package config

import (
	"fmt"
	"path/filepath"
	"strings"
)

type DistributorTemplateValues struct {
	LocationID      string
	ReportID        string
	RunID           string
	ArtifactGroup   string
	BatchOutputName string
	ValidStartDate  string
	ValidEndDate    string
	ValidStartTime  string
	ValidEndTime    string
	ValidStartStamp string
	ValidEndStamp   string
	BundleID        string
}

var distributorTemplateVariables = map[string]struct{}{
	"location_id":       {},
	"report_id":         {},
	"run_id":            {},
	"artifact_group":    {},
	"batch_output_name": {},
	"valid_start_date":  {},
	"valid_end_date":    {},
	"valid_start_time":  {},
	"valid_end_time":    {},
	"valid_start_stamp": {},
	"valid_end_stamp":   {},
}

var distributorIdempotencyTemplateVariables = map[string]struct{}{
	"location_id":       {},
	"report_id":         {},
	"run_id":            {},
	"artifact_group":    {},
	"batch_output_name": {},
	"valid_start_date":  {},
	"valid_end_date":    {},
	"valid_start_time":  {},
	"valid_end_time":    {},
	"valid_start_stamp": {},
	"valid_end_stamp":   {},
	"bundle_id":         {},
}

var distributorPipelineTemplateVariables = distributorIdempotencyTemplateVariables

func RenderDistributorBundleID(template string, values DistributorTemplateValues) (string, error) {
	return renderDistributorTemplate("notify.distributor.bundle_id_template", template, values, distributorTemplateVariables)
}

func RenderDistributorPipelineID(template string, values DistributorTemplateValues) (string, error) {
	rendered, err := renderDistributorTemplate("notify.distributor.pipeline_id_template", template, values, distributorPipelineTemplateVariables)
	if err != nil {
		return "", err
	}
	if strings.TrimSpace(rendered) == "" {
		return "", fmt.Errorf("notify.distributor.pipeline_id_template renders an empty pipeline id")
	}
	return rendered, nil
}

func RenderDistributorIdempotencyKey(template string, values DistributorTemplateValues) (string, error) {
	return renderDistributorTemplate("notify.distributor.idempotency_key_template", template, values, distributorIdempotencyTemplateVariables)
}

func RenderDistributorReportPaths(templates []string, values DistributorTemplateValues) ([]string, error) {
	if len(templates) == 0 {
		return nil, fmt.Errorf("notify.distributor.report_path_templates must contain at least one entry")
	}
	paths := make([]string, 0, len(templates))
	seen := make(map[string]struct{}, len(templates))
	for i, template := range templates {
		name := fmt.Sprintf("notify.distributor.report_path_templates[%d]", i)
		rendered, err := renderDistributorTemplate(name, template, values, distributorTemplateVariables)
		if err != nil {
			return nil, err
		}
		if err := ValidateDistributorReportPath(name, rendered); err != nil {
			return nil, err
		}
		if _, ok := seen[rendered]; ok {
			return nil, fmt.Errorf("notify.distributor.report_path_templates renders duplicate path %q", rendered)
		}
		seen[rendered] = struct{}{}
		paths = append(paths, rendered)
	}
	return paths, nil
}

func validateDistributorTemplate(name, template string, allowed map[string]struct{}) error {
	_, err := renderDistributorTemplate(name, template, DistributorTemplateValues{}, allowed)
	return err
}

func renderDistributorTemplate(name, template string, values DistributorTemplateValues, allowed map[string]struct{}) (string, error) {
	var rendered strings.Builder
	for i := 0; i < len(template); {
		switch template[i] {
		case '{':
			end := strings.IndexByte(template[i+1:], '}')
			if end < 0 {
				return "", fmt.Errorf("%s contains an unclosed template variable", name)
			}
			variable := template[i+1 : i+1+end]
			if variable == "" {
				return "", fmt.Errorf("%s contains an empty template variable", name)
			}
			if _, ok := allowed[variable]; !ok {
				return "", fmt.Errorf("%s contains unknown template variable %q", name, variable)
			}
			rendered.WriteString(distributorTemplateValue(variable, values))
			i += end + 2
		case '}':
			return "", fmt.Errorf("%s contains an unopened template variable", name)
		default:
			rendered.WriteByte(template[i])
			i++
		}
	}
	return rendered.String(), nil
}

func distributorTemplateValue(variable string, values DistributorTemplateValues) string {
	switch variable {
	case "location_id":
		return values.LocationID
	case "report_id":
		return values.ReportID
	case "run_id":
		return values.RunID
	case "artifact_group":
		return values.ArtifactGroup
	case "batch_output_name":
		return values.BatchOutputName
	case "valid_start_date":
		return values.ValidStartDate
	case "valid_end_date":
		return values.ValidEndDate
	case "valid_start_time":
		return values.ValidStartTime
	case "valid_end_time":
		return values.ValidEndTime
	case "valid_start_stamp":
		return values.ValidStartStamp
	case "valid_end_stamp":
		return values.ValidEndStamp
	case "bundle_id":
		return values.BundleID
	default:
		return ""
	}
}

func ValidateDistributorReportPath(name, path string) error {
	if path == "" {
		return fmt.Errorf("%s renders an empty path", name)
	}
	if isDistributorAbsolutePath(path) {
		return fmt.Errorf("%s must render a relative path", name)
	}
	if strings.Contains(path, "\\") {
		return fmt.Errorf("%s must not render backslashes", name)
	}

	segments := strings.Split(path, "/")
	for _, segment := range segments {
		if segment == "" {
			return fmt.Errorf("%s must not render empty path segments", name)
		}
		if segment == "." || segment == ".." {
			return fmt.Errorf("%s must not render . or .. path segments", name)
		}
		if segment == "manifest.json" || segment == ".distributor.json" {
			return fmt.Errorf("%s must not render reserved path segment %q", name, segment)
		}
	}

	return nil
}

func isDistributorAbsolutePath(path string) bool {
	if filepath.IsAbs(path) || strings.HasPrefix(path, "/") {
		return true
	}
	if len(path) >= 3 && isASCIIAlpha(path[0]) && path[1] == ':' && (path[2] == '/' || path[2] == '\\') {
		return true
	}
	return false
}

func isASCIIAlpha(ch byte) bool {
	return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z')
}