refactor: improve thinking logic

internal/thinking/suffix.go

@@ -0,0 +1,170 @@
+// Package thinking provides unified thinking configuration processing.
+//
+// This file implements suffix parsing functionality for extracting
+// thinking configuration from model names in the format model(value).
+package thinking
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// ParseSuffix extracts thinking suffix from a model name.
+//
+// The suffix format is: model-name(value)
+// Examples:
+//   - "claude-sonnet-4-5(16384)" -> ModelName="claude-sonnet-4-5", RawSuffix="16384"
+//   - "gpt-5.2(high)" -> ModelName="gpt-5.2", RawSuffix="high"
+//   - "gemini-2.5-pro" -> ModelName="gemini-2.5-pro", HasSuffix=false
+//
+// This function only extracts the suffix; it does not validate or interpret
+// the suffix content. Use ParseNumericSuffix, ParseLevelSuffix, etc. for
+// content interpretation.
+func ParseSuffix(model string) SuffixResult {
+	// Find the last opening parenthesis
+	lastOpen := strings.LastIndex(model, "(")
+	if lastOpen == -1 {
+		return SuffixResult{ModelName: model, HasSuffix: false}
+	}
+
+	// Check if the string ends with a closing parenthesis
+	if !strings.HasSuffix(model, ")") {
+		return SuffixResult{ModelName: model, HasSuffix: false}
+	}
+
+	// Extract components
+	modelName := model[:lastOpen]
+	rawSuffix := model[lastOpen+1 : len(model)-1]
+
+	return SuffixResult{
+		ModelName: modelName,
+		HasSuffix: true,
+		RawSuffix: rawSuffix,
+	}
+}
+
+// ParseSuffixWithError extracts thinking suffix and returns an error on invalid format.
+//
+// Invalid format cases:
+//   - Contains "(" but does not end with ")"
+//   - Contains ")" without any "("
+//
+// The error message includes the original input for debugging context.
+func ParseSuffixWithError(model string) (SuffixResult, error) {
+	lastOpen := strings.LastIndex(model, "(")
+	if lastOpen == -1 {
+		if strings.Contains(model, ")") {
+			return SuffixResult{ModelName: model, HasSuffix: false}, NewThinkingError(ErrInvalidSuffix, fmt.Sprintf("invalid suffix format: %s", model))
+		}
+		return SuffixResult{ModelName: model, HasSuffix: false}, nil
+	}
+
+	if !strings.HasSuffix(model, ")") {
+		return SuffixResult{ModelName: model, HasSuffix: false}, NewThinkingError(ErrInvalidSuffix, fmt.Sprintf("invalid suffix format: %s", model))
+	}
+
+	return ParseSuffix(model), nil
+}
+
+// ParseNumericSuffix attempts to parse a raw suffix as a numeric budget value.
+//
+// This function parses the raw suffix content (from ParseSuffix.RawSuffix) as an integer.
+// Only non-negative integers are considered valid numeric suffixes.
+//
+// Platform note: The budget value uses Go's int type, which is 32-bit on 32-bit
+// systems and 64-bit on 64-bit systems. Values exceeding the platform's int range
+// will return ok=false.
+//
+// Leading zeros are accepted: "08192" parses as 8192.
+//
+// Examples:
+//   - "8192" -> budget=8192, ok=true
+//   - "0" -> budget=0, ok=true (represents ModeNone)
+//   - "08192" -> budget=8192, ok=true (leading zeros accepted)
+//   - "-1" -> budget=0, ok=false (negative numbers are not valid numeric suffixes)
+//   - "high" -> budget=0, ok=false (not a number)
+//   - "9223372036854775808" -> budget=0, ok=false (overflow on 64-bit systems)
+//
+// For special handling of -1 as auto mode, use ParseSpecialSuffix instead.
+func ParseNumericSuffix(rawSuffix string) (budget int, ok bool) {
+	if rawSuffix == "" {
+		return 0, false
+	}
+
+	value, err := strconv.Atoi(rawSuffix)
+	if err != nil {
+		return 0, false
+	}
+
+	// Negative numbers are not valid numeric suffixes
+	// -1 should be handled by special value parsing as "auto"
+	if value < 0 {
+		return 0, false
+	}
+
+	return value, true
+}
+
+// ParseSpecialSuffix attempts to parse a raw suffix as a special thinking mode value.
+//
+// This function handles special strings that represent a change in thinking mode:
+//   - "none" -> ModeNone (disables thinking)
+//   - "auto" -> ModeAuto (automatic/dynamic thinking)
+//   - "-1"   -> ModeAuto (numeric representation of auto mode)
+//
+// String values are case-insensitive.
+func ParseSpecialSuffix(rawSuffix string) (mode ThinkingMode, ok bool) {
+	if rawSuffix == "" {
+		return ModeBudget, false
+	}
+
+	// Case-insensitive matching
+	switch strings.ToLower(rawSuffix) {
+	case "none":
+		return ModeNone, true
+	case "auto", "-1":
+		return ModeAuto, true
+	default:
+		return ModeBudget, false
+	}
+}
+
+// ParseLevelSuffix attempts to parse a raw suffix as a discrete thinking level.
+//
+// This function parses the raw suffix content (from ParseSuffix.RawSuffix) as a level.
+// Only discrete effort levels are valid: minimal, low, medium, high, xhigh.
+// Level matching is case-insensitive.
+//
+// Special values (none, auto) are NOT handled by this function; use ParseSpecialSuffix
+// instead. This separation allows callers to prioritize special value handling.
+//
+// Examples:
+//   - "high" -> level=LevelHigh, ok=true
+//   - "HIGH" -> level=LevelHigh, ok=true (case insensitive)
+//   - "medium" -> level=LevelMedium, ok=true
+//   - "none" -> level="", ok=false (special value, use ParseSpecialSuffix)
+//   - "auto" -> level="", ok=false (special value, use ParseSpecialSuffix)
+//   - "8192" -> level="", ok=false (numeric, use ParseNumericSuffix)
+//   - "ultra" -> level="", ok=false (unknown level)
+func ParseLevelSuffix(rawSuffix string) (level ThinkingLevel, ok bool) {
+	if rawSuffix == "" {
+		return "", false
+	}
+
+	// Case-insensitive matching
+	switch strings.ToLower(rawSuffix) {
+	case "minimal":
+		return LevelMinimal, true
+	case "low":
+		return LevelLow, true
+	case "medium":
+		return LevelMedium, true
+	case "high":
+		return LevelHigh, true
+	case "xhigh":
+		return LevelXHigh, true
+	default:
+		return "", false
+	}
+}