---
title: "Parsing SIU director's reports"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Parsing SIU director's reports}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
# the vignette runs in full in GitHub CI and for the package tarball (NOT_CRAN), on r-universe
# (MY_UNIVERSE), on the package website (IN_PKGDOWN) and in an interactive session; when CRAN
# re-builds it in its check, none of these is set and only this chunk runs
if (!interactive() && !any(nzchar(Sys.getenv(c("NOT_CRAN", "MY_UNIVERSE", "IN_PKGDOWN"))))) {
  knitr::knit_exit()
}
knitr::opts_chunk$set(collapse = TRUE, comment = "#>")
library(rmoriebricklayer)
```

Ontario's Special Investigations Unit publishes a director's report for every investigation
as an HTML page. The reports share a structure but not a template: fields appear under
varying headings, counts are written in words or figures, and the text is long. The package
parses them into a fixed, panel-reviewed schema with a parser written for hostile input.

## The schema

```{r siu-reports-schema}
sch <- siusch()
head(sch$name, 20)
nrow(sch)
```

## Parsing a report

The package ships a synthetic report with the structure of a real one and no real person
in it:

```{r siu-reports-parse}
f <- siuprs(system.file("extdata", "siu_synthetic_report.html",
                                      package = "rmoriebricklayer"))
f[["number_of_subject_officials"]]
f[["date_of_incident_iso"]]
```

## The pieces

HTML to plain text, with the layout tags turned into line structure and entities decoded:

```{r siu-reports-text}
siutxt("<p>Number of SIU Investigators assigned: 3</p>")
```

The subject-official count, resolved from the enumerated list rather than a headline number
that reports sometimes omit:

```{r siu-reports-so}
siuso("Subject Officials\nSO #1 Interviewed\nSO #2 Declined interview")
```

Dates in the report's prose, normalised to ISO:

```{r siu-reports-dates}
siudate("March 4, 2024")
siudate("not a date")
```

## Written for hostile input

A parser that reads 5,000 public web pages will meet broken HTML, megabyte-long lines,
unclosed tags and entities of every shape. Three review rounds on this parser established
and tested the following, each pinned by a test over the sources:

* **No regex crosses a line without a bound.** Two passes that once scanned to the end of the
  document on `[\s\S]*?` were replaced by `find()` scans after 44 KB of period-free
  boilerplate overflowed the C stack; a hygiene test now asserts no unbounded cross-line
  regex exists in the SIU sources.
* **Every pass is linear.** Two tag-stripping passes were quadratic (re-scanning from each
  unclosed `<script` or bare `<`); at the 2 MiB input cap one took 40 minutes. Both are
  single-pass now.
* **Lines are capped at 2,000 characters** and split at the last sentence end inside the
  window, else the last space; the functions warn how many lines were split, because a field
  spanning a split can come back incomplete.
* **Numbers are bounded.** Every string-to-integer conversion goes through one helper that
  reads up to nine digits; `SO #1234567` is 1234567, and `SO #4444444444444444` is ignored
  as a tag (the count falls back to the other cues),
  not an overflow.
* **The user can interrupt.** The whole path polls for an interrupt through a hook the host
  installs, and raises it only from a frame that owns no live C++ objects.
* **Input is capped at 2 MiB**, and the fuzzers run the parser under an 8 MB stack like R's,
  with seeds for every shape the reviewers used.

## Fetching live reports

`siufetch()` fetches a report by its identifier through the package's checked
transport (address validation, redirect policy, resource limits) with an Internet Archive
fallback, and `siufprs()` fetches and parses in one call:

```{r siu-reports-fetch, eval = FALSE}
f <- siufprs("24-OCI-123")
```

The corpus of parsed reports, reviewed round by round, is distributed as a dataset by the
companion package `rmoriedata`; this package provides the parser so the corpus can be
rebuilt and audited.


## Indigenous police services

Ontario's First Nations police services, among them the Nishnawbe-Aski Police Service, the
Anishinabek Police Service and the Treaty Three Police Service, are investigated by the SIU
like any other. The parsed `police_service` field selects their cases (this fetches live
reports, so it is not run here):

```{r siu-reports-indigenous-siu, eval = FALSE}
fnservices <- c("Nishnawbe-Aski Police Service", "Anishinabek Police Service",
                 "Treaty Three Police Service", "UCCM Anishnaabe Police Service")
reports <- lapply(reporturls, siufprs)
mine <- Filter(function(r) any(grepl(paste(fnservices, collapse = "|"), r$police_service)),
               reports)
length(mine)
```

## The report's timeline in a picture

`siuprs()` returns each date in the report in ISO form. Drawn on one axis, they give the
investigation's timeline at a glance.

```{r siu-reports-siu-timeline-plot, fig.width = 7, fig.height = 3.5}
rpt <- siuprs(siutxt(paste(readLines(system.file("extdata", "siu_synthetic_report.html",
                                                    package = "rmoriebricklayer"), warn = FALSE),
                           collapse = "\n")))
iso <- rpt[grepl("_iso$", names(rpt)) & grepl("^\\d{4}-\\d{2}-\\d{2}$", rpt)]
when <- as.Date(iso)
o <- order(when)
lab <- gsub("_", " ", sub("_iso$", "", names(iso)[o]))
span <- diff(range(when))
op <- par(mar = c(4, 1, 3, 1))
plot(when[o], seq_along(o), pch = 19, col = blpal()[1], yaxt = "n", xaxt = "n", xlab = "", ylab = "",
     xlim = range(when) + c(-0.1, 0.1) * as.numeric(span), ylim = c(0.5, length(o) + 0.5),
     main = "Dates in the synthetic report")
axis.Date(1, when, format = "%Y-%m-%d")
text(when[o], seq_along(o), paste0(lab, "  ", format(when[o])), cex = 0.75,
     pos = ifelse(seq_along(o) < length(o), 4, 2))
par(op)
```