package accessctl

import (
	"fmt"
	"sort"

	"github.com/bmatcuk/doublestar"
)

var (
	// DefaultChangeAccessControl represents the ChangeAccessControl which is
	// applied when a changed file's path does not match any defined patterns
	// within a BranchAccessControl.
	DefaultChangeAccessControl = ChangeAccessControl{
		FilePathPattern: "**",
		Condition: Condition{
			Signature: &ConditionSignature{
				AnyAccount: true,
				Count:      "1",
			},
		},
	}

	// DefaultBranchAccessControls represents the BranchAccessControls which are
	// applied when the name of a branch being interacted with does not match
	// any defined patterns within the Config.
	DefaultBranchAccessControls = []BranchAccessControl{
		// These are currently the same, but they will differ once things like
		// comments start being implemented.
		{
			BranchPattern:        "main",
			ChangeAccessControls: []ChangeAccessControl{DefaultChangeAccessControl},
		},
		{
			BranchPattern:        "**",
			ChangeAccessControls: []ChangeAccessControl{DefaultChangeAccessControl},
		},
	}
)

// BranchAccessControl represents an access control object defined for the
// purpose of controlling who is able to perform what interactions with a
// branch.
type BranchAccessControl struct {
	BranchPattern        string                `yaml:"branch_pattern"`
	ChangeAccessControls []ChangeAccessControl `yaml:"change_access_controls"`
}

// ChangeAccessControl represents an access control object being defined in the
// Config for the purpose of controlling who is able to change which files.
type ChangeAccessControl struct {
	FilePathPattern string    `yaml:"file_path_pattern"`
	Condition       Condition `yaml:"condition"`
}

// MatchInteractions is used as an input to Match to describe all
// interactions which are being attempted on a particular Branch.
type MatchInteractions struct {
	// Branch is the name of the branch the interactions are being attempted on.
	// It is required.
	Branch string

	// FilePathsChanged is the set of file paths (relative to the repo root)
	// which have been modified in some way.
	FilePathsChanged []string
}

// MatchedChangeAccessControl contains information about a ChangeAccessControl
// which was matched in Match
type MatchedChangeAccessControl struct {
	ChangeAccessControl ChangeAccessControl

	// FilePaths contains all FilePaths to which this access control was found
	// to be applicable.
	FilePaths []string
}

// MatchResult is the result returned from the Match method.
type MatchResult struct {
	// BranchPattern indicates the BranchPattern field of the
	// BranchAccessControl object which matched the inputs.
	BranchPattern string

	// ChangeAccessControls indicates which ChangeAccessControl objects matched
	// the files being changed.
	ChangeAccessControls []MatchedChangeAccessControl
}

// Match takes in a set of access controls and a set of interactions taking
// place, and returns a MatchResult describing the access controls which should
// be applied to the interactions.
func Match(accessControls []BranchAccessControl, interactions MatchInteractions) (MatchResult, error) {
	var res MatchResult

	accessControls = append(accessControls, DefaultBranchAccessControls...)

	// find the applicable BranchAccessControl
	var branchAC BranchAccessControl
	{
		var ok bool
		var err error
		for i := range accessControls {
			ok, err = doublestar.Match(accessControls[i].BranchPattern, interactions.Branch)
			if err != nil {
				return res, fmt.Errorf("error matching branch %q to pattern %q: %w",
					accessControls[i].BranchPattern, interactions.Branch, err)
			} else if ok {
				branchAC = accessControls[i]
				break
			}
		}
		if !ok {
			panic(fmt.Sprintf("no patterns matched branch %q, which shouldn't be possible", interactions.Branch))
		}
		res.BranchPattern = branchAC.BranchPattern
	}

	// determine ChangeAccessControl for each path in FilesChanged
	{
		changeACs := append(branchAC.ChangeAccessControls, DefaultChangeAccessControl)
		acToPaths := map[ChangeAccessControl][]string{}
		for _, path := range interactions.FilePathsChanged {
			var ok bool
			var err error
			for _, ac := range changeACs {
				if ok, err = doublestar.PathMatch(ac.FilePathPattern, path); err != nil {
					return res, fmt.Errorf("error matching path %q to patterrn %q: %w",
						path, ac.FilePathPattern, err)
				} else if ok {
					acToPaths[ac] = append(acToPaths[ac], path)
					break
				}
			}
			if !ok {
				panic(fmt.Sprintf("no patterns matched change path %q, which shouldn't be possible", path))
			}
		}
		for ac, paths := range acToPaths {
			res.ChangeAccessControls = append(res.ChangeAccessControls, MatchedChangeAccessControl{
				ChangeAccessControl: ac,
				FilePaths:           paths,
			})
		}

		// sort result for determinancy
		sort.Slice(res.ChangeAccessControls, func(i, j int) bool {
			pi := res.ChangeAccessControls[i].ChangeAccessControl.FilePathPattern
			pj := res.ChangeAccessControls[j].ChangeAccessControl.FilePathPattern
			return pi < pj
		})
	}

	return res, nil
}