget, ok := levelToBudgetMap[strings.ToLower(level)]
	return budget, ok
}

// BudgetThreshold constants define the upper bounds for each thinking level.
// These are used by ConvertBudgetToLevel for range-based mapping.
const (
	// ThresholdMinimal is the upper bound for "minimal" level (1-512)
	ThresholdMinimal = 512
	// ThresholdLow is the upper bound for "low" level (513-1024)
	ThresholdLow = 1024
	// ThresholdMedium is the upper bound for "medium" level (1025-8192)
	ThresholdMedium = 8192
	// ThresholdHigh is the upper bound for "high" level (8193-24576)
	ThresholdHigh = 24576
)

// ConvertBudgetToLevel converts a budget value to the nearest thinking level.
//
// This is a semantic conversion that maps numeric budgets to discrete levels.
// Uses threshold-based mapping for range conversion.
//
// Budget → Level thresholds:
//   - -1        → auto
//   - 0         → none
//   - 1-512     → minimal
//   - 513-1024  → low
//   - 1025-8192 → medium
//   - 8193-24576 → high
//   - 24577+    → xhigh
//
// Returns:
//   - level: The converted thinking level string
//   - ok: true if budget is valid, false for invalid negatives (< -1)
func ConvertBudgetToLevel(budget int) (string, bool) {
	switch {
	case budget < -1:
		// Invalid negative values
		return "", false
	case budget == -1:
		return string(LevelAuto), true
	case budget == 0:
		return string(LevelNone), true
	case budget <= ThresholdMinimal:
		return string(LevelMinimal), true
	case budget <= ThresholdLow:
		return string(LevelLow), true
	case budget <= ThresholdMedium:
		return string(LevelMedium), true
	case budget <= ThresholdHigh:
		return string(LevelHigh), true
	default:
		return string(LevelXHigh), true
	}
}

// ModelCapability describes the thinking format support of a model.
type ModelCapability int

const (
	// CapabilityUnknown indicates modelInfo is nil (passthrough behavior, internal use).
	CapabilityUnknown ModelCapability = iota - 1
	// CapabilityNone indicates model doesn't support thinking (Thinking is nil).
	CapabilityNone
	// CapabilityBudgetOnly indicates the model supports numeric budgets only.
	CapabilityBudgetOnly
	// CapabilityLevelOnly indicates the model supports discrete levels only.
	CapabilityLevelOnly
	// CapabilityHybrid indicates the model supports both budgets and levels.
	CapabilityHybrid
)

// detectModelCapability determines the thinking format capability of a model.
//
// This is an internal function used by NormalizeForModel to decide conversion strategy.
// It analyzes the model's ThinkingSupport configuration to classify the model:
//   - CapabilityNone: modelInfo.Thinking is nil (model doesn't support thinking)
//   - CapabilityBudgetOnly: Has Min/Max but no Levels (Claude, Gemini 2.5)
//   - CapabilityLevelOnly: Has Levels but no Min/Max (OpenAI, iFlow)
//   - CapabilityHybrid: Has both Min/Max and Levels (Gemini 3)
//
// Note: Returns a special sentinel value when modelInfo itself is nil (unknown model).
func detectModelCapability(modelInfo *registry.ModelInfo) ModelCapability {
	if modelInfo == nil {
		return CapabilityUnknown // sentinel for "passthrough" behavior
	}
	if modelInfo.Thinking == nil {
		return CapabilityNone
	}
	support := modelInfo.Thinking
	hasBudget := support.Min > 0 || support.Max > 0
	hasLevels := len(support.Levels) > 0

	switch {
	case hasBudget && hasLevels:
		return CapabilityHybrid
	case hasBudget:
		return CapabilityBudgetOnly
	case hasLevels:
		return CapabilityLevelOnly
	default:
		return CapabilityNone
	}
}

// normalizeMixedConfig resolves a thinking configuration when both budget and level
// might be present, applying priority rules.
//
// Priority rules (Level takes precedence over Budget):
//   - If level is non-empty: use level (special handling for "auto" and "none")
//   - If level is empty and budget is set: use budget
//   - If neither is set (budget=0, level=""): return ModeNone
//
// This function is used internally to handle ambiguous input configurations.
func normalizeMixedConfig(budget int, level string) ThinkingConfig {
	normalizedLevel := strings.ToLower(strings.TrimSpace(level))
	if normalizedLevel != "" {
		switch normalizedLevel {
		case string(LevelAuto):
			return ThinkingConfig{Mode: ModeAuto, Budget: -1, Level: ThinkingLevel(normalizedLevel)}
		case string(LevelNone):
			return ThinkingConfig{Mode: ModeNone, Budget: 0, Level: ThinkingLevel(normalizedLevel)}
		default:
			return ThinkingConfig{Mode: ModeLevel, Level: ThinkingLevel(normalizedLevel)}
		}
	}
	switch budget {
	case -1:
		return ThinkingConfig{Mode: ModeAuto, Budget: -1}
	case 0:
		return ThinkingConfig{Mode: ModeNone, Budget: 0}
	default:
		return ThinkingConfig{Mode: ModeBudget, Budget: budget}
	}
}

// NormalizeForModel normalizes a thinking configuration for a specific model.
//
// This function converts the configuration format based on model capabilities:
//   - Budget-only models (Claude, Gemini 2.5): Level → Budget conversion
//   - Level-only models (OpenAI, iFlow): Budget → Level conversion
//   - Hybrid models (Gemini 3): preserve the original format
//   - No thinking support (Thinking is nil): degrade to ModeNone
//   - Unknown model (modelInfo is nil): passthrough (preserve original format)
//
// Parameters:
//   - config: The thinking configuration to normalize (must not be nil)
//   - modelInfo: Model registry information containing ThinkingSupport properties
//
// Returns:
//   - Normalized ThinkingConfig suitable for the model
//   - Error if conversion fails (e.g., unsupported level or invalid budget)
func NormalizeForModel(config *ThinkingConfig, modelInfo *registry.ModelInfo) (*ThinkingConfig, error) {
	if config == nil {
		return nil, fmt.Errorf("thinking config is nil")
	}

	normalized := *config
	capability := detectModelCapability(modelInfo)

	// If model doesn't support thinking, degrade to ModeNone
	if capability == CapabilityNone && config.Mode != ModeNone && config.Mode != ModeAuto {
		return &ThinkingConfig{Mode: ModeNone, Budget: 0}, nil
	}

	switch config.Mode {
	case ModeAuto, ModeNone:
		return &normalized, nil
	case ModeBudget:
		if capability == CapabilityLevelOnly {
			level, ok := ConvertBudgetToLevel(config.Budget)
			if !ok {
				return nil, fmt.Errorf("invalid budget: %d", config.Budget)
			}
			normalized.Mode = ModeLevel
			normalized.Level = ThinkingLevel(level)
			normalized.Budget = 0
		}
		return &normalized, nil
	case ModeLevel:
		if capability == CapabilityBudgetOnly {
			budget, ok := ConvertLevelToBudget(string(config.Level))
			if !ok {
				return nil, fmt.Errorf("unknown level: %s", config.Level)
			}
			normalized.Mode = ModeBudget
			normalized.Budget = budget
			normalized.Level = ""
		}
		return &normalized, nil
	default:
		return &normalized, nil
	}
}