package buildstep

import (
	"fmt"
	"path"
	"regexp"
	"strings"
)

var (
	requestCommitOK     = regexp.MustCompile(`^[0-9a-f]{40}$`)
	requestRepositoryOK = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._-]*/[A-Za-z0-9][A-Za-z0-9._-]*$`)
)

// FetchRequest is what a build module's fetch tool is asked: the repository and the full commit, the pull request's
// ref when only its head carries the commit, the trunk commit to merge onto for a merge preview, and, for a build of a
// module whose every artifact names its paths, that module's directory and its named paths (novox/hq ADR 0499 clause 4).
//
// **The paths come from the builder, not from a manifest** (ADR 0495 clause 1; the lead's decision L8 of R4e): the
// builder fills Dir and Paths from the indexer's Module value (Path, and KeptInputs2.Paths' keys), and the build module
// gives the build and test steps a workspace holding those paths, the manifest and its lock files. A request without
// them builds from the module's directory, as before.
type FetchRequest struct {
	Repository string   `json:"repository"`
	Commit     string   `json:"commit"`
	Ref        string   `json:"ref,omitempty"`
	Base       string   `json:"base,omitempty"`
	Dir        string   `json:"dir,omitempty"`
	Paths      []string `json:"paths,omitempty"`
}

// FetchRequestProperties are the JSON schema properties of FetchRequest's dir and paths, for a fetch tool's Input.
func FetchRequestProperties() map[string]any {
	return map[string]any{
		"dir": map[string]any{"type": "string", "description": "the module's directory in the repository (\".\" for its root), with paths"},
		"paths": map[string]any{"type": "array", "items": map[string]any{"type": "string"},
			"description": "the paths the module names, relative to dir, from the indexer's kept inputs: the build sees only these, the manifest and its lock files"},
	}
}

// Args is r as a tool call's arguments.
func (r FetchRequest) Args() map[string]any {
	args := map[string]any{"repository": r.Repository, "commit": r.Commit}
	for k, v := range map[string]string{"ref": r.Ref, "base": r.Base, "dir": r.Dir} {
		if v != "" {
			args[k] = v
		}
	}
	if len(r.Paths) > 0 {
		args["paths"] = append([]string(nil), r.Paths...)
	}
	return args
}

// ParseFetchRequest reads a fetch tool's arguments; arguments it does not know (a build module's own) are left to the
// caller. It refuses a repository that is not <owner>/<name>, a commit or a base that is not 40 hex digits, paths with no
// module directory or a directory with no path, a directory leaving the repository and a path leaving the directory,
// naming each.
func ParseFetchRequest(args map[string]any) (FetchRequest, error) {
	var r FetchRequest
	r.Repository, _ = args["repository"].(string)
	r.Commit, _ = args["commit"].(string)
	r.Ref, _ = args["ref"].(string)
	r.Base, _ = args["base"].(string)
	r.Dir, _ = args["dir"].(string)
	switch v := args["paths"].(type) {
	case nil:
	case []string:
		r.Paths = append([]string(nil), v...)
	case []any:
		for _, p := range v {
			s, ok := p.(string)
			if !ok {
				return FetchRequest{}, fmt.Errorf("paths is a list of strings")
			}
			r.Paths = append(r.Paths, s)
		}
	default:
		return FetchRequest{}, fmt.Errorf("paths is a list of strings")
	}
	return r, r.Check()
}

// Check is what ParseFetchRequest refuses.
func (r FetchRequest) Check() error {
	if !requestRepositoryOK.MatchString(r.Repository) || strings.Contains(r.Repository, "..") {
		return fmt.Errorf("%q is not a repository, <owner>/<name>", r.Repository)
	}
	if !requestCommitOK.MatchString(r.Commit) {
		return fmt.Errorf("%q is not a full commit (40 hex digits)", r.Commit)
	}
	if r.Base != "" && !requestCommitOK.MatchString(r.Base) {
		return fmt.Errorf("%q is not a trunk commit (40 hex digits)", r.Base)
	}
	switch {
	case len(r.Paths) > 0 && r.Dir == "":
		return fmt.Errorf("the request names paths and names no module directory (dir) they are relative to")
	case len(r.Paths) == 0 && r.Dir != "":
		return fmt.Errorf("the request names a module directory and no path")
	}
	if r.Dir != "" && (outside(r.Dir) || strings.HasPrefix(r.Dir, "/")) {
		return fmt.Errorf("the module directory %q leaves the repository", r.Dir)
	}
	for _, p := range r.Paths {
		if p == "" || strings.HasPrefix(p, "/") || outside(p) || path.Clean(p) == "." {
			return fmt.Errorf("the path %q leaves the module's directory or is not a path in it", p)
		}
	}
	return nil
}

func outside(p string) bool {
	c := path.Clean(p)
	return c == ".." || strings.HasPrefix(c, "../")
}