///|
fn html_escape(s : String) -> String {
  s
  .replace_all(old="&", new="&")
  .replace_all(old="<", new="<")
  .replace_all(old=">", new=">")
  .replace_all(old="\"", new=""")
  .replace_all(old="'", new="'")
}

///|
fn tag(name : String, body : String) -> String {
  "<\{name}>\{body}"
}

///|
fn li(body : String) -> String {
  tag("li", body)
}

///|
fn html_section(title : String, items : Array[String]) -> String {
  tag("section", tag("h2", html_escape(title)) + tag("ul", items.join("")))
}

///|
fn input_html(i : ChemInput) -> String {
  let suffix = if i.note == "" { "" } else { " - \{html_escape(i.note)}" }
  li(
    "\{html_escape(i.name)}: \{html_escape(quantity_text(i.value))}\{suffix}",
  )
}

///|
fn assumption_html(a : Assumption) -> String {
  li("\{html_escape(a.title)}: \{html_escape(a.detail)}")
}

///|
fn formula_html(f : Formula) -> String {
  let vars = if f.variables.length() == 0 {
    ""
  } else {
    " \{html_escape(f.variables.join(", "))}"
  }
  li(
    "\{html_escape(f.name)}: \{html_escape(f.expression)}\{vars}",
  )
}

///|
fn result_html(r : ChemResult) -> String {
  let suffix = if r.procedure == "" {
    ""
  } else {
    " - \{html_escape(r.procedure)}"
  }
  li(
    "\{html_escape(r.name)}: \{html_escape(quantity_text(r.value))}\{suffix}",
  )
}

///|
fn warning_html(w : ReportWarning) -> String {
  let sev = severity_text(w.severity)
  li(
    "\{sev}: \{html_escape(w.message)}",
  )
}

///|
fn source_html(s : DataSource) -> String {
  let citation = html_escape(s.citation)
  let body = if s.url == "" {
    citation
  } else {
    "\{citation} \{html_escape(s.url)}"
  }
  li("\{html_escape(s.label)}: \{body}")
}

///|
pub fn ChemReport::to_html_fragment(self : ChemReport) -> String {
  let parts : Array[String] = [
    tag("h1", html_escape(self.title)),
    if self.summary == "" {
      ""
    } else {
      tag("p", html_escape(self.summary))
    },
    html_section("Inputs", [ for i in self.inputs => input_html(i) ]),
    html_section(
      "Assumptions",
      [
        for a in self.assumptions => assumption_html(a)
      ],
    ),
    html_section("Formulas", [ for f in self.formulas => formula_html(f) ]),
    html_section("Results", [ for r in self.results => result_html(r) ]),
    html_section("Warnings", [ for w in self.warnings => warning_html(w) ]),
    html_section("Data Sources", [ for s in self.sources => source_html(s) ]),
  ]
  parts.join("")
}

///|
pub fn ChemReport::to_html_document(self : ChemReport) -> String {
  "\{self.to_html_fragment()}"
}