Parent Issue

Split from #145 — assertResourceAvailable() + buildResourceUrl() two-line pattern repeated 90 times in url_builder.ts — DRY violation.

This is Part 1 of 3. See also: Part 2 and Part 3 (issues to follow).

Scope — Part 1 Only

Create the private build() helper method and rewrite Systems (16) + Deployments (9) + Procedures (8) = 33 methods to delegate to it.

Context: State of the File After Dependencies

This issue is sequenced after #156 and #157 (#100 Parts 1 & 2), which remove assertResourceAvailable() from 72 per-ID methods. After those are done, the file has two patterns:

Pattern A — 15 list/create methods (guard retained):

getSystems(options?: SystemQueryOptions): string {
  this.assertResourceAvailable('systems');
  return this.buildResourceUrl('systems', undefined, undefined, options);
}

Pattern B — 72 per-ID methods (guard removed by #100):

getSystem(id: string, options?: QueryOptions): string {
  return this.buildResourceUrl('systems', id, undefined, options);
}

The build() helper must handle both patterns. The recommended approach: build() always calls assertResourceAvailable(), but per-ID methods simply bypass build() and continue calling buildResourceUrl() directly. Only the 15 list/create methods need build().

Alternative: build() takes an optional guard: boolean parameter, or we create two helpers (buildGuarded() for list/create, and the existing buildResourceUrl() for per-ID). The implementer should choose the cleanest approach.

Implementation

Step 1 — Create the build() helper:

/**
 * Guards resource availability and constructs the URL in one step.
 * Used by list/create methods that require the resource to be discovered.
 *
 * @param resourceType - The resource type key (e.g., 'systems', 'datastreams').
 * @param id - Optional resource ID.
 * @param subPath - Optional sub-path (e.g., 'schema', 'observations').
 * @param options - Optional query parameters.
 * @returns Fully constructed URL string.
 * @throws {EndpointError} If the resource type is not available.
 */
private build(
  resourceType: string,
  id?: string,
  subPath?: string,
  options?: QueryOptions
): string {
  this.assertResourceAvailable(resourceType);
  return this.buildResourceUrl(resourceType, id, subPath, options);
}

Step 2 — Rewrite 33 methods (3 resource types):

For list/create methods (guard needed):

// Before:
getSystems(options?: SystemQueryOptions): string {
  this.assertResourceAvailable('systems');
  return this.buildResourceUrl('systems', undefined, undefined, options);
}
// After:
getSystems(options?: SystemQueryOptions): string {
  return this.build('systems', undefined, undefined, options);
}

For per-ID methods (guard already removed by #100):

// Before:
getSystem(id: string, options?: QueryOptions): string {
  return this.buildResourceUrl('systems', id, undefined, options);
}
// After:
getSystem(id: string, options?: QueryOptions): string {
  return this.build('systems', id, undefined, options);
}

Wait — design decision needed here. If build() always calls assertResourceAvailable(), then wrapping per-ID methods in build() would RE-INTRODUCE the guard that #100 removed. Two approaches:

• Approach A: build() only used by list/create methods. Per-ID methods stay as buildResourceUrl() calls unchanged. This means Part 1 only touches ~6 list/create methods for these 3 types + creates build(). The 27 per-ID methods stay as-is.
• Approach B: build() takes an optional skipGuard flag. Per-ID methods pass skipGuard: true.
• Approach C: Per-ID methods also go through build(), but build() conditionally guards based on whether id is present (no id = collection method = guard needed; id present = per-ID = skip guard).

Recommended: Approach C — build() conditionally guards: if no id is passed, it calls assertResourceAvailable(); if id is present, it skips the guard. This makes ALL methods delegate to build() uniformly, and the guard logic lives in one place. This is the cleanest DRY outcome.

private build(
  resourceType: string,
  id?: string,
  subPath?: string,
  options?: QueryOptions
): string {
  if (!id) {
    this.assertResourceAvailable(resourceType);
  }
  return this.buildResourceUrl(resourceType, id, subPath, options);
}

With this design, all 33 methods in scope become return this.build(...) one-liners.

Methods to Rewrite (33)

Systems (16): getSystems, getSystem, createSystem, updateSystem, deleteSystem, getSystemDataStreams, getSystemControlStreams, getSystemDeployments, getSystemSamplingFeatures, getSystemProcedure, getSystemHistory, getSystemDetails, plus any other system-related methods.

Deployments (9): getDeployments, getDeployment, createDeployment, updateDeployment, deleteDeployment, getDeploymentSubdeployments, getDeploymentSystems, plus others.

Procedures (8): getProcedures, getProcedure, createProcedure, updateProcedure, deleteProcedure, getProcedureSystems, getProcedureDataStreams, plus others.

File to Modify

What NOT to Touch

• ❌ SamplingFeatures, Properties, Datastreams, Observations, ControlStreams, Commands — Parts 2 and 3
• ❌ Public method signatures — names, parameters, return types must remain identical
• ❌ JSDoc on public methods — preserve all documentation
• ❌ assertResourceAvailable() or buildResourceUrl() definitions
• ❌ Test files — existing tests must pass unchanged
• ❌ Any file outside url_builder.ts

Acceptance Criteria (Part 1)

• Private build() method added to CSAPIQueryBuilder
• All Systems methods (16) delegate to build()
• All Deployments methods (9) delegate to build()
• All Procedures methods (8) delegate to build()
• No direct this.assertResourceAvailable() calls remain in these 33 methods
• Guard behavior preserved: list/create methods still throw when resource not available
• Per-ID methods still work without guard (consistent with [SPLIT] assertResourceAvailable() overly strict for per-ID methods → #156 + #157 #100 fix)
• tsc --noEmit — zero errors
• npm test — all tests pass
• npm run lint — zero errors

Dependencies

Blocked by: #156, #157 (#100 Parts 1 & 2 — assert removal must be done first)
Blocks: Part 2, Part 3

References

• [SPLIT] assertResourceAvailable() + buildResourceUrl() DRY violation (87 methods) → #158 + #159 + #160 #145 — parent issue with full analysis and all 38 references
• #100 Part 1: Remove assertResourceAvailable from per-ID methods — Systems, Deployments, Procedures, SamplingFeatures (33 methods) #156, #100 Part 2: Remove assertResourceAvailable from per-ID methods — Properties, Datastreams, Observations, ControlStreams, Commands (39 methods) #157 — [SPLIT] assertResourceAvailable() overly strict for per-ID methods → #156 + #157 #100 split (assert removal) — must complete before this
• DEFERRED — getCommandStatus() uses string concatenation instead of buildResourceUrl() for query string (F45) #111 — getCommandStatus() concatenation — resolved in Part 3
• url_builder.ts lines 256–273 (buildResourceUrl), 355–365 (assertResourceAvailable)
• Phase 7 Scope & Split Assessment

Operational Constraints

⚠️ MANDATORY: Before starting work on this issue, review docs/governance/AI_OPERATIONAL_CONSTRAINTS.md.

Upstream Isolation Constraint

Per the upstream maintainer's comment on PR #136: url_builder.ts is within src/ogc-api/csapi/ — purely internal to the isolated CSAPI module.