package chattool

import (
	"context"
	"encoding/json"
	"strings"

	"charm.land/fantasy"

	"github.com/coder/coder/v2/codersdk/workspacesdk"
)

type EditFilesOptions struct {
	GetWorkspaceConn func(context.Context) (workspacesdk.AgentConn, error)
	ResolvePlanPath  func(context.Context) (chatPath string, home string, err error)
	IsPlanTurn       bool
}

// EditFilesArgs is the tool input schema, auto-generated by the
// fantasy framework from these struct tags.
type EditFilesArgs struct {
	Files []editFileEdits `json:"files"`
}

type editFileEdits struct {
	Path  string         `json:"path"`
	Edits []editFileEdit `json:"edits"`
}

// editFileEdit uses "old_text"/"new_text" instead of "search"/"replace"
// because models confused the direction (CODAGT-312). Deprecated
// "search"/"replace" accepted via UnmarshalJSON; toSDKFiles maps back
// to "search"/"replace" for agent/agentfiles.
type editFileEdit struct {
	OldText    string `json:"old_text"`
	NewText    string `json:"new_text"`
	ReplaceAll bool   `json:"replace_all,omitempty"`
}

// UnmarshalJSON falls back to deprecated "search"/"replace" when
// "old_text"/"new_text" are empty.
func (e *editFileEdit) UnmarshalJSON(data []byte) error {
	var raw struct {
		OldText    string `json:"old_text"`
		Search     string `json:"search"`
		NewText    string `json:"new_text"`
		Replace    string `json:"replace"`
		ReplaceAll bool   `json:"replace_all"`
	}
	if err := json.Unmarshal(data, &raw); err != nil {
		return err
	}
	e.OldText = raw.OldText
	if e.OldText == "" {
		e.OldText = raw.Search
	}
	e.NewText = raw.NewText
	if e.NewText == "" {
		e.NewText = raw.Replace
	}
	e.ReplaceAll = raw.ReplaceAll
	return nil
}

func (a EditFilesArgs) toSDKFiles() []workspacesdk.FileEdits {
	files := make([]workspacesdk.FileEdits, len(a.Files))
	for i, f := range a.Files {
		edits := make([]workspacesdk.FileEdit, len(f.Edits))
		for j, e := range f.Edits {
			edits[j] = workspacesdk.FileEdit{
				Search:     e.OldText,
				Replace:    e.NewText,
				ReplaceAll: e.ReplaceAll,
			}
		}
		files[i] = workspacesdk.FileEdits{
			Path:  f.Path,
			Edits: edits,
		}
	}
	return files
}

func EditFiles(options EditFilesOptions) fantasy.AgentTool {
	return fantasy.NewAgentTool(
		"edit_files",
		"Perform edits on one or more files by replacing old_text with"+
			" new_text. Matching is fuzzy (tolerates whitespace and indentation"+
			" differences) and preserves the file's existing indentation and"+
			" line endings. Errors if old_text matches zero locations, or more"+
			" than one unless replace_all is set. All edits in a batch are"+
			" validated before any file is written.",
		func(ctx context.Context, args EditFilesArgs, _ fantasy.ToolCall) (fantasy.ToolResponse, error) {
			var planPath string
			if options.IsPlanTurn && len(args.Files) > 0 {
				resolvedPlanPath, err := resolvePlanTurnPath(ctx, options.ResolvePlanPath)
				if err != nil {
					return fantasy.NewTextErrorResponse(err.Error()), nil
				}
				for i := range args.Files {
					args.Files[i].Path = strings.TrimSpace(args.Files[i].Path)
					if args.Files[i].Path != resolvedPlanPath {
						return fantasy.NewTextErrorResponse("during plan turns, edit_files is restricted to " + resolvedPlanPath), nil
					}
				}
				planPath = resolvedPlanPath
			}
			if options.GetWorkspaceConn == nil {
				return fantasy.NewTextErrorResponse("workspace connection resolver is not configured"), nil
			}
			conn, err := options.GetWorkspaceConn(ctx)
			if err != nil {
				return fantasy.NewTextErrorResponse(err.Error()), nil
			}
			if planPath != "" {
				if err := ensurePlanPathResolvesToItself(ctx, conn, planPath); err != nil {
					return fantasy.NewTextErrorResponse(err.Error()), nil
				}
			}
			return executeEditFilesTool(ctx, conn, args, options.ResolvePlanPath)
		},
	)
}

func executeEditFilesTool(
	ctx context.Context,
	conn workspacesdk.AgentConn,
	args EditFilesArgs,
	resolvePlanPath func(context.Context) (chatPath string, home string, err error),
) (fantasy.ToolResponse, error) {
	if len(args.Files) == 0 {
		return fantasy.NewTextErrorResponse("files is required"), nil
	}

	var (
		chatPath       string
		home           string
		planPathErr    error
		planPathLoaded bool
	)
	for i := range args.Files {
		args.Files[i].Path = strings.TrimSpace(args.Files[i].Path)
		file := args.Files[i]

		hasPlanFileName := looksLikePlanFileName(file.Path)
		if hasPlanFileName && !isAbsolutePath(file.Path) {
			return fantasy.NewTextErrorResponse(
				"plan files must use absolute paths; use the chat-specific absolute plan path; no files in this batch were applied",
			), nil
		}
		if resolvePlanPath == nil || !hasPlanFileName {
			continue
		}
		if !planPathLoaded {
			chatPath, home, planPathErr = resolvePlanPath(ctx)
			planPathLoaded = true
		}
		if resp, rejected := rejectSharedPlanPath(file.Path, home, chatPath, planPathErr); rejected {
			return fantasy.NewTextErrorResponse(
				resp.Content + "; no files in this batch were applied",
			), nil
		}
	}

	resp, err := conn.EditFiles(ctx, workspacesdk.FileEditRequest{
		Files:       args.toSDKFiles(),
		IncludeDiff: true,
	})
	if err != nil {
		return fantasy.NewTextErrorResponse(err.Error()), nil
	}
	return toolResponse(map[string]any{
		"ok":    true,
		"files": resp.Files,
	}), nil
}