// Copyright 2026 Alibaba Group
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package handlers

import (
	"github.com/DingTalk-Real-AI/dingtalk-workspace-cli/internal/pipeline"
	"github.com/DingTalk-Real-AI/dingtalk-workspace-cli/pkg/cmdutil"
)

// ParamNameHandler performs fuzzy correction on flag names that are
// not recognised after alias normalisation. It uses Levenshtein edit
// distance to find the closest known flag name, with a conservative
// threshold to avoid false positives.
//
// Correction rules:
//   - Edit distance must be ≤ maxEditDistance (default 2).
//   - The match must be unambiguous (exactly one candidate within threshold).
//   - Very short flag names (≤ 3 chars) use a tighter threshold of 1.
//
// This handler should run after AliasHandler in the PreParse phase
// so that obvious normalisation (camelCase → kebab-case) is already
// done and fuzzy matching only handles genuine near-misses.
type ParamNameHandler struct{}

func (ParamNameHandler) Name() string          { return "paramname" }
func (ParamNameHandler) Phase() pipeline.Phase { return pipeline.PreParse }

func (ParamNameHandler) Handle(ctx *pipeline.Context) error {
	if len(ctx.Args) == 0 || len(ctx.FlagSpecs) == 0 {
		return nil
	}

	known := buildFlagSet(ctx.FlagSpecs)
	names := make([]string, 0, len(ctx.FlagSpecs))
	for _, spec := range ctx.FlagSpecs {
		if spec.Name != "" {
			names = append(names, spec.Name)
		}
	}

	result := make([]string, 0, len(ctx.Args))
	for i, arg := range ctx.Args {
		if arg == "--" {
			result = append(result, ctx.Args[i:]...)
			break
		}
		if bare, _, isFlag := splitFlagToken(arg); isFlag && ctx.IsFlagProtected(cmdutil.Morph(bare)) {
			result = append(result, arg)
			continue
		}
		rewritten, ok := tryFuzzyMatch(arg, known, names)
		if ok {
			ctx.AddCorrection("paramname", pipeline.PreParse, rewritten, arg, rewritten, "fuzzy")
			result = append(result, rewritten)
		} else {
			result = append(result, arg)
		}
	}

	ctx.Args = result
	return nil
}

// tryFuzzyMatch attempts to correct an unrecognised "--flag" token by
// finding the closest known flag name within the edit distance threshold.
func tryFuzzyMatch(arg string, known map[string]bool, candidates []string) (string, bool) {
	return pipeline.FuzzyMatchFlag(arg, known, candidates)
}